This session will focus on variability in the ocean and its role in the wider climate system using both observations and models. Areas to be considered will include both ocean heat uptake and circulation variability as well as exploring the use of sustained ocean observing efforts and models to make progress in understanding the ocean’s role in the climate system. More than 90% of the excess heat in the climate system has been stored in the ocean, which mitigates the rate of surface warming. Better understanding of ocean ventilation mechanisms, as well as the uptake, transport, and storage of oceanic heat are therefore essential for reducing the uncertainties on global warming projections. Circulation variability and connectivity, particularly from the South Atlantic to the North Atlantic and Arctic Ocean, are also of interest as well as how they are driven by local-, large- or global-scale processes or teleconnections. Sustained observations at sea are being made within a wide variety of programmes and are leading to significant advances in our ability to understand and model climate. Thus, this session will also explore ongoing and planned sustained ocean observing efforts and illuminate their roles in improving understanding of the ocean’s role in the climate system. For example, air-sea flux moorings are being maintained at select sites to assess models and air-sea flux fields. Deep temperature and salinity measurements are being made at time series moorings and will be made by deep Argo floats. Significant advances are also being made using Argo floats for biogeochemistry and carbon measurements. Such observations provide the means to develop linkages between sustained ocean observing and climate modelling. In conclusion, the session will consider key aspects of ocean variability and its climate relevance, as well as encouraging the use of observations and models to enhance understanding of these areas.

The ocean surface mixed layer mediates the transfer of heat, freshwater, momentum and trace gases between atmosphere, sea ice and ocean, thus playing a central role in the dynamics of our climate. This session will focus on the surface mixed layer globally, from the coastal ocean to the deep ocean. We will review recent progress in understanding the key dynamical and biogeochemical processes taking place in the mixed layer: surface waves, Langmuir circulations and turbulence, shear-induced mixing, internal waves, coherent structures, fronts, frontal instabilities, entrainment and detrainment at the mixed layer base, convection, restratification, dynamics of the euphotic layer, carbon and nutrient cycling, etc. The improvement of the representation of surface mixed layer processes in numerical models is a complex and pressing issue: this session will bring together new advances in the representation of mixed layer processes in high resolution numerical models, as well as evaluation of mixed layer properties in climate models using most recent observational datasets. The coupling of the ocean and atmospheric boundary layers as well as the special processes occurring under sea ice and in the marginal sea ice zone will be given special consideration. This session welcomes all contributions related to the study of the oceanic mixed layer independent of the time- and space scales considered. This includes small scale process studies, short-term forecasting of the mixed layer characteristics for operational needs, studies on the variability of the mixed layer from sub-seasonal to multi annual time scales and mixed layer response to external forcing. The use of multiple approaches (coupled numerical modeling, reanalyses, observations) is encouraged.

Ocean ventilation is a process by which water properties imprinted by the atmosphere onto the upper ocean, such as oxygen, carbon dioxide and trace gases, are transported into the ocean interior. In mediating the exchange between the atmosphere and the ocean, ventilation plays an important role in both climate variability and biogeochemical cycles. This is manifested, for example, through the supply of oxygen to the ocean interior, transport and sequestration of nutrients, and the uptake and storage of anthropogenic carbon and heat in the ocean interior. Increased stratification - caused by the warming on the upper ocean under climate change - could lead to a reduction of ocean ventilation over the coming decades. However, the mechanism by which the changes in ocean ventilation will emerge, and their consequences for climate feedback, biogeochemical processes, and ocean ecosystems are not well known.

Developing our understanding of ocean ventilation is inhibited by the wide range of spatial scales inherent in the process, from small-scale mixing to basin scale. Robust projection of future change requires deeper insight into the processes driving ventilation, the spatial and temporal variability of ventilation, and the consequences and impacts of ventilation changes.

We invite contributions that advance understanding on the broad topic of ocean ventilation, its potential to change in a warming climate, and the consequences therein. We seek contributions that investigate both the physical processes involved in ocean ventilation — from small-scale mixing, to mesoscale stirring, to basin scale subduction — as well as the consequences for biogeochemical cycles and marine ecosystems. We welcome contributions from process-oriented studies as well as those that assess and quantify variability and projected changes, and welcome studies making use of observations, theory and/or numerical model.

