ITS1.7/GM2 | Sandy solutions for coasts / Arctic coastal processes
EDI

This session is a compilation of two independent sessions: ITS1.7 ‘Sandy solutions for coastal safety, measurements and modelling’ and GM7.3 ‘Arctic coastal processes’.

Future projections show that coastal regions are among the most vulnerable ecosystems on our planet. From nearshore to dunes, the coastal system provides ecosystem services such as water supply and storage, recreation, biodiversity and flood protection, all of which can be considered of critical importance for human well-being. Climate change, sea level rise and anthropogenic impacts can affect these services by altering topography and habitat development. Flexible nature-based solutions have been proposed to promote resilience against climate change and safeguard coastal services for current and future generations. For this session we aim to bring together experts from varying disciplines focused on measuring, modelling and designing nature-based solutions in a changing world. This includes but is not limited to topics related to coastal morphology, sediment and vegetation dynamics, hydrology, and anthropogenic impacts.

Decreasing extent and duration of sea ice cover, changes in storm patterns as well as rising sea surface and air temperatures impact coastal processes in the Arctic. Wave overtopping, flooding and coastal erosion pose risks to societies and infrastructure located at the coast. There is a pressing need to understand the rates and mechanisms of coastal change to better predict future trajectories under the changing climate. In this session, we invite contributions from a range of disciplines and across time scales on local to pan-Arctic studies related to coastal processes in the Arctic. Those can include observational (satellite and instrumental) data, historical data, geological records and proxy data, model simulations as well as forecasts, for the past, present and future rates and drivers of Arctic coastal change. The common denominator of these studies will be their focus on a better understanding of short- to long-term mechanisms and feedbacks that drive Arctic coastal changes, and their impact on coastal communities and infrastructure, at local to global scales.

Co-organized by BG4
Convener: Michel Riksen | Co-conveners: Zuzanna SwiradECSECS, Maria Ansine Jensen, Juul Limpens, Gregor LuetzenburgECSECS, Anna IrrgangECSECS
Orals
| Fri, 28 Apr, 16:15–18:00 (CEST)
 
Room N1
Posters on site
| Attendance Fri, 28 Apr, 14:00–15:45 (CEST)
 
Hall X3
Orals |
Fri, 16:15
Fri, 14:00

Orals: Fri, 28 Apr | Room N1

Chairpersons: Michel Riksen, Zuzanna Swirad, Maria Ansine Jensen
16:15–16:25
|
EGU23-67
|
ITS1.7/GM2
|
ECS
|
On-site presentation
Eva Lansu, Valérie Reijers, Solveig Höfer, Arjen Luijendijk, Max Rietkerk, Martin Wassen, Evert Jan Lammerts, and Tjisse van der Heide

Coastal ecosystems provide vital services, including water storage, carbon sequestration, biodiversity, and coastal protection. Human disturbances, however, cause massive losses. The most direct impact is habitat destruction through infrastructure development, restricting the space available to coastal ecosystems and impeding their capacity to adapt to sea level rise by landward retreat – a phenomenon called ‘coastal squeeze’. While shoreline retreat is intensively studied, coastal congestion through infrastructure remains unquantified. Here we calculated the distance to the nearest human-made structure along 263,900 transects worldwide to show that infrastructure occurs at a 560-meter median distance from the shoreline. Moreover, we find that 18% of global sandy shores harbour less than 100 m of infrastructure-free space, and that 14-17% of the unimpacted space may drown by 2100 according to sea level rise projections. Further analyses show that population density and gross domestic product explain 40-44% of observed squeeze variation, emphasizing the intensifying pressure imposed as countries develop and populations expand. Encouragingly, we find that nature reserves relieve squeezing by 3-5 times, illustrating their effectiveness. Yet, at present only 16% of world’s sandy shores has a protected status. We therefore argue that expansion of nature reserves could be key to preserving coastal resilience to sea level rise.

