Decreasing sea-ice coverage, increasing permafrost-derived inputs and increasing ice sheet and glacier discharge will continue to affect high latitude environments in the coming decades under all future climate scenarios. Such changes at the interface between the ocean and the cryosphere raise questions about the downstream effects in marine ecosystems, as increased meltwater discharge is likely to impact not only coastal hydrology but also biogeochemistry, sediment transport and ecosystem services such as fisheries and carbon sequestration. However, the impact of increasing melt on fjord and coastal environments is poorly constrained, impacting our ability to make predictions regarding the consequences of future climate change. In order to understand the effect of changing cryosphere-derived inputs on high latitude fjords and marine coastal environments, knowledge concerning the physical and biochemical perturbations occurring in the sea ice and water column and the structure, function and resilience of affected ecosystems must be integrated. In this session we explicitly welcome cross-disciplinary attempts to understand how far reaching the effects of sea-ice, permafrost derived material and glacial changes are on marine biogeochemistry, productivity, biodiversity, and ecosystem services. Topics may include, yet are not limited to, the effect of sea-ice, permafrost, and glacier discharge on sea-ice and water column structure, primary and secondary production, community structure, macronutrient and micronutrient availability, microbial processes, the carbonate system, and the biological carbon pump. Modelling experiments, and studies based on long-term observational records including sediment traps and proxy reconstructions from marine sediment cores are also welcome.

One of the most striking features of global climate change is the strongly amplified response of surface air temperature in the Arctic and the associated strong decline in sea ice. Both observational and climate modeling studies have shown that the Arctic is a region very susceptible to climate change; moreover, changes occurring in the Arctic are likely to have more wide-spread implications. Arctic amplification manifests itself in a number of ways, most notably in the current retreat and thinning of Arctic sea ice. A variety of processes and feedbacks have been proposed that contribute to amplified Arctic warming, most of them associated with sea ice. The most well-known is the surface-albedo feedback, which is associated with retreating sea-ice and snow cover. While most climate models exhibit an Arctic amplification signal with respect to ongoing and future changes, the inter-model range in simulated amplification is large, suggesting that the magnitudes of the various feedbacks contributing to Arctic warming and the role of sea ice therein are still uncertain. This session specifically aims to identify, characterize and quantify the processes and feedbacks that govern amplified Arctic warming and sea ice retreat, and it also addresses the climate impacts on the lower latitudes associated with Arctic changes (for instance the relation between sea ice reductions, heat flux changes and atmospheric circulation changes beyond the Arctic region). We therefore invite contributions on the causes, mechanisms and climate feedbacks associated with Arctic climate change and sea ice decline, and the possible links to weather and climate outside the Arctic. We welcome studies based both on climate model results and/or observational datasets, for near-past, present and future climate changes.

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

This session is linked to the Pan-Eurasian EXperiment (PEEX; www.atm.helsinki.fi/peex), a multi-disciplinary, -scale and -component climate change, air quality, environment and research infrastructure and capacity building programme. It is aimed at resolving major uncertainties in Earth system science and global sustainability issues concerning the Arctic, Northern Eurasia and China regions. This session aims to bring together researchers interested in (i) understanding environmental changes effecting in pristine and industrialized Pan-Eurasian environments (system understanding); (ii) determining relevant environmental, climatic, and other processes in Arctic-boreal regions (process understanding); (iii) the further development of the long-term, continuous and comprehensive ground-based, air/seaborne research infrastructures together with satellite data (observation component); (iv) to develop new datasets and archives of the continuous, comprehensive data flows in a joint manner (data component); (v) to implement validated and harmonized data products in models of appropriate spatio-temporal scales and topical focus (modeling component); (vi) to evaluate impact on society though assessment, scenarios, services, innovations and new technologies (society component).
List of topics:
• Ground-based and satellite observations and datasets for atmospheric composition in Northern Eurasia and China
• Impacts on environment, ecosystems, human health due to atmospheric transport, dispersion, deposition and chemical transformations of air pollutants in Arctic-boreal regions
• New approaches and methods on measurements and modelling in Arctic conditions;
• Improvements in natural and anthropogenic emission inventories for Arctic-boreal regions
• Physical, chemical and biological processes in a northern context
• Aerosol formation-growth, aerosol-cloud-climate interactions, radiative forcing, feedbacks in Arctic, Siberia, China;
• Short lived pollutants and climate forcers, permafrost, forest fires effects
• Carbon dioxide and methane, ecosystem carbon cycle
• Socio-economical changes in Northern Eurasia and China regions.
PEEX session is co-organized with the Digital Belt and Road Program (DBAR), abstracts welcome on topics:
• Big Earth Data approaches on facilitating synergy between DBAR activities & PEEX multi-disciplinary regime
• Understanding and remote connection of last decades changes of environment over High Asia and Arctic regions, both land and ocean.

