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CL4.14

The Arctic Realm is changing rapidly and the fate of the cryosphere, including Arctic sea ice, glaciers and ice caps, is a source of concern. Whereas sea ice variations impact the radiative energy budget, thus playing a role in Arctic amplification, the Greenland Ice Sheet retreat contributes to global sea level rise. Moreover, through various processes linking the atmosphere, ice and ocean, the change in the Arctic realm may modify the atmospheric and ocean circulation at regional to global scales, the freshwater budget of the ocean and deep-water formation as well as the marine and terrestrial ecosystems. The processes and feedbacks involved operate on all time scales and thus require several types of information: satellite and instrumental data, climate models, and reconstructions based on geological archives. In this session, we invite contributions from a range of disciplines and across time scales, including observational data, historical data, proxy data, model simulations and forecasts, for the past, present and future climate. The common denominator of these studies will be their focus on a better understanding of mechanisms and feedbacks on short to long time scales that drive Arctic and subarctic changes and their impact on climate, ocean and environmental conditions, at regional to global scales, including possible links to weather and climate outside the Arctic.

Public information:
Dear participants in EGU 2020 session CL4.14,

Thanks you all for your various contributions to this session and for participating in the live chat. As this is a new form, we probably all wonder how well it will work, but we are also excited about trying out this new way of discussing our science!
None of the co-conveners have any experience in chats – and not the least managing them, so please accept our apologies if not everything will go as smoothly as we will like.

Process for the chat session:
Hopefully, you have all succeeded in uploading any display that you wish. However, also those who have chosen not to add any further material will still have the option to discuss your research based on your abstracts and any addition information that you can tell us.
Note: This chat is not recorded or stored. Only abstracts and further displays will be available after this session. This provides more freedom to discuss.
Also: All discussion will be in writing via the chat.
To best organize the chat session, we will carry out the chat for one presentation (display) at the time.
We (the conveners) will start up by writing the number of the display in the chat and invite the presenter to give a short introduction. Presenter: It would be advisable if you have a short text ready that you can upload in the chat box. Do not expect to give a full presentation, just give a SHORT introduction and highlight the main points. So, make it short, as we have many displays and people need time to read the chat messages. Do not just copy the entire abstract, as all session participants have had the possibility to read these prior to the chat session

After this short introduction to the presentation, the floor is now open for comments.
If no comments arrive within 30 seconds to 1 minute, we will move to the next display. Also, if no presenter is present for a display, we will also move on to the next display. One minute is a short time to write a detailed question, so it could be a good idea to prepare some comments beforehand.

Timing: We have up to 1h45min available for the session. With 27 presentations, this gives 3-4 minutes for each presentation. We did not succeed in getting a full overview of, who among the presenters, would like to discuss their result. Thus, currently we do not know how many presenters will be present or how much discussion each presentation will cause. Therefore, we need to keep a tight schedule but we will still try to be flexible, if there is a lively discussion. As there are some among the conveners who have indicated that they will likely not join the session, there should be some additional time, which at the first instance will be allocated to those, who have uploaded material in addition to abstracts – you will get 5 min for the discussion. Should there be time in the end after the full round of presentations/discussions, we can always return to discuss.

The chat session ends either when our time runs out or if the discussion ends.

All the best and keep safe,
Marit-Solveig Seidenkrantz, Anne de Vernal, Michal Kucera, Mimmi Oksman & Henrieka Detlef

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Co-organized by CR7/OS1
Convener: Marit-Solveig Seidenkrantz | Co-conveners: Anne de Vernal, Michal Kucera, Mimmi OksmanECSECS, Henrieka Detlef
Displays
| Attendance Mon, 04 May, 16:15–18:00 (CEST)

Files for download

Session materials Download all presentations (69MB)

Chat time: Monday, 4 May 2020, 16:15–18:00

Chairperson: Mimmi Oksman & Henrieka Detlef
D3856 |
EGU2020-3053
| Highlight
Steffen Hetzinger, Jochen Halfar, Zoltan Zajacz, Marco Möller, and Max Wisshak

The Arctic cryosphere is changing at a rapid pace due to global warming and the large-scale changes observed in the Arctic during the past decades exert a strong influence throughout the global climate system. The warming of Arctic surface air temperatures is more than twice as large as the global average over the last two decades and recent events indicate new extremes in the Arctic climate system, e.g. for the last five years Arctic annual surface air temperature exceeded that of any year since 1900 AD. Northern Spitsbergen, Svalbard, located in the High Arctic at 80°N, is a warming hotspot with an observed temperature rise of ~6°C over the last three decades indicating major global warming impacts. However, even the longest available datasets on Svalbard climatic conditions do not extend beyond the 1950s, inhibiting the study of long-term natural variability before anthropogenic influence. Ongoing climate trends strongly affect the state of both glaciers and seasonal snow in Svalbard. Modeled data suggest a marked increase in glacier runoff during recent decades in northern Svalbard. However, observational data are sparse and short and the potential effects on the surface ocean are unclear.
This study focuses on the ultra-high-resolution analysis of calcified coralline algal buildups growing attached to the shallow seafloor along Arctic coastlines. Analysis of these new annually-layered climate archives is based on the long-lived encrusting coralline algae Clathromorphum compactum, providing a historic perspective on recently observed changes. Here, we present a 200-year record of past surface ocean variability from Mosselbukta, Spitsbergen, northern Svalbard. By using algal Ba/Ca ratios as a proxy for past glacier-derived meltwater input, we investigate past multi-decadal-scale fluctuations in land-based freshwater contributions to the ocean surface layer. Our records, based on multiple coralline algal specimens, show a strong and statistically significant increasing trend in algal Ba/Ca ratios from the 1990s onwards, suggesting a drastic increase in land-based runoff at Mosselbukta. The drastic rate of increase is unprecedented during the last two centuries, directly capturing the impact of amplified surface air temperature warming on coastal high Arctic surface ocean environments.

 

How to cite: Hetzinger, S., Halfar, J., Zajacz, Z., Möller, M., and Wisshak, M.: Late 20th century increase in northern Svalbard glacier-derived runoff tracked by encrusting coralline algae, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3053, https://doi.org/10.5194/egusphere-egu2020-3053, 2020

D3857 |
EGU2020-12445
Ben Kopec, Eric Klein, David Noone, Hannah Bailey, Kaisa-Riikka Mustonen, Pete Akers, Jean-Louis Bonne, Martin Werner, Hans Chirstian Steen-Larsen, Sonja Wahl, Franziska Aemisegger, Bjorn Klove, Alun Hubbard, and Jeff Welker

MOSAiC is a one of a kind, year-long study of the Arctic Basin’s behavior focused in large part on interactions between sea ice, atmospheric processes, ecosystem dynamics and oceanography, as well as connections between the Arctic and the mid-latitudes. Our MOSAiC project is focused on how the Arctic Basin’s water cycle behaves throughout the year, especially now that sea ice loss allows for a new source of moisture to the atmosphere during times when this basin was formerly frozen over. These massive changes in open water and corresponding fluxes in conjunction with significant shifts in atmospheric circulation, are altering how moisture is transported into, within, and out of the Arctic Basin. In order to help quantify these Arctic hydrologic cycle variations, we have established the AWIN (Arctic Water Isotope Network) that uses continuous water vapor isotope measurements (δD, δ18O, and deuterium excess) at eight land-based stations from Barrow in Alaska to Ny Alesund in Svalbard, as well as on board the Polarstern.

With a network of sites rather than a single station, we gain the significant advantage of being able to track water vapor and how it varies from site to site, allowing us to identify the sources of moisture, and how and where that moisture is transported into, within, and out of the Arctic. For this analysis, we focus on the first months of the expedition (October-December 2019) to closely examine cases of critical events including a major low-pressure system in mid-November that impacted much of the Arctic Ocean basin and three key repeating transport regimes – 1) transport into the Arctic from the North Atlantic via the Greenland Sea, 2) transport into the Arctic via Baffin Bay, and 3) transport out of the Arctic via the Greenland Sea, as well as transport within the Arctic during each of these regimes. For example, in the scenario of transport into the Arctic via Baffin Bay, at our site in Thule, Greenland, we see significant reductions in deuterium excess each time the southerly flow initiates, suggesting significant moisture evaporating from nearby in Baffin Bay. We then can track that moisture to another site to observe how much of that locally-sourced vapor is transported to a given downwind location, allowing us to quantify vapor fluxes and isotopic fractionation processes across the Arctic. By examining these scenarios under varying sea ice conditions and large-scale atmospheric circulation patterns, this circum-Arctic network of water isotope measurements is transforming our understanding of the Arctic hydrologic cycle during MOSAiC.