How to cite: Lansu, E., Reijers, V., Höfer, S., Luijendijk, A., Rietkerk, M., Wassen, M., Lammerts, E. J., and van der Heide, T.: A global analysis of how human infrastructure squeezes sandy coasts, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-67, https://doi.org/10.5194/egusphere-egu23-67, 2023.

16:25–16:35
|
EGU23-1076
|
ITS1.7/GM2
|
ECS
|
On-site presentation
Jan-Markus Homberger, Aaron Lynch, Juul Limpens, and Michel Riksen

Coastal ecosystems are vulnerable to climate change, with rising sea levels and increased anthropogenic pressure constraining space for natural processes. Nature based solutions using sediments rather than hard surfaces in coastal defense may offer an alternative that both creates new habitats and offer a flexible protection against flooding.

In contrast to hard infrastructure, the topography of dunes depends on the highly dynamic processes of wind and waves and the resistance to them offered by dune vegetation. Perennial grass species such as marram grass (Ammophila arenaria) and sand couch (Elytrigia juncea) play a key-role for topographic stability and the development and shape of coastal dune forms. This is usually attributed to their dense cover which effectively traps sand as well as their positive growth response to burial by sediments. Therefore, species like marram grass have been used as ecosystem engineers in both past and recent coastal dune restoration projects.

Whether this solution will be applicable in the future depends on climate change. Coastal vegetation is vulnerable to climate change due to its susceptibility to changes in growing conditions (e.g. Temperature, Precipitation). Especially at the dry-beach section where the influence of groundwater is limited, a change in growing season precipitation could potentially affect the cover of dune grasses. Past research was already able to establish a general link between dune development and growth in function of precipitation. However, to this date direct responses of dune vegetation to precipitation has not been quantified.

We explored the response of dune building grasses to summer precipitation and its implication for the future dune building in a two-step approach. We used a greenhouse-experiment to derive species growth relationships with water availability for marram grass and sand couch. In a second step we used these relationships to explore the impact of potential changes in summer precipitation on the growth of these species. We found that both marram grass and sand couch were equally sensitive to changes in water availability and responded positively to an increase in it. Comparing soil moisture from the field to the greenhouse, showed that field water availability tended to be on the lower end of ranges in the greenhouse. This suggests that dune vegetation in the field is susceptible to drought effects. Exploring these results further using climate scenarios, we found that plant growth was increased by 1.3 % (experimental period) – 1.8 % (extrapolated) under the most recent RCP 4.5 IPCC projection and by 9.6 – 13 % for an extremely wet year. In contrast, for an extremely dry year plant growth could decrease by 6.2 – 8.2 %.

While changes of < 2 % in plant growth might have limited implications for dune development and stability, years of extreme climate conditions show a bigger range in plant growth (- 8 % - + 13 %) which is more likely to also have direct consequences for dune growth and development. Incorporating these relationships between plant growth and climate in models of coastal dune development should improve predictions of climate change impacts.

How to cite: Homberger, J.-M., Lynch, A., Limpens, J., and Riksen, M.: Response of dune-building grasses to summer precipitation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1076, https://doi.org/10.5194/egusphere-egu23-1076, 2023.

16:35–16:45
|
EGU23-2771
|
ITS1.7/GM2
|
ECS
|
On-site presentation
Sasja van Rosmalen, Jan-Markus Homberger, Michel Riksen, and Juul Limpens

Sandy shores serve a multitude of purposes; they protect the inland from flooding, support a high biodiversity, and are recreation hotspots. To what extent these functions can coexist or are mutually exclusive is unclear, especially given increasing stressors such as rising sea levels and urbanization. Knowledge on the trade-offs between these functions is important when designing these areas and nature-based solutions to ensure the desired results. We investigated the effect of recreational pressure on the establishment of two common dune building grass species (Ammophila arenaria and Elytrigia juncea). We conducted a field introduction experiment with seeds and rhizomes of both species along increasing distance to a beach entrance. We established a total of 300 plots, following a randomised block design with 4 factorial treatments (species * type diaspore) and 60 replicates for two beaches on the Dutch barrier Island of Terschelling. Plant material was collected from the wild, using local genetic material. Plant seeds were left in their husk to mimic natural dispersal. Plots were georeferenced by means of Real Time Kinematic and left unmarked to enable undisturbed recreation.  