The session is expected to be in a hybrid format, partly taking place in Vienna in a traditional format, and partly online.

Theoretical and model studies show that the ocean is a chaotic system which spontaneously generates a strong, multi-scale intrinsic chaotic variability: uncertainties in ocean model initial states may grow and strongly affect the simulated variability up to multi-decadal and basin scales, with or without coupling to the atmosphere. In addition, ocean simulations require both the use of subgrid-scale parameterizations that crudely mimic unresolved processes, and the calibration of the parameters associated with these parameterizations. In this context of multiple uncertainties, oceanographers are increasingly adopting ensemble simulation strategies, probabilistic analysis methods, and developing stochastic parameterizations for modeling and understanding ocean variability.

Presentations are solicited about the conception and analysis of ocean ensemble simulations, the characterization of ocean model uncertainties, and the development of stochastic parameterizations for ocean models. The session will also cover the dynamics and structure of chaotic ocean variability, its relationship with atmospheric variability, and the use of dynamical system or information theories for the investigation of oceanic variability. We welcome as well studies about the propagation of chaotic ocean variability towards other components of the climate system, about its consequences regarding ocean predictability, operational forecasts, detection and attribution of climate signals, climate simulations and projections.

The rapid decline of the Arctic sea ice in the last decade is a dramatic indicator of climate change. The Arctic sea ice cover is now thinner, weaker and drifts faster. Freak heatwaves are common. On land, the permafrost is dramatically thawing, glaciers are disappearing, and forest fires are raging. The ocean is also changing: the volume of freshwater stored in the Arctic has increased as have the inputs of coastal runoff from Siberia and Greenland and the exchanges with the Atlantic and Pacific Oceans. As the global surface temperature rises, the Arctic Ocean is speculated to become seasonally ice-free by the mid 21st century, which prompts us to revisit our perceptions of the Arctic system as a whole. What could the Arctic Ocean look like in the future? How are the present changes in the Arctic going to affect and be affected by the lower latitudes? What aspects of the changing Arctic should observational, remote sensing and modelling programmes address in priority?

In this session, we invite contributions from a variety of studies on the recent past, present and future Arctic. We encourage submissions examining interactions between the ocean, atmosphere and sea ice, on emerging mechanisms and feedbacks in the Arctic and on how the Arctic influences the global ocean. Submissions taking a cross-disciplinary, system approach and focussing on emerging cryospheric, oceanic and biogeochemical processes and their links with land are particularly welcome.

The session supports the actions of the United Nations Decade of Ocean Science for Sustainable Development (2021-2030) towards addressing challenges for sustainable development in the Arctic and its diverse regions. We aim to promote discussions on the future plans for Arctic Ocean modelling and measurement strategies, and encourages submissions on the results from IPCC CMIP and the recent observational programs, such as the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC). This session is cosponsored by the CLIVAR /CliC Northern Ocean Regional Panel (NORP) that aims to facilitate progress and identify scientific opportunities in (sub)Arctic ocean-sea-ice-atmosphere research.

Drs Karen Assmann and Wilken-Jon von Appen are the solicited speakers for the session. Karen Assmann will be presenting on physical and ecological implications of Arctic Atlantification. Wilken-Jon von Appen will be talking about eddies in the Arctic Ocean.

The North Atlantic exhibits a high level of natural variability from interannual to centennial time scales, making it difficult to extract trends from observational time series. Climate models, however, predict major changes in this region, which in turn will influence sea level and climate, especially in western Europe and North America. In the last years, several observational projects have been focused on the Atlantic circulation changes, for instance ACSIS, RACE, RAPID, OSNAP, and OVIDE. Another important issue is the interaction between the atmosphere and the ocean as well as the cryosphere with the ocean, and how this affects the climate.