How to cite: Kopec, B., Klein, E., Noone, D., Bailey, H., Mustonen, K.-R., Akers, P., Bonne, J.-L., Werner, M., Steen-Larsen, H. C., Wahl, S., Aemisegger, F., Klove, B., Hubbard, A., and Welker, J.: MOSAiC’s Pan Arctic Water Isotope Network: Sea ice-water vapor isotope interactions and transport processes within, into and out of the Arctic, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12445, https://doi.org/10.5194/egusphere-egu2020-12445, 2020

D3858 |
EGU2020-908
Natasha Roy, Bianca Fréchette, and Anne de Vernal

The rapid ongoing warming recorded across northern regions is unprecedented. This warming is however not uniform across the territory and large regional discrepancies exist. It is therefore relevant to document the variations of climate in the past in both time and space in order to understand the regional climate dynamics. However, in Labrador, instrumental and historical data are rare and only cover a short period of time. Our knowledge of the natural evolution of the climate is therefore limited, which hampers our capacity to evaluate the natural modes of variability and simulate changes at regional scales. From this viewpoint, quantitative climate reconstructions from pollen assemblages are useful because they allow the development of time series covering long periods of time. Here, we report on pollen data from peat and lake sediments collected in the area of Okak, Nain and Dog Island along the Labrador coast.  These data are used for climate reconstruction over the last millennia, thus allowing to document natural climate variability at regional scale. The climate parameters we reconstruct by the means of the modern analogue technique include the summer temperature, sunshine and precipitation. The results provide new insights about the climate of Labrador at local to regional scale, illustrating notably the importance of the Labrador Current on climatic conditions at nearshore locations. In fact, our climate reconstructions demonstrate a disparity with the regional climate curve which may testify of the east-west climatic gradient between islands and the land.

How to cite: Roy, N., Fréchette, B., and de Vernal, A.: Climate changes along the Labrador coasts during the Holocene based from pollen assemblages , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-908, https://doi.org/10.5194/egusphere-egu2020-908, 2019

D3859 |
EGU2020-21713
Lucie Menabreaz, Claude Hillaire-Marcel, Maccali Jenny, André Poirier, Bassam Ghaleb, and Evan Edinger

The Atlantic Meridional Overturning Circulation (AMOC) and the production rate of the North Atlantic Deep Water (NADW) are major components of the North Atlantic climate-system, with important hemispheric climatic influences. The post-glacial history of the AMOC, as reconstructed from Nd-isotopes (εNd) in biogenic minerals and sediments, demonstrates its sensitivity to freshwater fluxes, leading to concerns about its near-future response to the ongoing accelerated Greenland/Arctic ice melting. Whereas the early Holocene inception of the deep NADW components originating from the Nordic Seas has been well documented from such εNd-data, information on the status of its western, shallower and most sensitive component, the Labrador Sea Water (LSW), is still missing. New εNd-measurements in corals from the Labrador Slope provide the means to fill this gap. These data demonstrate that convection in the Labrador Sea was fully implemented by ca. 4 ka BP only, i.e., well after the final demise of the Laurentide ice-sheet. The time- and space-transgressive pattern of the full AMOC inception implies more complex driving mechanisms than meltwater fluxes only. Whereas the late Holocene neo-glacial cooling trend could have played here a minor role, the penetration and strengthening of the Irminger Current into the Labrador Sea has likely been the driving force.

How to cite: Menabreaz, L., Hillaire-Marcel, C., Jenny, M., Poirier, A., Ghaleb, B., and Edinger, E.: AMOC step-wise inception during the present interglacial recorded by Nd-isotopes. , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21713, https://doi.org/10.5194/egusphere-egu2020-21713, 2020

D3860 |
EGU2020-4699
Junjie Wu, Ruediger Stein, Kirsten Fahl, Nicole Syring, Jens Hefter, Gesine Mollenhauer, and Seung-il Nam

The Arctic is changing rapidly, and one of the main and most obvious features is the drastic sea-ice retreat over the past few decades. Over such time scales, observations are deficient and not long enough for deciphering the processes controlling this accelerated sea-ice retreat. Thus, high-resolution, longer-term proxy records are needed for reconstruction of natural climate variability. In this context, we applied a biomarker approach on the well-dated sediment core ARA04C/37 recovered in the southern Beaufort Sea directly off the Mackenzie River, an area that is characterized by strong seasonal variability in sea-ice cover, primary productivity and terrigenous (riverine) input. Based on our biomarker records, the Beaufort Sea region was nearly ice-free in summer during the late Deglacial to early Holocene (14 to 8 ka). During the mid-late Holocene (8 to 0 ka), a seasonal sea-ice cover developed, coinciding with a drop in both terrigenous sediment flux and primary production. Supported by multiple proxy records, two major flood events characterized by prominent maxima in sediment flux occurred near 13 and 11 ka. The former is coincident with the Younger Dryas Cooling Event probably triggered by a  freshwater outburst from the Lake Agassiz. The origin of the second (younger) one might represent a second Mackenzie flood event, coinciding with meltwater pulse IB/post-glacial flooding of the shelf and related increased coastal erosion. Here, our interpretation remains a little bit speculative, and further research is needed and also in progress.

How to cite: Wu, J., Stein, R., Fahl, K., Syring, N., Hefter, J., Mollenhauer, G., and Nam, S.: A 14 - 0 ka record of trends and events of sea ice cover, primary production and freshwater discharge in the Beaufort Sea, Arctic Ocean, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4699, https://doi.org/10.5194/egusphere-egu2020-4699, 2020

D3861 |
EGU2020-18268
Miriam C. Jones Jones, Max Berkelhammer, Katherine Keller, Kei Yoshimura, and Matthew J. Wooller

Anomalously low winter sea-ice extent and early retreat in CE 2018 and 2019 challenges previous notions of relatively stable winter sea ice in the Bering Sea over the instrumental record, but long-term sea-ice records from sediment proxies remain limited.  Here we use a record of peat-cellulose oxygen isotopes from St. Matthew Island, along with isotope-enabled general circulation model (IsoGSM) simulations to generate a 5,500-year record of Bering Sea winter sea-ice extent.  Results show that over the instrumental period (CE 1979-2018), oxygen isotope variability is largest over the late winter to spring (February, March, April, May [FMAM]) and highly correlated (-0.77, p<0.00001) with maximum winter sea-ice extent, months in which Bering sea ice reaches its winter maximum and then rapidly diminishes. We find that over the last 5,500 years, sea ice in the Bering Sea decreased in response to increasing winter insolation and atmospheric CO2, and on shorter, centennial timescales, small (<10 ppmv)  perturbations in atmospheric CO2, suggesting that the North Pacific is highly sensitive to small (<3 W m-2) changes in radiative forcing. However, we find that reconstructed sea-ice loss lags CO2 concentrations by ~120 years, indicating that the extremely anomalous recent conditions are a legacy of the early 20th century and that even with a complete cessation of greenhouse gas emissions today. As a consequence, the Bering Sea could lose all winter sea ice by mid-century, which it may not recover for millennia.