Recreation pressure was assessed by counting the number of people at different beach sections, confirming that anthropogenic pressure increased with distance to the beach entrance. Establishment success was monitored by counting the number of emerged seeds and sprouted rhizomes per plot at regular intervals across the growing season. To control for drivers other than recreation pressure, we also monitored environmental variables, such as the change in beach level. Preliminary results suggest that environmental factors such as erosion and burial are limiting the establishment success for all treatments. Moreover, a positive effect of distance from the entrance on the establishment success of both species can be observed. This is especially clear within the first 100 meters. The strongest effect seems to be for Ammophila arenaria. These preliminary results indicate that both sediment dynamics and recreational pressure play a role in the new establishment of these species on the upper beach. This means that the impact of both should be considered when designing sandy coastal areas. 

How to cite: van Rosmalen, S., Homberger, J.-M., Riksen, M., and Limpens, J.: Recreation impact on establishment of dune building species, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2771, https://doi.org/10.5194/egusphere-egu23-2771, 2023.

16:45–16:55
|
EGU23-4119
|
ITS1.7/GM2
|
On-site presentation
Glenn Strypsteen and Pieter Rauwoens

In front of the traditional dike at Oosteroever, Belgium, a new 120x20 m² artificial dune with planted marram grass of different densities and patterns was built in January 2021. This man-made dune was constructed to reduce the local aeolian sand nuisance on the dike. The complex interaction between aeolian sand transport and vegetation will ensure future morphological development of a dune body strengthening the local coastal protection. For an optimal design of these planted dunes, a fundamental knowledge of morphological changes is required. This study is twofold: 1) Investigate dune growth by exploring a multi-monthly field dataset of wind characteristics and high-resolution topographic data, 2) Development and assessment of the AeoLiS model for simulation of this new planted coastal dune field. The performance of AeoLiS is analyzed by comparing observed and simulated results of erosion and deposition patterns and cross-shore bed level changes. The total volume of sand in the dune has increased significantly since the plantation of marram grass, resulting in 15 m³ m-1 due to aeolian sand transport from the surrounding beach. Most dune growth occurred during the first year. Dune growth during the second year was less pronounced and was attributed to the influence of supply limitations, vegetation characteristics, and sediment erosion by wind and storm events. The results of the model simulations demonstrate that AeoLiS can replicate the spatial patterns and profile development inside the artificial dune area to some extent. However, to adequately account for the interaction between vegetation and aeolian sand transport, the model's treatment of vegetation dynamics needs to be improved.

How to cite: Strypsteen, G. and Rauwoens, P.: Morphological changes in a planted coastal dune field: measurements and modelling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4119, https://doi.org/10.5194/egusphere-egu23-4119, 2023.

16:55–17:05
|
EGU23-15297
|
ITS1.7/GM2
|
ECS
|
Virtual presentation
Haye Geukes, Alexander Van Oudenhoven, and Peter Van Bodegom

Nature-based solutions (NbS) are fast becoming the norm for multifunctional climate adaptation to the combined challenges of increased sea-level rise, coastal population densities, and erosion of sandy shores worldwide, delivering functions such as flood prevention, recreation, and biodiversity benefits. However, it remains a challenge to the research field to inform decision-makers well on the outcomes and trade-offs of designing, planning, and managing the multifunctional NbS. This study set out to identify the information requirements by decision-makers on NbS for coastal climate adaptation. Using the Sand Motor in The Netherlands as a case study, we applied a policy science framework to distinguish four stages of decision-making to quantitatively analyse the content of functions and indicators utilized per stage in public policy documents. These stages are the ambition, political, bureaucratic, and provisioning processes. This study is the first comprehensive empirical investigation distinguishing these crucial stages of decision-making to analyse NbS information requirements. Our results show, most notably, that as the project developed through the decision-making stages, the content of the functions and indicators changed from abstract to concrete. And, with it, the content of the information required shifted significantly. These results suggest that it is crucial for academic researchers to recognize the decision-making process their information will be used in and adapt its content and level of abstraction accordingly to increase its uptake in decision-making. This study lays the groundwork for future research into the multiple dimensions of NbS decision-making and for the increased understanding of the information requirements on evaluation and trade-offs in planning, designing, and managing NbS, to increase the ability of NbS to deliver multifunctional coastal climate adaptation for sandy shores worldwide.