We welcome contributions from observers and modelers on the following topics:

-- climate relevant processes in the North Atlantic region in the atmosphere, ocean, and cryosphere
-- response of the atmosphere to changes in the North Atlantic
-- atmosphere - ocean coupling in the North Atlantic realm on time scales from years to centuries (observations, theory and coupled GCMs)
-- interpretation of observed variability in the atmosphere and the ocean in the North Atlantic sector
-- comparison of observed and simulated climate variability in the North Atlantic sector and Europe
-- dynamics of the Atlantic meridional overturning circulation
-- variability in the ocean and the atmosphere in the North Atlantic sector on a broad range of time scales
-- changes in adjacent seas related to changes in the North Atlantic
-- role of water mass transformation and circulation changes on anthropogenic carbon and other parameters
-- linkage between the observational records and proxies from the recent past

Observations and model simulations illustrate significant ocean variability and associated air-sea interactions in the tropical Atlantic basin from daily-to-decadal time scales. This session is devoted to the understanding of ocean dynamics in the tropical and subtropical Atlantic Ocean, its interaction with the overlying atmosphere from the equator to the mid-latitudes and its climate impacts on adjacent to remote areas. Relevant processes in the ocean include upper and deep ocean circulation, eddies, tropical instability waves, warm pools, cold tongues and eastern boundary upwellings. We are interested in air-sea interactions related to both the seasonal cycle and the development of modes of variability from local to basin scale (e.g. the Meridional Mode, the Atlantic Niño, and the Benguela Niño). We welcome studies on wind variations related to the development of these modes, as well as studies on high-frequency events, such as marine heat waves, the Madden-Julian Oscillation, tropical cyclones and convective systems. Furthermore, we seek studies on climate change in the region, and also of the climatic impacts of change and variability on marine ecosystems. Finally, we are also interested in contributions examining the causes and impacts of systematic model errors in simulating the local to regional Atlantic climate. Studies based on direct observations, reanalysis, reconstructions as well as model simulations are welcome.

The Indian Ocean is unique among the other tropical ocean basins due to the seasonal reversal of monsoon winds and concurrent ocean currents, lack of steady easterlies that result in a relatively deep thermocline along the equator, low-latitude connection to the neighboring Pacific and a lack of northward heat export due to the Asian continent. These characteristics shape the Indian Ocean’s air-sea interactions, variability, as well as its impacts and predictability in tropical and extratropical regions on (intra)seasonal, interannual, and decadal timescales. They also make the basin particularly vulnerable to anthropogenic climate change, as well as related extreme weather and climate events, and their impacts for surrounding regions, which are home to a third of the global population. Advances have recently been made in our understanding of the Indian Ocean’s circulation, interactions with adjacent ocean basins, and its role in regional and global climate. Nonetheless, significant gaps remain in understanding, observing, modeling, and predicting Indian Ocean variability and change across a range of timescales.

This session invites contributions based on observations, modelling, theory, and palaeo proxy reconstructions in the Indian Ocean that focus on recent observed and projected changes in Indian Ocean physical and biogeochemical properties and their impacts on ecological processes, diversity in Indian Ocean modes of variability (e.g., Indian Ocean Dipole, Indian Ocean Basin Mode, Madden-Julian Oscillation) and their impact on predictions, interactions and exchanges between the Indian Ocean and other ocean basins, as well as links between Indian Ocean variability and monsoon systems across a range of timescales. In particular, we encourage submissions on weather and climate extremes in the Indian Ocean, including marine heatwaves and their ecological impacts. We also welcome contributions that address research on the Indian Ocean grand challenges highlighted in the recent IndOOS Decadal Review, and as formulated by the Climate and Ocean: Variability, Predictability, and Change (CLIVAR), the Sustained Indian Ocean Biogeochemistry and Ecosystem Research (SIBER), the International Indian Ocean Expedition 2 (IIOE-2), findings informed by the Coupled Model Intercomparison Project version 6 (CMIP6) on past, present and future variability and change in the Indian Ocean climate system, and contributions making use of novel methodologies such as machine learning.