Several subsystems of the Earth system have been suggested to react abruptly at critical levels of anthropogenic forcing. Well-known examples of such Tipping Elements include the Atlantic Meridional Overturning Circulation, the polar ice sheets and sea ice, tropical and boreal forests, as well as the Asian monsoon systems. Interactions between the different Tipping Elements may either have stabilizing or destabilizing effects on the other subsystems, potentially leading to cascades of abrupt transitions. The critical forcing levels at which abrupt transitions occur have recently been associated with Tipping Points.

It is paramount to determine the critical forcing levels (and the associated uncertainties) beyond which the systems in question will abruptly change their state, with potentially devastating climatic, ecological, and societal impacts. For this purpose, we need to substantially enhance our understanding of the dynamics of the Tipping Elements and their interactions, on the basis of paleoclimatic evidence, present-day observations, and models spanning the entire hierarchy of complexity. Moreover, to be able to mitigate - or prepare for - potential future transitions, early warning signals have to be identified and monitored in both observations and models.

This interdisciplinary session invites contributions that address Tipping Points in the Earth system from the different perspectives of all relevant disciplines, including

- the mathematical theory of abrupt transitions in (random) dynamical systems,
- paleoclimatic studies of past abrupt transitions,
- data-driven and process-based modelling of past and future transitions,
- early-warning signals
- the implications of abrupt transitions for Climate sensitivity and response,
- ecological and societal impacts, as well as
- decision theory in the presence of uncertain Tipping Point estimates

Confirmed invited speaker: Michael Ghil

State of the art climate models are now run for past, present and future climates. This has opened up the opportunity for paleoclimate modelling and data together to inform on future climate changes. To date, most research in this area has been on constraining basic metrics such a climate sensitivity. In addition, and just as importantly for mankind, the Earth's climate is highly variable on all spatial and temporal scales with implications for understanding both the industrial epoch
and future climate projections. These changes in variability (spatial or temporal) can impact the recurrence frequency of extreme events which can have catastrophic effects on society. Yet, it is unclear if a warmer future is one with more or less climate variability, and at which scales. A multitude of feedbacks are involved.

We welcome contributions that improve quantification, understanding and prediction of past, present and future climate and its variability in the Earth System across space and time scales. This includes contributions looking at "steady state" climate features such as climate sensitivity as well as those investigating changes in climate variability and scaling properties. The session is multidisciplinary and brings together studies related to atmospheric science, oceanography, glaciology, paleoclimatology and nonlinear geoscience, to examine the complementarity of ideas and approaches. We particularly encourage submissions that combine models run for the past, present and future with data syntheses to constrain the spread of future predictions, submissions which combine models and data in the past to make strong conclusions or testable hypotheses about the future, as well as work highlighting future experiments and data required to strengthen the link to the future. We welcome contributions using case studies, idealised or realistic modelling, synthesis, and model-data comparison studies that provide insights into past, present and future climate variability on local to global, and synoptic to orbital timescales. Members of the PAGES working group on Climate Variability Across Scales (CVAS) are welcome.