How to cite: Jones, M. C. J., Berkelhammer, M., Keller, K., Yoshimura, K., and Wooller, M. J.: High sensitivity of Bering Sea winter sea ice to winter insolation and carbon dioxide over the last 5,500 years, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18268, https://doi.org/10.5194/egusphere-egu2020-18268, 2020

D3862 |
EGU2020-3717
Glenn Rudebusch and Francis Diebold

The downward trend in the amount of Arctic sea ice is a key factor determining the pace and intensity of future global climate change. Diminished sea ice also has a wide range of other environmental and economic consequences. Based on several decades of satellite data, we provide statistical forecasts of Arctic sea ice extent during the rest of this century. The best fitting statistical model indicates that overall sea ice coverage is declining at an increasing rate. By contrast, average projections from the CMIP5 global climate models foresee a gradual slowing of Arctic sea ice loss even in scenarios with high carbon emissions. Our long-range statistical projections also deliver probability assessments of the timing of an ice-free Arctic. These results indicate almost a 60 percent chance of an effectively ice-free Arctic Ocean during some summer in the 2030s -- much earlier than the average projection from global climate models.

How to cite: Rudebusch, G. and Diebold, F.: Probability Assessments of an Ice-Free Arctic: Comparing Statistical and Climate Model Projections, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3717, https://doi.org/10.5194/egusphere-egu2020-3717, 2020

D3863 |
EGU2020-1113
Samira Samimi, Shawn Marshall, and Michael McFerrin

Mass loss from the Greenland Ice Sheet has increased in recent decades due to significant increases in surface melt and runoff. The fraction of summer melt retains as a liquid water or refreezes as it percolates into the underlying cold firn, acting as a buffer to the summer runoff. There are challenges to quantifying both infiltration and refreezing of meltwater in this complex heterogeneous cold firn and to understand the spatial variability of these processes. In this study we present continuous in situ measurements of near-surface temperature and dielectric permittivity, a proxy for volumetric water content, using TDR (Time Domain Reflectometry) methods in the percolation zone of the southern Greenland Ice Sheet. We established two observation sites near Dye 2 in April, 2016, excavating firn pits to depths of 2.2 and 5.3 m. The two sites are 650 m apart to quantify the percolation and refreezing of meltwater and to observe the spatial variability of these processes through summer 2016. Thermistor arrays were used to track the thermal signature of meltwater penetration in firn, through the effects of latent heat release when meltwater refreezes. Through the addition of TDR probes, we attempt to directly quantify meltwater volume as well as hydraulic conductivity of the near-surface snow and firn. An automatic weather station (AWS) configured for surface energy balance monitoring was also installed. AWS data were used to calculate the surface energy balance and model meltwater production. The melting front, characterized by 0°C conditions and direct evidence of liquid water, penetrated to a depth of between 1.8 and 2.1 m in summer 2016; at depths of 2.1 m and greater, temperatures remained below 0°C, there was no evidence of abrupt warming (i.e. latent heat release), and dielectric permittivities remained at their background levels. Meltwater penetrated several thick ice layers, but not until temperatures reached the melting point at these depths, implying that ice layers may transition to a permeable ‘slush’ layer, given enough conductive and latent heating, permitting progressive penetration of meltwater to depth. Firn temperatures (sub-zero conditions below ~2 m) appear to have been the main barrier to deep penetration of meltwater during summer 2016.

How to cite: Samimi, S., Marshall, S., and McFerrin, M.: Time-Domain Reflectometry Observations of Meltwater Percolation and Retention in the Firn Layer of the Greenland Ice Sheet , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1113, https://doi.org/10.5194/egusphere-egu2020-1113, 2019

D3864 |
EGU2020-909
Charles Brunette, Bruno Tremblay, and Robert Newton

Previous work shows that tracking the motion of sea ice in a Lagrangian framework can be used to produce skillful seasonal forecasts of sea ice at the pan-Arctic scale (Williams et al. 2016) and at the regional scale (Brunette et al. 2019) and can also be used to analyze socio-environmental impacts related to sea ice circulation (Newton et al. 2017). However, the Polar Pathfinder sea ice motion dataset from the National Snow and Ice Data Centre (Tschudi et al. 2019), which is commonly used for calculations of ice drift trajectories, contains biases in sea ice drift speed and angle. The bias is particularly strong in the summer when less satellite drift-vectors are available, and the Polar Pathfinder composite product relies more heavily on poorly-constrained free drift estimates (ice motion in response to wind forcing and ocean drag in the absence of internal stresses), that have up to a 60% low speed bias when compared to buoy drifts. These free drift estimates are notoriously ill-constrained, since information on the ocean forcing from below and lateral forces within the ice pack are lacking. To improve the quality of ice motion estimates in the summer, we propose to compile a new free drift sea ice motion dataset, based on surface winds from ERA-Interim and calibrated on drifting buoys from the International Arctic Buoy Program. We include dependencies of free drift velocity on sea ice concentration and thickness, which will improve the representation of temporal and spatial variability of sea ice in a free drift regime. We present work on the parameterization of an ice state dependent transfer coefficient between wind velocity and ice velocity, and estimates of the near surface oceanic currents that are necessary to constrain ice motion.

How to cite: Brunette, C., Tremblay, B., and Newton, R.: A new free drift sea ice velocity dataset for improved representations of ice drift trajectories, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-909, https://doi.org/10.5194/egusphere-egu2020-909, 2019

D3865 |
EGU2020-5215
Peiyan Xie, Hailun He, and Shuang Li

Since the 1950s, human has begun to explore the Arctic area. As the scientific research goes further, scientists gradually realize the important role the Arctic plays in the global climate system, and it has been said the Arctic has an amplifying effect on surface warming, which increases 2 to 3 times faster than the global average increment. Given the importance of this area, we try to figure out the relationship among the Arctic sea surface temperature (SST), sea ice index and the Arctic Oscillation (AO) in this paper. By using Community Earth System Model (CESM), we calculated an ocean-seaice-atmosphere coupled 200-year experiment. As a result, we found out that the variation of Arctic SST is negatively correlated with the change of sea ice area. There is a significant correlation between the change of SST and AO, which can lead to the anomaly of air heat transport between the Arctic area and the areas in lower latitude.

How to cite: Xie, P., He, H., and Li, S.: A Study on the Change of Arctic Ocean Surface Temperature in CESM, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5215, https://doi.org/10.5194/egusphere-egu2020-5215, 2020

D3866 |
EGU2020-13541
Sonja Murto, Rodrigo Caballero, and Gunilla Svensson

Atmospheric blockings are defined as quasi-stationary synoptic-scale systems of high pressure that can influence different weather events. Previous studies have examined the role of blockings in favoring intense poleward moisture transport into the Arctic and the role of polar anticyclones to Arctic sea-ice loss (e.g. Woods et al. 2013; Wernli & Papritz 2018). However, the mechanisms and theories for blocking formation and maintenance, in combination with their contributions to the Arctic climate, are yet not fully understood. This study presents a detailed northern hemisphere climatological analysis of large-scale patterns during 50 warm events of extreme wintertime (NDJFM) Arctic surface temperature anomalies, as defined by Messori et al. (2018), for the ERA-Interim period of 1979-2016. In contrast to the previous mentioned study, the main focus in this study is to relate the warm events with atmospheric blockings, identified as upper level anticyclonic PV anomalies following a dynamically-based blocking identification algorithm (Schwierz et al. 2004). In order to classify the events by their spatially and temporally varying blocking patterns, we calculate regional averages of the blocking frequencies for sector areas defined above 50 °N. General patterns and anomalies in meteorological variables in the different area clusters are quantified. Based on the blocking fractions for 90th and 95th percentiles, we can relate up to 80 % of the warm events to strong blockings. Additionally, we show that the remaining events obtain similar patterns, though with weaker or shorter-lived blocks. Overall, it can be conducted that almost all warm events in the clusters precede with a significant blocking located in the area around the Urals and the nearby parts of the Arctic Ocean. Despite the similarities found in the high Arctic for most of the events, there are different patterns identified in the periphery between the clusters. A North-Atlantic block is often found in the same cluster as with the Ural blocking, however with some temporal lag prior to the latter one. Therefore, the connection with the NAO-index during the warm events is also investigated. Our study gives a deeper insight into the large-scale patterns and emphasizes the importance of the large-scale settings prior to the Arctic warm events, primarily focusing on the importance of the atmospheric blockings. The formation of these blockings and the dynamical processes on different scales driving these warm events are further discussed using trajectory-analysis in an upcoming study. These two studies aim to improve the understanding of the preconditions needed for these Arctic warm events to occur and, furthermore, the mechanisms that control these events in high latitudes.