The Southern Ocean around the latitudes of the Antarctic Circumpolar Current is vital to our understanding of the climate system. It is a key region for vertical and lateral exchanges of heat, carbon, and nutrients, with significant past and potential future global climate implications. The role of the Southern Ocean as a dominant player in heat and carbon exchanges in present and future climate conditions remains uncertain. Indeed, the lack of observations of this system and its inherent sensitivity to small-scale physical processes, not fully represented in current Earth system models, result in large climate projection uncertainties. To address these knowledge gaps, the Southern Ocean has been the subject of recent observational, theoretical, and numerical modelling investigations. These efforts are providing deeper insight into the three-dimensional patterns of Southern Ocean change on sub-annual, multi-decadal and millennial timescales. In this session, we will discuss the current state of knowledge and novel findings concerning the role of the Southern Ocean in past, present, and future climates. These include (but are not limited to) small-scale physics and mixing, water mass transformation, gyre-scale processes, nutrient and carbon cycling, ocean productivity, climate-carbon feedbacks, and ocean-ice-atmosphere interactions. We will also discuss how changes in Southern Ocean heat and carbon transport affect lower latitudes and global climate more generally.

The interaction between the ocean and the cryosphere in the Southern Ocean has become a major focus in climate research. Antarctic climate change has captured public attention, which has spawned a number of research questions, such as: Is Antarctic sea ice becoming more vulnerable in a changing climate? Where and when will melting of ice shelves by warm ocean waters yield a tipping point in Antarctic climate? What role do ice-related processes play in nutrient upwelling on the continental shelf and in triggering carbon export to deep waters? Recent advances in observational technology, data coverage, and modeling provide scientists with a better understanding of the mechanisms involving ice-ocean interactions in the far South. Processes on the Antarctic continental shelf have been identified as missing links between the cryosphere, the global atmosphere and the deep open ocean that need to be captured in large-scale and global model simulations.

This session calls for studies on physical and biogeochemical interactions between ice shelves, sea ice and the ocean. The ice-covered Southern Ocean and its role in the greater Antarctic climate system are of major interest. This includes work on all scales, from local to basin-scale to circumpolar. Studies based on in-situ observations and remote sensing as well as regional to global models are welcome. We particularly invite cross-disciplinary topics involving physical and biological oceanography, glaciology or biogeochemistry.

The Open Session on atmosphere, land and ocean monitoring aims at presenting highlights of recent results obtained through observations and modelling as well as relevant reviews in these fields.
We shall connect with Earth Observations programmes at ESA, EU and worldwide, using new satellites and oberving platforms, as well as new techniques for distributing, merging and analysing EO data using AI.

The session is intended as an open forum for interdisciplinary discussion between representatives of different fields. Thus, we welcome especially overarching presentations which may be interesting to a wider community.

Observations are one major link to get an overall picture of processes within the Earth environment during measurement campaigns. This includes application to derive atmospheric parameters, surface properties of vegetation, soil and minerals and dissolved or suspended matter in inland water and the ocean. Ground based systems and data sets from ships, aircraft and satellites are key information sources to complement the overall view. All of these systems have their pros and cons, but a comprehensive view of the observed system is generally best obtained by means of a combination of all of them.

The validation of operational satellite systems and applications is a topic that has come increasingly into focus with the European Copernicus program in recent years. The development of smaller state-of-the-art instruments, the combination of more and more complex sets of instruments simultaneously on one platform, with improved accuracy and high data acquisition speed together with high accuracy navigation and inertial measurements enables more complex campaign strategies even on smaller aircraft or unmanned aerial vehicles (UAV).

This session will bring together a multidisciplinary research community to present:

• Atmosphere-land-ocean (or inland water) system modelling and validation
• new instruments (Lidar, etc), platforms (UAV etc.), setups and use in multidisciplinary approaches
• Larger scale in-situ and remote sensing observation networks from various platforms (ground based, airborne, ship-borne, satellite)
• recent field campaigns and their outcomes
• (multi-) aircraft campaigns
• satellite calibration/validation campaigns
• sophisticated instrument setups and observations
• advanced instrument developments
• UAV applications

The largest single source of uncertainty in projections of future global sea level is associated with the mass balance of the Antarctic Ice Sheet (AIS). In the short-term, it cannot be stated with certainty whether the mass balance of the AIS is positive or negative; in the long-term, the possibility exists that melting of the coastal shelves around Antarctica will lead to an irreversible commitment to ongoing sea level rise. Observational and paleoclimate studies can help to reduce this uncertainty, constraining the parameterizations of physical processes within ice sheet models and allowing for improved projections of future global sea level rise. This session welcomes presentations covering all aspects of observation, paleoclimate reconstruction and modeling of the AIS. Presentations that focus on the mass balance of the AIS and its contribution towards changes in global sea level are particularly encouraged.