How to cite: Geukes, H., Van Oudenhoven, A., and Van Bodegom, P.: Decision-Making on Nature-Based Solutions for Multifunctional Coastal Climate Adaptation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15297, https://doi.org/10.5194/egusphere-egu23-15297, 2023.

17:05–17:10
17:10–17:20
|
EGU23-1493
|
ITS1.7/GM2
|
Highlight
|
On-site presentation
Brian Moorman, Andrew Clark, and Dustin Whalen

Around the Arctic Ocean there are many stretches of coastline composed of ice-rich sediments. With the dramatic climatic, oceanic and terrestrial changes that are currently underway, there is considerable concern over the stability of these coasts and how they impact coastal communities. Unfortunately, there is still relatively little research that has been done the processes at work in these environments. Being able to effectively model coastal erosion in a permafrost setting is highly desirable. With the complexity that ice-rich permafrost conditions add to the coastal setting, modelling erosion involves a more detailed understanding of the physical and thermal conditions as well as the sedimentological and wave action processes. This research examines the rate and character of coastal erosion of ice-rich terrain and role that re-sedimentation has on the shallow water energy balance in preserving sub-bottom massive ice. It also addresses it implications to secondary sea bottom disturbance as the water depth increases.

The study area was Peninsula Point which is approximately 10 km west of Tuktoyaktuk, Northwest Territories, Canada. The massive ice and retrogressive thaw flows at this location are some of the more dramatic examples of the impact of ice-rich permafrost on coastal processes in the Arctic. Through a three decade long program of remote sensing, geophysical and ground-based monitoring, long-term changes were investigated. The character of coastal retreat above, and below, the waterline in an area where a massive ice body extends to depths below sea level were revealed. Airphoto, satellite imagery and drone data revealed the complexity of erosion with the retreating headwall of retrogressive thaw flow more rapidly eroding the landscape than the observed lateral changes of the waterline. Ground-penetrating radar (GPR) imaged the top and base of the massive ice body as well as providing a delineation of the subsurface sedimentary architecture. In winter, the GPR was pulled behind a snowmobile along transects on land, across the shoreline and out onto the near shore area of the Beaufort Sea. This provided the stratigraphic continuity between the terrestrial and sub-sea settings. The roles of erosion, re-sedimentation and shallow-water thermodynamics in the degradation and preservation of massive ground ice were revealed. The results of this study demonstrate how coastal erosion is much more complex that just the inland movement of the waterline.

How to cite: Moorman, B., Clark, A., and Whalen, D.: Ice-rich permafrost coastline erosion processes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1493, https://doi.org/10.5194/egusphere-egu23-1493, 2023.

17:20–17:30
|
EGU23-11651
|
ITS1.7/GM2
|
ECS
|
On-site presentation
|
Tua Nylén, Carlos Gonzales-Inca, and Mikel Calle Navarro

The Arctic coast is facing rapid, irreversible changes mainly caused by Climate Warming, e.g., melting sea ice, permafrost thaw, glacial retreat, land uplift and sea level rise. These processes are leading to fundamental changes in the ecosystem structure and functioning, negatively impacting biological and human communities. Under this complex setting, more knowledge is needed to identify the hotspots of shoreline displacement at an Arctic scale. Thus, the goal of this study was to develop and describe a procedure for mapping long-term shoreline displacement in the Arctic that can provide local communities and environmental managers better opportunities to adapt to further coastal changes. Therefore, the procedure will need to be transferrable to diverse environments and able to handle pan-Arctic analyses at a 30-meter spatial resolution. In this study, the procedure was developed using two test areas: Tanafjorden in the low Arctic mainland Norway and Kongsfjorden in the high Arctic Svalbard. The presentation introduces the final procedure and validation results, and discusses its applicability to pan-Arctic shoreline displacement analyses.