 

Woods, C., Caballero, R., & Svensson, G. (2013). Large-scale circulation associated with moisture intrusions into the Arctic during winter. Geophysical Research Letters, 40(17), 4717-4721.

Wernli, H., & Papritz, L. (2018). Role of polar anticyclones and mid-latitude cyclones for Arctic summertime sea-ice melting. Nature Geoscience, 11(2), 108.

Messori, G., Woods, C., & Caballero, R. (2018). On the drivers of wintertime temperature extremes in the High Arctic. Journal of Climate, 31(4), 1597–1618.

Schwierz, C., Croci-Maspoli, M. & Davies, H. C. 2004). Perspicacious indicators of atmospheric blocking. Geophys. Res. Lett. 31, L06125.

How to cite: Murto, S., Caballero, R., and Svensson, G.: Large-scale patterns preceding Arctic warm events, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13541, https://doi.org/10.5194/egusphere-egu2020-13541, 2020

D3867 |
EGU2020-10881
Brady Ferster, Alexey Fedorov, Juliette Mignot, and Eric Guilyardi

The Arctic and North Atlantic Ocean play a fundamental role in Earth’s water cycle, distribution of energy (i.e. heat), and the formation of cold, dense waters. Through the Atlantic meridional overturning circulation (AMOC), heat is transported to the high-latitudes. Classically, the climate impact of AMOC variations has been investigated through hosing experiments, where anomalous freshwater is artificially added or removed from the North Atlantic to modulate deep water formation. However, such a protocol introduces artificial changes in the subpolar area, possibly masking the effect of the AMOC modulation. Here, we develope a protocol where AMOC intensity is modulated remotely through the teleconnection of the tropical Indian Ocean (TIO), so as to investigate more robustly the impact of the AMOC on climate. Warming in the TIO has recently been shown to strengthen the Walker circulation in the Atlantic through the propagation of Kelvin and Rossby waves, increasing and stabilizing the AMOC on longer timescales. Using the latest coupled-model from Insitut Pierre Simon Laplace (IPSL-CM6), we have designed a three-member ensemble experiment nudging the surface temperatures of the TIO by -2°C, +1°C, and +2°C for 100 years. The objectives are to better quantify the timescales of AMOC variability outside the use of hosing experiments and the TIO-AMOC relationship.  In each ensemble member, there are two distinct features compared to the control run. The initial changes in AMOC (≤20 years) are largely atmospherically driven, while on longer timescales is largely driven by the TIO teleconnection to the tropical Atlantic. In the northern North Atlantic, changes in sensible heat fluxes range from 15 to 20 W m-2 in all three members compared to the control run, larger than the natural variability. On the longer timescales, AMOC variability is strongly influenced from anomalies in the tropical Atlantic Ocean. The TIO teleconnection supports decreased precipitation in the tropical Atlantic Ocean during warming (opposite during TIO cooling) events, as well as positive salinity anomalies and negative temperature anomalies. Using lagged correlations, there are the strongest correlations on scales within one year and a delayed response of 30 years (in the -2°C ensembles). In comparing the last 20 years, nudging the TIO induces a 3.3 Sv response per 1°C change. In summary, we have designed an experiment to investigate the AMOC variability without directly changing the North Atlantic through hosing, making way for a more unbiased approach to analysing the AMOC variability in climate models.

How to cite: Ferster, B., Fedorov, A., Mignot, J., and Guilyardi, E.: Sensitivity of the Atlantic meridional overturning circulation (AMOC) to the tropical Indian Ocean warming., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10881, https://doi.org/10.5194/egusphere-egu2020-10881, 2020

D3868 |
EGU2020-6908
Claude Hillaire-Marcel, Anne de Vernal, and Yanguang Liu

The Arctic Ocean is a major player in the climate system of the Northern Hemisphere due to its role vs albedo, atmospheric pressure regimes, and thermohaline circulation. It shows large amplitude variability from millennial, to decadal and seasonal time scales. At millennial time scales, two drastically distinct regimes prevail primarily in relation with ocean volume and sea level (SL) changes: A modern like system, with a high SL when the Arctic Ocean shelves are submerged and Bering Strait is opened vs a glacial one, with a low SL, when shelves are emerged and partly glaciated and Bering Strait is closed. In the modern system, large submerged shelves result in high productivity, high sea-ice production rates and sea ice-rafting deposition in the Central Arctic. Moreover, a fully open Bering Strait, with SL at the present elevation, contributes about 40% of the freshwater budget of the Arctic Ocean (Woodgate & Aagaard, 2005, doi:10.1029/2004GL021747), and supports Si fluxes of about 20 kmol.s-1 towards the Western Arctic (Torres-Valdés et al., 2013, doi:10.1002/jgrc.20063), thus impacting primary productivity. Under low SL conditions, the Arctic Ocean is linked exclusively to the North Atlantic, through practically a single gateway, that of Fram Strait. Sedimentation in the Central Arctic is then dominated ice-rafting deposition from icebergs, thus controlled by streaming and calving processes along surrounding ice sheets. Due to its shallowness (< 50 m), the Bering Strait gateway becomes effective at a very late stage of glacial to interglacial transitions but closes early during reverse climate trends. Sedimentary records from shelves North of Strait may provide information on the status of the gateway, so far, for the present interglacial. Clay minerals in cores from the northern Alaskan shelf (Ortiz et al., 2009, doi:10.1016/j.gloplacha.2009.03.020) and micropaleontological tracers from the Chukchi Sea southern shelf (present study) can be used to document the status of the gateway. Here, North Pacific microfossils transported by currents through the gateway demonstrate its full effectiveness at ca 6 ka BP, well after the insolation maximum of the early Holocene but when SL had reached its maximum postglacial elevation, with significant impacts on Arctic Ocean salinity, sea-ice cover and productivity.. This out-of-phase behavior of the Arctic Ocean may have impacted the North Atlantic and Northern Hemisphere climate system, as the openings and closings of Bering Strait constitute critical tipping points on this system, off out of phase with other parameters controlling more globally the climate of the Northern Hemisphere.

How to cite: Hillaire-Marcel, C., de Vernal, A., and Liu, Y.: Response/feedback of the Arctic Ocean in the Northern Hemisphere climate system: the sea-level joker, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6908, https://doi.org/10.5194/egusphere-egu2020-6908, 2020

D3869 |
EGU2020-16044
Marie Sicard, Masa Kageyama, Pascale Braconnot, and Sylvie Charbit

The Last Interglacial (129 – 116 ka BP) is a time period with a strong orbital forcing which leads to a different seasonal and latitudinal distribution of insolation compared to the present. In particular, these changes amplify the Arctic climate seasonality. They induce warmer summers and colder winters in the high latitudes of the Northern Hemisphere. Such surface conditions favour a huge retreat of the arctic sea ice cover.
In this study, we try to understand how this solar radiation anomaly spreads through the surface and impacts the seasonal arctic sea ice. Using IPSL-CM6A-LR model outputs, we decompose the surface energy budget to identify the role of atmospheric and oceanic key processes beyond 60°N and its changes compared to pre-industrial. We show that solar radiation anomaly is greatly reduced when it reaches the Earth’s surface, which emphasizes the role of clouds and water vapor transport.
The results are also compared to other PMIP4-CMIP6 model simulations. We would like to thank PMIP participants for producing and making available their model outputs.

How to cite: Sicard, M., Kageyama, M., Braconnot, P., and Charbit, S.: The impact of orbital forcing on the Arctic climate during the Last Interglacial simulated by the IPSL-CM6A-LR model, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16044, https://doi.org/10.5194/egusphere-egu2020-16044, 2020

D3870 |
EGU2020-17959
Rebecca Jackson, Anna Bang Kvorning, Christof Pearce, Marit-Solveig Seidenkrantz, and Sofia Ribeiro

Polynyas, areas of open water in the otherwise sea-ice dominated high Arctic, are vital oases for biological productivity, supporting a plethora of marine mammals and birds that in turn sustain indigenous communities. Polynyas are not, however, consistent features. Beyond the observational era, little to nothing is known about their past dynamics and equally, about their resilience to emerging changes in Arctic sea-ice conditions.