In recent decades, the climate in the polar regions has undergone dramatic changes. Quantifying the individual contributions of Earth system components (cryosphere, ocean, atmosphere, and land) to the observed changes is challenging due to feedback between the components. Examples include (but are not limited to) ice shelf-ocean interactions (through basal melting and cavity geometry evolution) and elevation feedbacks (through surface mass balance). Hence, studies based on individual components of the Earth System have limited capacity to represent all relevant processes. This session aims to provide a platform for sharing coupled modelling experiences incorporating the cryosphere in the polar regions.

Before obtaining scientific outcomes, design decisions must be made in the development of coupled models. Adopting existing coupling technologies or implementing new, concurrent or sequential parallelism, bringing component source codes together or maintaining independence, choosing the level of temporal synchronicity between components operating on different timescales, are all examples of choices to be made.
We solicit both technical and scientific contributions from modelling studies in which feedback and emergent properties between the cryosphere and other Earth System components in polar regions are investigated, better understood, and possibly even quantified. In addition to application of coupled modelling to real world domains, contributions are also invited from idealised studies and intercomparisons, such as the Marine Ice Sheet-Ocean Intercomparison Project (MISOMIP).

Machine learning, artificial intelligence and big data approaches have recently emerged as key tools in understanding the cryosphere. These approaches are being increasingly applied to answer long standing questions in cryospheric science, including those relating to remote sensing, forecasting, and improving process understanding across Antarctic, Arctic and Alpine regions. In doing so, data science and AI techniques are being used to gain insight into system complexity, analyse data on unprecedented temporal and spatial scales, and explore much wider parameter spaces than were previously possible.
In this session we invite submissions that utilise data science and/or AI techniques that address research questions relating to glaciology, sea ice, permafrost and/or polar climate science. Approaches used may include (but are not limited to) machine learning, artificial intelligence, big data processing/automation techniques, advanced statistics, and innovative software/computing solutions. These could be applied to any (or combinations) of data sources including remote sensing, numerical model output and field/lab observations. We particularly invite contributions that apply techniques and approaches that reveal new insights into cryospheric research problems that would not otherwise be achievable using traditional methods, and those that discuss how or if approaches can be applied or adapted to other areas of cryospheric science. Given the rapid development of this field by a diverse group of international researchers, we convene this session to help foster future collaboration amongst session contributors, attendees, and international stakeholders and help address the most challenging questions in cryospheric science.

Ice sheets play an active role in the climate system by amplifying, pacing, and potentially driving global climate change over a wide range of time scales. The impact of interactions between ice sheets and climate include changes in atmospheric and ocean temperatures and circulation, global biogeochemical cycles, the global hydrological cycle, vegetation, sea level, and land-surface albedo, which in turn cause additional feedbacks in the climate system. This session will present data and modelling results that examine ice sheet interactions with other components of the climate system over several time scales. Among other topics, issues to be addressed in this session include ice sheet-climate interactions from glacial-interglacial to millennial and centennial time scales, the role of ice sheets in Cenozoic global cooling and the mid-Pleistocene transition, reconstructions of past ice sheets and sea level, the current and future evolution of the ice sheets, and the role of ice sheets in abrupt climate change.