The procedure was calibrated in the surroundings of Tanafjorden. It was built on a 40-year time-series of open Landsat and Sentinel multispectral satellite images, taken during the Arctic summer. Supervised random forest classification was used to identify land and water pixels, utilizing information from multiple infrared bands and spectral indices. Mountain shadow pixels were treated as their own class and then merged to the land class. Open spatial data were used for limiting the area-of-interest and for automated creation of training data. In total over 700 individual images were first classified separately to account for local environmental conditions and transient illumination conditions. Images were then summarized over 5-year time-steps. The classification results were examined against an independent validation dataset of 2000 land cover observations and manually digitized shoreline, and the supervised classification results were compared to single-band classifications based on Otsu’s thresholding. The final procedure was then validated in the Kongsfjorden environment. The process was built on Google Earth Engine’s image collections and cloud computing infrastructure to minimize computing times.

The results indicate that it is possible to transform open satellite imagery into 40-year pan-Arctic shoreline displacement information, with a 30-meter resolution and an overall accuracy of more than 95 %. Data fusion is needed in most processing steps: to limit the area-of-interest, save computing power and reduce errors, provide information that complements multispectral satellite data and reduce the impact of short-term atmospheric and water-level effects. Summarizing dozens of images efficiently removes data gaps and the impact of noise, but this efficiency is sensitive to the number of summarized images. The single-image classification approach is flexible and seems to make the procedure transferable to different locations. Cloud image collections are needed to remove the bottleneck of reading and writing satellite data, and potentially allows the promising procedure to be applied at a pan-Arctic scale in the future.

How to cite: Nylén, T., Gonzales-Inca, C., and Calle Navarro, M.: Procedure for examining long-term Arctic shoreline displacement from multispectral satellite data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11651, https://doi.org/10.5194/egusphere-egu23-11651, 2023.

17:30–17:40
|
EGU23-14578
|
ITS1.7/GM2
|
ECS
|
Highlight
|
On-site presentation
Rodrigue Tanguy, Annett Bartsch, Barbara Widhalm, Clemens von Baeckmann, Aleksandra Efimova, and Goncalo Vieira

Rapid and unprecedented warming of high latitudes exposes Arctic coastal communities to greater vulnerability as they observe their territory changing through general permafrost degradation, episodes of flooding and accelerated coastal erosion threatening their infrastructure and livelihood. Local information is known for infrastructures mapping and coastal changes but consistency in the measurement is lacking as well as spatial coverage for large coastal areas. The need of a consistent circumpolar dataset is primordial in order to map risks and mitigate impacts for arctic coastal communities. Machine learning methods with Sentinel 1/2 imagery allow the circumpolar mapping of arctic coastal settlements (Bartsch et al. 2021a). Validation of recent updates are supported by high-resolution data from the Pleiades satellites, aerial and drone imagery. 

This study is part of the ESA EO4PAC project which aims to provide a range of satellite derived information, including coastal erosion/accretion and infrastructure in the proximity, for the next generation of the Arctic Coastal Dynamic Database (ACD; Lantuit, et al. 2012).  Previous results highlight the detection of 50% more human presence information than in OpenStreetMap especially in Russia with recent expansion of infrastructures related to expanding oil and gas industry. Recent updates of the SACHI dataset (Bartsch et al. 2021b) will be presented including additional attributes for roads and their validation. A preliminary categorization of settlements with respect to permafrost degradation (based on Permafrost_cci records) and coastal erosion based on the current ACD will be presented.