Changes in the Arctic and Antarctic climate systems are strongly related to processes in the boundary layer and their feedbacks with the free troposphere, ocean and ice. An adequate understanding and quantification of these processes is necessary to improve predictions of future changes in the polar regions and their teleconnection with mid-latitude weather and climate, including meridional transport of heat, moisture and chemical constituents. Processes include atmosphere-ocean-ice (AOI) interactions, physical and chemical snow processes (e.g. snow photochemistry), exchange of chemical constituents including biogeochemical impacts , sources of aerosol, polynya formation processes, sea ice production and loss, and cloud formation, which represent key processes for the atmosphere, ocean and the cryosphere. AOI interactions are also triggered by and have feedbacks with synoptic systems and mesoscale weather phenomena such as cold air outbreaks, katabatic winds and polar lows. Associated processes also include the effect of extreme events such as warm air advection and clouds on the surface energy budget and related boundary layer exchanges. In addition, understanding natural processes including AOI interactions is essential to understand of the background atmosphere to quantify the anthropogenic impacts. Shallow inversions, mostly during winter-time, lead to high air pollutant concentrations. Even though severe air pollution episodes are frequently observed in the Arctic, knowledge on urban emission sources, transport and atmospheric chemical processing of pollution, especially under cold and dark conditions, are poorly understood. Similarly, the polar boundary layer can involve complicated radiative processes such as shallow stable layers with fog present. In addition, polar boundary layers can mediate chemical, aerosol, and isotope exchanges between the atmosphere and the firn important to the interpretation of ice core records.
This session is intended to provide an interdisciplinary forum to bring together researchers working in the area of boundary layer processes and high-latitude weather and climate (including snow physics, air/snow chemistry, and oceanography). Cryosphere and atmospheric chemistry processes (the focus of the IGAC/SOLAS activity “CATCH” and the IGAC/IASC activity “PACES”) are highly relevant to this session. We also encourage preliminary results from field programs such as MOSAiC and other high-latitude research efforts.

Clouds play an important role in the polar climate due to their interaction with atmospheric radiation and their role in the hydrological cycle linking poleward water vapour transport with precipitation, thereby affecting the mass balance of the polar ice sheets. Cloud-radiative feedbacks have also an important influence on sea ice. Cloud and precipitation properties depend strongly on the atmospheric dynamics and moisture sources and transport, as well as on aerosol particles, which can act as cloud condensation and ice nuclei.

This session aims at bringing together researchers using observational and/or modeling approaches (at various scales) to improve our understanding of polar tropospheric clouds, precipitation, and related mechanisms and impacts. Contributions are invited on various relevant processes including (but not limited to):


- Drivers of cloud/precipitation microphysics at high latitudes,
- Sources of cloud nuclei both at local and long range,

- Linkages of polar clouds/precipitation to the moisture sources and transport,

- Relationship of the poleward moisture transport to processes in the tropics and extra-tropics, including extreme transport events (e.g., atmospheric rivers, moisture intrusions),

- Relationship of moisture/cloud/precipitation processes to the atmospheric dynamics, ranging from synoptic and meso-scale processes to teleconnections and climate indices,

- Role of the surface-atmosphere interaction in terms of mass, energy, and cloud nuclei particles (evaporation, precipitation, albedo changes, cloud nuclei sources, etc)
- Impacts that the clouds/precipitation in the Polar Regions have on the polar and global climate system, surface mass and energy balance, sea ice and ecosystems.

Papers including new methodologies specific to polar regions are encouraged, such as (i) improving polar cloud/precipitation parameterizations in atmospheric models, moisture transport events detection and attribution methods specifically in the high latitudes, and (ii) advancing observations of polar clouds and precipitation. We would like to emphasize collaborative observational and modeling activities, such as the Year of Polar Prediction (YOPP), Polar-CORDEX, the (AC)3 project on Arctic Amplification, SOCRATES, ACE and other campaigns in the Arctic and Southern Ocean/Antarctica, and encourage related contributions.

The session is endorsed by the SCAR Antarctic Clouds and Aerosols Action Group.


Public information:
Dear Authors,

Thank you all for your great contributions to this session. Hopefully, you have all already successfully uploaded your display material - if not please try to do it on Tuesday (before the Live Chat). If this is not possible - you can do it also during this month. Everyone in any case is welcome to participate in the Live Chat to share their work.