Recent paleoceanographic reconstructions of the North Water in northern Baffin Bay, the largest of the high Arctic polynyas, indicate that the polynya contracted in response to warm climatic intervals during the Holocene (e.g. Roman Warm Period). In contrast, the onset of stable North Water polynya formation acted to suppress northward incursion of warm Atlantic-sourced waters. This highlighted not only the sensitivity of polynyas to past climatic changes, but the role their formation plays in mediating water column dynamics and ocean circulation.

These new findings provided the rationale for the MSCA project ‘POLARC: High Arctic Polynyas in a Changing Climate’, to investigate the Holocene dynamics of other high Arctic polynyas forming off the east Greenland coast. New marine sedimentary archives and a multiproxy approach will be used to reconstruct productivity, sea-ice conditions and bottom water conditions, capturing a holistic view of these systems and their interaction with climatic and oceanographic variation during the Holocene (11,700 years BP to present). We present here preliminary paleoceanographic reconstructions of the Sirius Water, the first Holocene record from this polynya region, as well as plans for model-data comparisons in key polynya regions with the aim of constraining the past and better predicting the future of these phenomena.

How to cite: Jackson, R., Bang Kvorning, A., Pearce, C., Seidenkrantz, M.-S., and Ribeiro, S.: High Arctic Polynyas in a Changing Climate, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17959, https://doi.org/10.5194/egusphere-egu2020-17959, 2020

D3871 |
EGU2020-13231
Henriette Kolling, Ralph Schneider, Annalena Lochte, Kirsten Fahl, and Ruediger Stein

Understanding the Earth’s climate system and by that improving predictions of future changes are of utmost importance. A key player in this context is the global thermohaline ocean circulation, of which North Atlantic deep ocean convection is an essential component. Hence, one important region for deep ocean convection is the Labrador Sea, where the warm Gulf Stream meets cold polar waters in the Subpolar Gyre. Sea surface temperature and salinity play a major role in this convective process; two factors that influence these parameters are seasonal sea ice cover and freshwater inflow. During the early Holocene a major freshening in the Labrador Sea at 8.5 ka BP has been associated with the collapse of the Hudson Bay Ice Saddle (Lochte et al., 2019a). This collapse was triggered by a subsurface warming of the western Labrador Sea, linked to the strengthening of the Irminger and West Greenland Current that could have accelerated the ice saddle collapse. However, the role of sea ice in this process is yet unknown.

 

Here, we present a reconstruction of sea ice cover during the respective time interval, based on the organic biomarker IP25, a highly branched isoprenoid that is considered as a reliable proxy for past sea ice conditions. Actually, we apply the more advanced PIP25 sea ice index, together with other biomarkers for phytoplankton productivity, to reconstruct sea ice changes at centennial scale for the early to mid Holocene from a Labrador Shelf sediment core.

 

Based on this approach we infer that nearly perennial sea ice cover opened towards more seasonally, extremely fluctuating, conditions around 8.5 ka, parallel to the strengthening of Atlantic warm water inflow towards the Labrador Shelf. The shift to more seasonal sea ice cover may have favoured the advance of Atlantic water into Hudson Bay and could have accelerated the collapse and subsequent drainage of the Hudson Bay Ice Saddle. The opening of the sea ice triggered phytoplankton productivity and we find evidence for the establishment of a stable ice edge in the vicinity of the core location between 8.1 and 7.6 ka. With the establishment of the Labrador Sea Water formation around 7.4 ka (Lochte et al., 2019b) sea ice continued to fluctuate seasonally and reduced freshwater inflow favoured enhanced phytoplankton productivity.

 

References:

Lochte, A. A., Repschläger, J., Kienast, M.,Garbe-Schönberg, D., Andersen, N., Hamann, C., Schneider, R., 2019a. Labrador Sea freshening at 8.5 ka BP caused by Hudson Bay Ice Saddle collapse. Nature Communications, 10-586

Lochte, A. A., Repschläger, J., Seidenkrantz, M-S., Kienast, M., Blanz, T., Schneider, R.R., 2019b. Holocene water mass changes in the Labrador Current. The Holocene 1-15

How to cite: Kolling, H., Schneider, R., Lochte, A., Fahl, K., and Stein, R.: Early to mid-Holocene sea ice changes on the Labrador Shelf - biomarker evidence., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13231, https://doi.org/10.5194/egusphere-egu2020-13231, 2020

D3872 |
EGU2020-880
Estelle Allan, Anne de Vernal, Marit-Solveig Seidenkrantz, Claude Hillaire-Marcel, Christof Pearce, Lorenz Meire, Hans Røy, Anders Møller Mathiasen, Mikkel Thy Nielsen, Jane Lund Plesner, and Kerstin Perner

Palynomorph analysis of marine cores raised off Nuuk (southwestern Greenland) provided records of sea-surface conditions and climate-ocean-ice dynamics at centennial resolution over the last 12,000 years. Transfer functions using dinocyst assemblages provided information about the sea-ice cover, seasonal sea-surface temperature (SST) and salinity (SSS), as well as primary productivity. At about 10,000 cal. years ago, an increase in species diversity and the rapid increase of phototrophic taxa (light-dependent), marks the onset of interglacial conditions, with summer temperature increasing up to ~10°C during the Holocene Thermal Maximum (HTM). Low SSS and high productivity conditions are recorded during the interval, which we associate to increased meltwater and nutrient input from the Greenland Ice Sheet. After ~5000 cal. years BP, the decrease of phototrophic taxa marks a two-steps cooling associated with the Neoglacial trend. Since ~2000 cal. years BP, an increase in the high-frequency variability of sea surface conditions is noticeable. The second step change towards colder and more unstable conditions starting about 3000 cal. years BP coincides with the disappearance of the Saqqaq culture. The gap of human occupation in western Greenland, between the Dorset and the Norse settlements, i.e., from ca. 2000 to 1000 cal. years BP, may thus be linked to the highly unstable conditions in surface waters.

How to cite: Allan, E., de Vernal, A., Seidenkrantz, M.-S., Hillaire-Marcel, C., Pearce, C., Meire, L., Røy, H., Mathiasen, A. M., Nielsen, M. T., Plesner, J. L., and Perner, K.: Land-Ocean interactions at the southwest Greenland margin during the Holocene , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-880, https://doi.org/10.5194/egusphere-egu2020-880, 2019

D3873 |
EGU2020-786
Lina Madaj, Claude Hillaire-Marcel, Friedrich Lucassen, and Simone Kasemann

Marine sediments from the West Greenland margin represent high-resolution archives of Holocene climate history, past ice sheet dynamics, changes in meltwater discharge and coastal current intensities. We investigate potential changes of sediment provenances using strontium (Sr) and neodymium (Nd) radiogenic isotopes as tracers for the origin and pathways of the silicate detrital fraction in marine sediments. Meltwater discharge and coastal currents are the most important transport pathways for detrital sediments into (northeast) Labrador Sea, which is an important pathway for freshwater from the Arctic Ocean and meltwater from the Greenland Ice Sheet to enter the North Atlantic, where deep water formation takes place. Variations in freshwater supply into Labrador Sea may influence deep water formation and therefore further circulation and climate patterns on a global scale.

The marine sediment record collected in Nuuk Trough, southwest Greenland, displays uniform isotopic compositions throughout most of the Holocene, indicating well mixed detrital material from local sources through meltwater discharge and distal sources transported via the West Greenland Current. From around 4 ka BP to present the composition of Nd isotopes reveals a steep (εNd: -29 to -35) and the Sr isotope composition a slight (87Sr/86Sr: 0.723 to 0.728) but pronounced shift. This time interval coincides with the transition into the Neoglacial time period [1], which is characterized by a significant drop in atmospheric temperatures [2], and the onset of the modern Labrador Sea circulation pattern (e.g. [3]). We suggest that the shift in Nd and Sr isotopes indicates a change towards less distal and more local sediment sources, possibly caused by enhanced erosion of the local bedrock during Neoglacial ice advance [4], along with a decrease in meltwater discharge [5] and coastal current strength, leading to a sediment delivery shift.