Bartsch, A., G. Pointner, I. Nitze, A. Efimova, D. Jakober, S. Ley, E. Högström, G. Grosse, P. Schweitzer (2021a): Expanding infrastructure and growing anthropogenic impacts along Arctic coasts. Environmental Research Letters. https://doi.org/10.1088/1748-9326/ac3176

Bartsch, Annett, Pointner, Georg, & Nitze, Ingmar. (2021b). Sentinel-1/2 derived Arctic Coastal Human Impact dataset (SACHI) (Version 1) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.4925911

Lantuit, Hugues; Overduin, Pier Paul; Couture, Nicole; Wetterich, Sebastian; Are, Felix; Atkinson, David; Brown, Jerry; Cherkashov, Georgy A; Drozdov, Dimitry S; Forbes, Donald Lawrence; Graves-Gaylord, Allison; Grigoriev, Mikhail N; Hubberten, Hans-Wolfgang; Jordan, James; Jorgenson, M Torre; Ødegård, Rune Strand; Ogorodov, Stanislav; Pollard, Wayne H; Rachold, Volker; Sedenko, Sergey; Solomon, Steve; Steenhuisen, Frits; Streletskaya, Irina; Vasiliev, Alexander (2012): The Arctic Coastal Dynamics Database: A New Classification Scheme and Statistics on Arctic Permafrost Coastlines. Estuaries and Coasts, 35(2), 383-400, https://doi.org/10.1007/s12237-010-9362-6

How to cite: Tanguy, R., Bartsch, A., Widhalm, B., von Baeckmann, C., Efimova, A., and Vieira, G.: Pan-Arctic remotely sensed observation of coastal settlements - recent updates, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14578, https://doi.org/10.5194/egusphere-egu23-14578, 2023.

17:40–17:50
|
EGU23-12412
|
ITS1.7/GM2
|
ECS
|
On-site presentation
|
Jan Kavan and Mateusz Strzelecki

The consequences of accelerating climatic warming on Arctic landscape evolution are far-reaching. In Svalbard, glaciers are rapidly retreating after the Little Ice Age, which leads to exposing new coastal landscapes from marine-terminating glaciers. Precise quantification of these changes was limited until the complete dataset of Svalbard glacier outlines from 1930’s was made available. Here, we analyse the new Svalbard glacier change inventory data and demonstrate that glacier retreat was responsible for a major shift from marine-terminating towards land-terminating glaciers in the last century. This retreat also led to the formation of 922.9 km of new coastline since 1930’s (representing increase of 16.37% in coastline length) creating pristine landscapes governed by paraglacial processes and sediment-rich nearshore fjord environments. Recent palaeogeographical reconstructions suggest that such a mode of coastal evolution was dominant over the extended periods of the Holocene. Transitions from marine-terminating to land-based glaciers had significant implications for fjord circulation, biological production, state of marine ecosystems, biogeochemical cycles between land and seas, and CO2 budget in coastal waters. Still ongoing climate warming with associated further glacier retreat may lead to more coasts to be exposed in the future. Moreover, glacier retreat will likely cause collapse of Hornbreen-Hambergbreen glacier bridge leading to separation of Sørkappland and rest of Spitsbergen with severe consequences for regional ocean circulation and climate dynamics.

New bays, new straits, new peninsulas and new islands, that have appeared in the last decades of unprecedented warming and associated decay of marine-terminating glaciers in the Arctic are predominantely uncharted and unexplored territories which foreshadow ice-free Arctic and other cold regions of the warmer future. The importance of transdisciplinary research exploring those deglaciated oases has never been more important than at present.

Acknowledgement: The research leading to these results has received funding from the Norwegian Financial Mechanism  2014-2021: SVELTA - Svalbard Delta Systems Under Warming Climate (UMO-2020/37/K/ST10/02852) based at the University of Wroclaw.

How to cite: Kavan, J. and Strzelecki, M.: Glacier decay boosts formation of new Arctic coastal environments – lessons learned from Svalbard, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12412, https://doi.org/10.5194/egusphere-egu23-12412, 2023.