We invite everyone to check the posted material before our session's Live Chat, which is scheduled on 6 May, 08:30–10:15 (CEST=UTC+2). The Live Chat will be open from 8:15 to 10:45 CEST and is only by text chatting.

During the Live Chat we (conveners) will call the authors in the order of the Displays (which will be visible on the right from the chat's window) to shortly introduce their work (motivation.. main points..). It will be easier if everyone has this SHORT text prepared before hand. Please avoid copy/pasting the entire abstract, as all session participants have had the possibility to read the abstract and the posted material prior to the chat session. Then the chat will be open for questions and comments from all participants (we also recommend if possible to prepare your questions beforehand). With 21 abstracts we will have about 5 min to discuss each display.

If there are authors who are certainly not available to be present during the Live Chat - please let us know. You are also welcome to ask your co-authors or colleagues to present your work if the main author is not available at the chat time.

The Chat will be not recorded or stored. Only abstracts and displays will be available after this session. Everyone is welcome to post their comments directly to the Displays (commenting will be open until 1 June). This provides more freedom to discuss.

Looking forward to this new way of science sharing! Hope it goes smoothly:)

Best wishes to you all

Irina, Susanne, Manfred, Tom, Nicole

The polar climate system is strongly affected by interactions between the atmosphere and the cryosphere. Feedback mechanisms between snow, land ice, sea ice and the atmosphere, such as blowing snow, ice melt, polynya formation, and sea ice production play an important role. Atmosphere-ice interactions are also triggered by synoptic weather phenomena such as cold air outbreaks, katabatic winds, polar cyclones, atmospheric rivers, Foehn winds and heatwaves. However, our understanding of these processes is still incomplete, and to fully capture how atmosphere, land ice and sea ice are coupled on different spatial and temporal scales, remains a major challenge.
This session will provide a setting to foster discussion on the atmosphere-ice coupling in both the Northern and Southern Hemispheres. It will offer the opportunity to review newly acquired knowledge, identify gaps, and which instruments, tools, and studies can be designed to address these open questions.
We invite contributions on all observational and modelling aspects of Arctic and Antarctic meteorology and climatology that address atmospheric interactions with the cryosphere. This may include studies of atmospheric dynamics that influence sea-ice dynamics or ice-sheet mass balance, or investigations into the variability of the atmospheric circulation such as polar jets, the circumpolar trough, storm tracks and their link to changes in the cryosphere.

Mountains cover approximately one quarter of the total land surface on the planet, and a significant fraction of the world’s population lives in their vicinity. Orography critically affects weather and climate processes at all scales and, in connection with factors such as land-cover heterogeneity, is responsible for high spatial variability in mountain weather and climate.

Due to this high complexity, monitoring and modeling the atmosphere and the other components of the climate system in mountain regions is challenging both at short (meteorological) and long (climatological) time-scales. This session is devoted to the better understanding of weather and climate processes in mountain and high-elevation areas around the globe, as well as their modification induced by global environmental change.

We welcome contributions describing the influence of mountains on the atmosphere on meteorological time-scales, including terrain-induced airflow, orographic precipitation, land-atmosphere exchange over mountains, forecasting and predictability of mountain weather. Furthermore we invite studies that investigate climate processes and climate change in mountain areas and its impacts on dependent systems, based on monitoring and modeling activities. Particularly welcome are contributions that merge various sources of information and reach across disciplinary borders (atmospheric, hydrological, cryospheric, ecological and social sciences). In this respect the session invites also contributions on outcomes of the WMO "High Mountain Summit" taking place in October 2019.

Public information:
Online survey (including questions about a possible follow-up webinar): https://form.jotformeu.com/83462227858365

In this session, we invite contributions to explore diverse experiences with inter- and transdisciplinary research and practice, that is specifically applied in the mountain context. Taking mountains as complex social-ecological systems, they provide a concrete and spatially-defined contexts in which to explore how global change phenomena manifests and how it poses challenges and opportunities for communities and society in general.