[1] Funder & Fredskild (1989) Quaternary geology of Canada and Greenland, 775–783. [2] Seidenkrantz et al. (2007) The Holocene 17, 387-401. [3] Fagel et al. (2004) Paleoceanography 19, PA3002. [4] Funder et al. (2011) Developments in Quaternary Sciences 15, 699-713, (and references therein). [5] Møller et al. (2006) The Holocene 16, 685-695.

How to cite: Madaj, L., Hillaire-Marcel, C., Lucassen, F., and Kasemann, S.: Neoglacial Ice Advance and Sediment Provenance Changes in Southwest Greenland and its Marginal Seas Traced by Radiogenic Isotopes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-786, https://doi.org/10.5194/egusphere-egu2020-786, 2019

D3874 |
EGU2020-3103
Antoon Kuijpers, Marit-Solveig Seidenkrantz, Ralph Schneider, Camilla S. Andresen, Signe Hygom Jacobsen, Mimmi Oksman, Lisa C. Orme, Jian Ren, and Sandrine Solignac

Knowledge of the impact of past climate warming on Greenland Ice Sheet stability is an important issue for assessing  thresholds that are critical for a potential ice sheet collapse. For the late Holocene, evidence has recently been found of a so-called 4.2 ka BP event(1) including a prominent warming spike in several ice core records from Greenland and Canada (Agassiz).  Also lake records from both Northwest(2) and South Greenland(3) support pronounced summer warming during that time. After c. 4.0 ka BP NW Greenland July air temperature dropped by about 3o C. Coeval with this exceptional atmospheric warming anomaly over northern Canada and parts of Greenland, abrupt cooling and freshening affected  the N-Atlantic subpolar gyre where Labrador Sea deep convection ceased(4). Northern N-Atlantic climate generally deteriorated. With our contribution we present Holocene sub-bottom profiling  and sedimentary shelf and  fjord records from Southwest Greenland and Disko Bay that indicate exceptional Greenland Ice Sheet melting 4.4-4.0 ka BP at a rate and magnitude not recorded since early Holocene deglaciation. Extremely strong melt water discharge resulted in erosion of fjord sediments(5) and local deposition of up to several meters thick meltwater sediment on the shelf(6-8).  Timing of this melting event corresponds to a significant anomaly in hydrographic parameters of the Labrador Current off Newfoundland(9,10), which is concluded to have resulted in thermohaline perturbation of the N-Atlantic Subpolar gyre.   

  • (1) Weiss, H. 2019. Clim Past doi:10.5194/cp-2018-162-RC2
  • (2) McFarlin, J.M. et al. 2018. PNAS doi:10.1073/pnas.1720420115
  • (3) Andresen, C.S. et al. 2004. J Quat Sci 19(8) doi:10.1002/jqs.886
  • (4) Klus, A. et al. 2018. Clim Past doi:10.5194/cp-14-1165-2018
  • (5) Ren, J. et al. 2009. Mar Micropal doi:10.1016/j.marmicro.2008.12.003
  • (6) Hygom Jacobsen, S. 2019. Master Thesis Aarhus Univ, Dept. of Geoscience, pp105
  • (7) Schneider, R. 2015. Cruise Rep epic.awi.de/id/eprint/37062/131/msm-44-46-expeditionsheft.pdf
  • (8) Kuijpers, A. et al. 2001. Geol. Greenland Surv Bull 189, 41-47
  • (9) Solignac, S. et al. 2011. The Holocene, doi: 10.1177/0959683610385720
  • (10) Orme, L. et al 2019. The Holocene (submitted)

How to cite: Kuijpers, A., Seidenkrantz, M.-S., Schneider, R., S. Andresen, C., Hygom Jacobsen, S., Oksman, M., C. Orme, L., Ren, J., and Solignac, S.: Late Holocene thermohaline perturbation of the N-Atlantic Subpolar Gyre linked to exceptional Greenland Ice Sheet melting between 4.4 and 4.0 ka BP , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3103, https://doi.org/10.5194/egusphere-egu2020-3103, 2020

D3875 |
EGU2020-169
Joanna Davies, Anders Møller Mathiase, Christof Pearce, and Marit-Solveig Seidenkrantz

The Arctic region exhibits some of the most visible signs of climate change globally. Arctic sea ice extent and volume has been declining sharply in recent decades; observations indicate a mean annual decrease of 3.2% since 1980. However, no extensive network of sea ice observations extends back further than the mid-18th century and satellite data since the late 1970s; this limits perspectives of sea ice variability on longer time scales. Thus, to understand the processes governing sea-ice cover and variability, predict how sea ice and ocean conditions will respond to anthropogenic climate change and to understand if the shrinking of Arctic sea ice is a unique and irreversible process, longer records of sea ice variability and oceanic conditions are required.

A multi-proxy approach, involving grain size, geochemical, foraminifera and sedimentary analysis, was applied to a marine sediment core from North East Greenland to reconstruct changes in sea ice extent and palaeoceanographic conditions throughout the early Holocene (ca. 12,400-7,800 cal. yrs. BP). The study aimed to improve the understanding of the interaction between ocean circulation, sea ice and fluctuations of the Zachariae Isstrøm (ZI), one of the main glacier outlets of NE Greenland. Four distinct zones have been identified: Zone 1 (12,400-11,600 cal. yrs. BP) covering the transition from the Younger Dryas into the Holocene which evidences a gradually warming climate, resulting in a retreat of the ZI; Zone 2 (11,600 – 10,300 cal. yrs. BP) which encapsulates two distinct cooling events as a result of cooler surface waters, rapid release of freshwater and local feedback mechanisms. This coincides with sudden re-advances of the ZI followed by gradual retreats; 3) Zone 3 (10,300 – 8,600 cal. yrs. BP) shows warm and stable conditions, with warm surface waters that resulted in the retreat of the ZI; 4) Zone 4 (8,600 – 7,800 cal. yrs. BP) which shows a rapid return to cooler conditions, with cold surface waters and rapid freshwater outbursts resulting in the re-advance of the ZI, forced by decreasing solar insolation and cold surface waters. Our investigation thus indicated that changes in oceanic conditions at the NE Greenland shelf had a significant impact on the extent and melting rate of the ZI glacier.

How to cite: Davies, J., Møller Mathiase, A., Pearce, C., and Seidenkrantz, M.-S.: Early Holocene history of the Zachariae Ice Stream, NE Greenland: Evidence from geochemistry, grain size and sedimentary parameters, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-169, https://doi.org/10.5194/egusphere-egu2020-169, 2019

D3876 |
EGU2020-5473
Nicole Syring, Ruediger Stein, Jeremy M. Llyod, Kirsten Fahl, Maximilian Vahlenkamp, Marc Zehnich, Robert Spielhagen, and Frank Niessen

Understanding the processes controlling the natural variability of sea ice in the Arctic, one of the most dynamic components of the climate system, can help to constrain the effects of future climate change in this highly sensitive area. For the first time, a detailed multi-proxy study was carried out to reconstruct past sea-ice variability off eastern North Greenland. This area is strongly influenced by cold surface waters and drift ice transported via East Greenland Current, meltwater pulses from the outlet glaciers of the Northeast Greenland Ice Stream, the build-up of landfast ice, and the formation of the Northeast Water Polynya. For our study, we have used well-dated sedimentary sections of Kastenlot Core PS93/025 and Gravity Core PS100/270. These sites are ideally suited to identify and disentangle the driving mechanisms of sea-ice distribution in the western Fram Strait. As proxies for the reconstruction of sea-ice cover we have used the sea-ice proxy IP25, a highly branched isoprenoid (HBI) monoene with 25 carbon atoms, in combination with specific open-water phytoplankton and terrestrial higher land plant biomarkers as well as specific microfossils (e.g., diatoms). Based on these high-resolution data sets we are able to reconstruct sea-ice variability, primary productivity, terrigenous input and seasonal formation of the NEW Polynya that evolved during the Holocene at the eastern North Greenland shelf.

The presence of IP25 throughout the core PS93/025 confirms that there has been seasonal sea ice in the area during the entire Holocene time interval. Our biomarker proxies indicate relatively rapid changes in sea-ice conditions at ~9 ka and ~1 ka, i.e., sea-ice conditions progressed through three major stages over the course of the Holocene. During the early Holocene we recorded a reduced, but variable sea-ice cover. Between about 9.3 and 5.5 ka, sea-ice coverage increased towards seasonal conditions. Based on terrigenous biomarkers and IRD we assume a stronger regional than local sea-ice signal at core site PS93/025, due to the high influence of drift ice transported from the central Arctic Ocean along the eastern North Greenland shelf. During the late Holocene, especially during the last 1 ka, our records reflect the seasonal formation of the NEW Polynya leading to stable sea-ice edge conditions and a fully developed polynya situation. Probably, cyclic changes in the solar activity acted as trigger for the short-term variability in sea-ice cover during Holocene times.

How to cite: Syring, N., Stein, R., Llyod, J. M., Fahl, K., Vahlenkamp, M., Zehnich, M., Spielhagen, R., and Niessen, F.: Holocene biomarker- and microfossil-based sea-ice reconstructions off the eastern North Greenland continental shelf (western Fram Strait), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5473, https://doi.org/10.5194/egusphere-egu2020-5473, 2020

D3877 |
EGU2020-4818
Robert F. Spielhagen and Andreas Mackensen

We use stable isotope data from different morphotypes of the polar species Neogloboquadrina pachyderma in a sediment core from the NE Greenland continental margin (79°N) as proxies for the variability of salinity, ice coverage, and bioproductivity/carbon fluxes. Stable oxygen and carbon isotopes (d18O, d13C) were measured on both thin- and thick shelled specimens of planktic foraminifers N. pachyderma. Since this species is known to attain the thick carbonate crust of adult specimens in deeper water, the isotopic difference between thick-shelled (morphotypes 1 and 2, according to Eynaud, 2011) and thin-shelled specimens (morphotypes 4 and 5) is proposed to reflect the salinity difference between subsurface and near-surface waters. In Late Glacial sediments only minor d18O differences between the morphotypes suggest an upper water mass structure with only minor salinity differences. The high d13C difference of >0.5‰ is ascribed to strong quantitative differences in the decomposition of isotopically light organic carbon within the upper water column (likely from intense ice coverage and reduced bioproductivity) which precludes that the d18O similarities merely result from a reduced vertical migration activity of the foraminifers. After 13 ka, a series of d18O spikes (amplitudes >1.5‰ in morphotypes 4/5) preserved in laminated sediments reflects a strong freshwater event at the NE Greenland margin, likely related to the export of freshwater from the Arctic Ocean and/or the decay of the nearby outer Greenland Ice Sheet. Within these spikes, d18O and d13C differences of N. pachyderma morphotypes reach maximum values, pointing at extreme salinity differences in the upper few hundred meters of the water column and likely high portions of isotopically light dissolved inorganic carbon from terrestrial sources (meltwater). In the Holocene, d18O differences are reduced to ca. 0.5‰ and relatively low d13C differences may indicate an activity of organic carbon decomposition reaching significantly deeper in the water column than in the glacial and deglacial, possibly related to a more open ice cover, enhanced bioproduction and higher C fluxes.

Reference

Eynaud, F., 2011. Planktonic foraminifera in the Arctic: potentials and issues regarding modern and quaternary populations. IOP Conf. Series, Earth and Environmental Science 14, 012005, doi:10.1088/1755-1315/14/1/012005

How to cite: Spielhagen, R. F. and Mackensen, A.: Variability of ocean stratification, sea ice coverage and bioproduction off NE Greenland in the Late Glacial to Holocene reconstructed from planktic foraminifer morphotypes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4818, https://doi.org/10.5194/egusphere-egu2020-4818, 2020

D3878 |
EGU2020-534
Katrina Kalavichchi and Igor Bashmachnikov

This study investigates the mechanism of positive feedback in the Barents Sea region, using the results of reanalyses from 1993 to 2014. Vertical heat fluxes, wind and pressure fields are obtained from OAFlux and ERA-Interim databases, the water temperature and currents from the ARMOR-3D database.

Oceanic heat transport was computed through three sections-at the entrance to the Barents Sea (BSO), in the southern part of the Norwegian sea and in the west of Spitsbergen. The results show that, during the study period, the oceanic heat flux through BSO was rapidly increasing, significantly faster than in the northwards heat transport in the Norwegian Sea. west of Spitsbergen, a negative linear trend was observed, indicating a redistribution of the increasing transport of the Atlantic Water into the Nordic Seas.

Based on reanalyses data, we show the tight relationship between the current velocities through the BSO and the change in the gradient of the zonal component of wind velocity. The variability of the atmospheric circulation and the variability of the convergence of atmospheric heat fluxes for the studied region was also assessed.

The results also show that, in winter, with increasing oceanic heat flux through the BSO, the turbulent heat fluxes in the southwestern part of the sea decreased, and the northern part of the sea and west of Novaya Zemlya increased. In the annual means, the increasing heat flux from the ocean to the atmosphere is due to a retreat of the ice edge and an increase in the ice-free area of the sea. The sea-surface atmospheric pressure also increased over the water area, with a maximum changes in the south-east of the sea.

For the years with the maximum oceanic winter heat fluxes into the Barents Sea, the atmospheric heat flux across the southern boundary increased, while it across the northern border weakened. The convergence of the atmospheric heat fluxes increased only at the sea surface (1000-975 hPa), whereas above (975-100 hPa) the convergence decreased, and the total atmospheric heat convergence varies out of phase with that of the ocean.

This study was supported by the Russian Science Foun- dation, project no. 17-17-01151.

How to cite: Kalavichchi, K. and Bashmachnikov, I.: Ocean-Atmosphere positive feedback in the Barents Sea region with reanalyses data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-534, https://doi.org/10.5194/egusphere-egu2020-534, 2019

D3879 |
EGU2020-7894
Martin Klug, Karl Fabian, Jochen Knies, Valérie Bellec, and Leif Rise

Holocene climate variability and environmental changes have been studied using a sediment record from the Barents Sea with focus on the spatio-temporal evolution of bio-productivity and terrestrial sediment deposition in response to changes of climate and regional oceanography. From a 3 m long sediment core recovered in the South-Eastern Barents Sea at 72.5°N 32.5°E u-channels were extracted and stepwise demagnetized and measured for their natural remanent magnetization (NRM) and anhysteretic remanent magnetization (ARM) at the cryogenic magnetometer facility at the Geological Survey of Norway. The u-channel measurements at 3 mm resolution allow the reconstruction of palaeoinclination, relative declination and relative palaeointensity. Comparison of these parameters to FENNOSTACK (Snowball et al., 2007) and EGLACOM-SVAIS (Sagnotti et al., 2011) establishes a robust age model for the sediment sequence which otherwise contains little datable material. We applied statistical factor analysis as centred logratio (clr) transformation to reduce dimensionality of the XRF data and compare changes in high-resolution magnetic susceptibility, wet bulk density and XRF elemental composition with changes of climate proxies in other North Atlantic sedimentary records.

Based on the new chronostratigraphic framework changes of inorganic and organic proxies at long-term and sub-millennial scale resolve the temperature variability throughout the Holocene. Calcium content changes are related to regional bio-productivity changes in response to surface temperature changes with a pronounced deterioration at the beginning of the Neoglaciation and gradual enhancement during the late Holocene. Besides palaeoclimatic responses, the results offer the opportunity to study sediment transport and deposition during the regional deglaciation and mid-Holocene glacier growth in northwestern Fennoscandia. The temporal changes of the regional oceanography and the variability of marine palaeoproductivity in the South-Eastern Barents Sea indicate an active interplay between the North Atlantic Current (NAC) and the Norwegian Coastal Current (NCC) during the early Holocene, a predominance of the NCC during middle Holocene and a re-amplification of the NAC during the late Holocene. Comparison to other records from the Nordic Seas enables the reconstruction of responses and the vulnerability of this arctic marine ecosystem to past climate variations and may help to estimate upcoming responses to recent and future climate changes.