Addressing societal concerns, and finding suitable solutions with regards to associated impacts of global change in mountains, requires and inter- and transdisciplinary (IT-TD) approach to research and practice. We invite contributions based on empirical research and/or practical experience with IT-TD, to critically reflect on these practices in the mountains context and learn from experiences that explicitly address societal grand challenges such as (but not limited to) climate change impacts and adaptation, transformations to sustainability, disaster risk reduction, or transitions to low carbon economies. We welcome contributions depicting research experiences in European mountain regions, other mountain regions around the world, as well as contributions from Early Career Researchers.

The session is led and coordinated by the Mountain Research Initiative (MRI) with expectations to be able to draw from this session as inputs for the formulation of future research agendas and coordination of research collaborations in mountain regions, worldwide.

www.mountainresearchinitiative.org

Public information:
In this session, we invite contributions to explore diverse experiences with inter- and transdisciplinary research and practice, that is specifically applied in the mountain context. Taking mountains as complex social-ecological systems, they provide a concrete and spatially-defined contexts in which to explore how global change phenomena manifests and how it poses challenges and opportunities for communities and society in general.

Addressing societal concerns, and finding suitable solutions with regards to associated impacts of global change in mountains, requires and inter- and transdisciplinary (IT-TD) approach to research and practice. We invite contributions based on empirical research and/or practical experience with IT-TD, to critically reflect on these practices in the mountains context and learn from experiences that explicitly address societal grand challenges such as (but not limited to) climate change impacts and adaptation, transformations to sustainability, disaster risk reduction, or transitions to low carbon economies. We welcome contributions depicting research experiences in European mountain regions, other mountain regions around the world, as well as contributions from Early Career Researchers.

The session is led and coordinated by the Mountain Research Initiative (MRI) with expectations to be able to draw from this session as inputs for the formulation of future research agendas and coordination of research collaborations in mountain regions, worldwide.

www.mountainresearchinitiative.org

Climate change is projected to result in an increase in extreme and compound weather events, which pose a growing threat to human well-being and the achievement of the UN Sustainable Development Goals (SDGs). Further warming is also projected to reduce the efficacy of carbon sinks acting as negative feedbacks on warming and increase the risk of crossing tipping points and triggering cascading changes in the climate and ecosystems. These processes may reduce the Earth system’s resilience, which has the potential to further amplify climate change and extremes and worsen societal impacts.

Maintaining Earth in the Holocene-like conditions that have enabled the development of the world’s societies will require better understanding of feedbacks and tipping dynamics in both the human world and the biophysical Earth. Societies will need to embark on rapid socio-economic and governance transformations in order to both reduce the risk of triggering tipping points and to improve societal resilience to increasingly likely extreme events. Earth resilience brings the complex dynamics and perturbations associated with human activities into Earth system analysis, and increasingly captures socio-economic as well as biophysical dynamics.

In this session we welcome transdisciplinary and cross-scale contributions relating to climate extremes, tipping dynamics, and Earth resilience, covering topics ranging from the cascading impacts of extreme and compound events, key feedbacks and tipping points in both biophysical and human systems, enhancing societal resilience to extreme events, and the potential for rapid social transformations to global sustainability.

Public information:
EGU 2020 Session TS3.2/NH10.7
Climate Extremes, Tipping Dynamics, and Earth Resilience in the Anthropocene
6 May, 14:00-18:00

This session will run as an EGU website hosted text-based chat accessible here, as well as through a simultaneous Zoom video room (link to be provided during the livechat).

Both the EGU chatroom and the Zoom video room will be moderated.
Comments on the presentations can be made at the EGU website at any time, for asynchronous responses.
Comments and questions asked in the EGU chatroom will be forwarded to the Zoom presenters. This means all questions will get responses, but this may not happen within the timeslot of the presentation.
To facilitate real-time dialogue with the presenters, please go to the Zoom session.

When joining the Zoom session remember to mute yourself, and to ask questions please raise your hand (available from the 'participants' button) and unmute when the chair calls on you. If you are a presenter, unmute when called on and share your screen if you have a few slides to show. Each presenter gets 10 minutes max including Q&A, so we suggest presenting some summary slides for a few minutes and then taking questions for the rest.