 

References:

Snowball, I., L. Zillén, A. Ojala, T. Saarinen, and P. Sandgren (2007), FENNOSTACK and FENNORPIS: Varve dated Holocene palaeomagnetic secular variation and relative palaeointensity stacks for Fennoscandia, Earth and Planetary Science Letters, 255, (1-2), 106–116

Sagnotti, L., P. Macrì, R. Lucchi, M. Rebesco, and A. Camerlenghi (2011), A Holocene paleosecular variation record from the northwestern Barents Sea continental margin, Geochemistry, Geophysics, Geosystems, 12, (11)

How to cite: Klug, M., Fabian, K., Knies, J., Bellec, V., and Rise, L.: Holocene climatic and palaeoenvironmental changes in the South-Eastern Barents Sea – new insights from palaeomagnetic and geochemical stratigraphy, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7894, https://doi.org/10.5194/egusphere-egu2020-7894, 2020

D3880 |
EGU2020-20778
Martin Schulthess, Jacqueline Otto, Ellen Berntell, and Qiong Zhang

Frontal ablation processes and resulting mass loss at tidewater glaciers are a key uncertainty in future predictions of sea level rise. As recent studies have shown, frontal ablation is most importantly influenced by the sub-surface and surface water temperatures, at the same time interlinked with complex ice-ocean interactions. Since in the last years warm water masses from the West Spitsbergen Current are increasingly affecting the fjords of Western Svalbard, referred to as the process of Atlantification, the relevance to improve our knowledge about water temperature dynamics as well as the interactions with frontal ablation is rising. In this study, the temporal and spatial variations of sub-surface ocean temperatures in three fjord systems in Western Svalbard were investigated by reanalysing data from previous studies. A high variability of water temperatures on a temporal as well as spatial scale were found, reflecting the complex dynamics between different factors, such as fjord bathymetry, ongoing Atlantification, influence from different ocean currents, salinity, mixing of water masses, and tides.

Measurements at different depths are revealing temperature value ranges of up to ± 25% of the annual temperature range for a divergence of 10m in the measurement depth. Profile measurements are therefore strongly recommended for future observations. Tidal variations occur in only one of three fjord system, with temperature variations of up to 2.5°C per day. The analysis of the influence of these warm water peaks, enduring only a few hours, on frontal ablation should be part of future research projects, since the difference to the daily mean water temperature can be up to 1°C. Differences in domination of certain water masses, such as cold or warm waters, can vary strongly in different locations within the fjord system, depending on the interplay of the different impacting factors. Concluding from the results, the depth and location of water temperature measurements, play a key role for making reliable assumptions concerning ice-ocean interactions, since water temperatures can vary strongly with depth and distance from the glacier front.

How to cite: Schulthess, M., Otto, J., Berntell, E., and Zhang, Q.: Temporal and spatial variations of sub-surface ocean temperatures in fjord systems, Western Svalbard, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20778, https://doi.org/10.5194/egusphere-egu2020-20778, 2020

D3881 |
EGU2020-8627
Sandro Dahlke, Nicholas Hughes, Penelope Wagner, Sebastian Gerland, Tomasz Wawrzyniak, Boris Ivanov, and Marion Maturilli

The Svalbard archipelago in the Arctic North Atlantic is experiencing rapid changes in the surface climate and sea ice distribution, with impacts for the coupled climate system and the local society. Using observational data of surface air temperature (SAT) from 1980–2016 across the whole Svalbard archipelago, and sea ice extent (SIE) from operational sea ice charts,  a systematic assessment of climatologies, long-term changes and regional differences is conducted. The proximity to the warm water mass of the West Spitsbergen Current (WSC) drives a markedly warmer climate in the western coastal regions compared to northern and eastern Svalbard. This imprints on the SIE climatology in southern and western Svalbard, where the annual maxima of 50–60% area ice coverage are substantially less than 80–90% in the northern and eastern fjords. Owing to winter-amplified warming, the local climate is shifting towards more maritime conditions, and SIE reductions of between 5% to 20% per decade in particular regions are found, such that a number of fjords in the west have been virtually ice-free in recent winters. The strongest decline comes along with SAT forcing and occurs over the most recent 1–2 decades in all regions. In the 1980s and 1990s, enhanced northerly winds and sea ice drift can explain 30–50% of SIE variability around northern Svalbard, where they had correspondingly lead to a SIE increase. At the same time, interannual temperature fluctuations within the WSC waters can explain 20-37% of SIE variability in a number of fjords on the west coast. With an ongoing warming it is suggested that both the meteorological and cryospheric conditions in eastern Svalbard will become increasingly similar to what is already observed in the western fjords, namely suppressed typical Arctic climate conditions.

How to cite: Dahlke, S., Hughes, N., Wagner, P., Gerland, S., Wawrzyniak, T., Ivanov, B., and Maturilli, M.: The observed recent surface air temperature development across Svalbard and concurring footprints in local sea ice cover, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8627, https://doi.org/10.5194/egusphere-egu2020-8627, 2020

D3882 |
EGU2020-17819
Florina Ardelean, Marinela Chețan, Andrei Dornik, Alexandru Onaca, Goran Georgievski, Dmitry Drozdov, Vladimir Romanovsky, Stefan Hagemann, Dmitry Nicolsky, and Dmitry Sein

Pechora Region, located in North-East European Russia, is a unique natural environment with high biodiversity and wilderness areas, such as coastal habitats, the Arctic tundra or the Ural Mountains. The area lies on different permafrost zones and faces considerable challenges such as the over-exploitation of natural resources or climate change related. Our objective is to analyze landscape changes in the last 30 years using free available satellite data and identify possible influences on the degradation of permafrost in the study area. We used Surface Reflectance images from Landsat archive between 1985 and 2019. For each year, normalized indices were derived, illustrating consistency of green vegetation, as Normalized Difference Vegetation Index (NDVI), and vegetation moisture, Normalized Difference Moisture Index (NDMI). From MODIS data archive we used land surface temperature (LST), between 2000 and 2019. Moreover, the Global Surface Water dataset which contains maps with the spatial and temporal distribution of permanent and seasonal surface water from 1984 to 2018 was used. These data were aggregated to yearly mean (i.e. NDVI, NDMI, LST) or yearly sum (surface water), for the entire Pechora region. The results reveal a significant increase in NDVI mean. This "greening" of the tundra landscape, especially the southern tundra, between 1985 and 2019 has also been highlighted in other studies in the Arctic. Similarly, NDMI shows a slight increase of vegetation moisture in this area in the last three decades. Vegetation dynamics in the last 20 years is in accordance with LST evolution, showing an increase especially in the August mean temperature, more significant after 2011. From the analysis of the spatio-temporal changes of the water surfaces, a significant increase in seasonal water can be observed after 1997, and a relatively stable trend of permanent waters, with minimum values in 1999, 2003 and 2012. In the same time, an increase in the active layer thickness in the last 20 years of measurements in a site located in the study area has been documented. We conclude that Pechora Region experienced significant landscape changes in the last 30 years, our results showed mostly positive changes on vegetation consistency and moisture, and a high spatial variability of surface water.

Acknowledgement

This work is funded for WUT by a grant of the Romanian National Authority for Scientific Research and Innovation, CCDI-UEFISCDI, project number ERANET-RUS-PLUS-SODEEP, within PNCD III in the frame of ERA-Net plus Russia, TSU is supported by MOSC RF # 14.587.21.0048(RFMEFI58718X0048), AWI and HZG are supported by BMBF (Grant no. 01DJ18016A and 01DJ18016B).

How to cite: Ardelean, F., Chețan, M., Dornik, A., Onaca, A., Georgievski, G., Drozdov, D., Romanovsky, V., Hagemann, S., Nicolsky, D., and Sein, D.: Recent landscape changes assessed by remotely sensed data in Pechora Region, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17819, https://doi.org/10.5194/egusphere-egu2020-17819, 2020