Ice shelves and tidewater glaciers are sensitive elements of the climate system. Sandwiched between atmosphere and ocean, they are vulnerable to changes in either. The recent disintegration of ice shelves such as Larsen B and Wilkins on the Antarctic Peninsula, current thinning of the ice shelves in the Amundsen Sea sector of West Antarctica, and the recent accelerations of many of Greenland's tidewater glaciers provide evidence of the rapidity with which those systems can respond. Changes in marine-terminating outlets appear to be intimately linked with acceleration and thinning of the ice sheets inland of the grounding line, with immediate consequences for global sea level. Studies of the dynamics and structure of the ice sheets' marine termini and their interactions with atmosphere and ocean are the key to improving our understanding of their response to climate forcing and of their buttressing role for ice streams. The main themes of this session are the dynamics of ice shelves and tidewater glaciers and their interaction with the ocean, atmosphere and the inland ice, including grounding line dynamics. The session includes studies on related processes such as calving, ice fracture, rifting and mass balance, as well as theoretical descriptions of mechanical and thermodynamic processes. We seek contributions both from numerical modelling of ice shelves and tidewater glaciers, including their oceanic and atmospheric environments, and from observational studies of those systems, including glaciological and oceanographic field measurements, as well as remote sensing and laboratory studies.

One of the big challenges in Earth system science consists in providing reliable climate predictions on sub-seasonal, seasonal, decadal and longer timescales. The resulting data have the potential to be translated into climate information leading to a better assessment of global and regional climate-related risks.
The latest developments and progress in climate forecasting on subseasonal-to-decadal and longer timescales will be discussed and evaluated. This will include presentations and discussions of predictions for the different time horizons from dynamical ensemble and statistical/empirical forecast systems, as well as the aspects required for their application: forecast quality assessment, multi-model combination, bias adjustment, downscaling, exploration of artificial-intelligence methods, etc.
Following the new WCRP strategic plan for 2019-2029, prediction enhancements are solicited from contributions embracing climate forecasting from an Earth system science perspective. This includes the study of coupled processes between atmosphere, land, ocean, and sea-ice components, as well as the impacts of coupling and feedbacks in physical, chemical, biological, and human dimensions. Contributions are also sought on initialization methods that optimally use observations from different Earth system components, on assessing and mitigating the impacts of model errors on skill, and on ensemble methods.
We also encourage contributions on the use of climate predictions for climate impact assessment, demonstrations of end-user value for climate risk applications and climate-change adaptation and the development of early warning systems.
A special focus will be put on the use of operational climate predictions (C3S, NMME, S2S), results from the CMIP5-CMIP6 decadal prediction experiments, and climate-prediction research and application projects.
An increasingly important aspect for climate forecast's applications is the use of most appropriate downscaling methods, based on dynamical or statistical approaches or their combination, that are needed to generate time series and fields with an appropriate spatial or temporal resolution. This is extensively considered in the session, which therefore brings together scientists from all geoscientific disciplines working on the prediction and application problems.

To address societal concerns over rising sea level and extreme events, understanding the contributions behind these changes is key to predict potential impacts of sea level change on coastal communities and global economy, and is recognized as one of the Grand Challenges of our time by the World Climate Research Programme (WCRP). To continue this discussion, we welcome contributions from the international sea level community that improve our knowledge of the past and present changes in global and regional sea level, extreme events, and flooding, and produce improved predictions of their future changes.

We welcome studies on various drivers of sea level change and linkages between variability in sea level, heat and freshwater content, ocean dynamics, land subsidence from natural versus anthropogenic influences, and mass exchange between the land and the ocean associated with ice sheet and glacier mass loss and changes in the terrestrial water storage. Studies focusing on future sea level changes are also encouraged, as well as those discussing potential short-, medium-, and long-term impacts on coastal and deltaic environments, as well as the global oceans.

ENSO and its interactions with other tropical basins are the dominant source of interannual climate variability in the tropics and across the globe. Understanding the dynamics, predictability, and impacts of ENSO and tropical basins interactions, and anticipating their future changes are thus of vital importance for society. This session invites contributions regarding all aspects of ENSO and tropical basins interactions, including: dynamics, multi-scale interactions; low frequency, decadal and paleo variability; theoretical approaches; ENSO diversity; global teleconnections; impacts on climate, society and ecosystems; seasonal forecasting and climate change projections of ENSO and its tropical basins interactions. Studies aimed at evaluating and improving model simulations of ENSO, the tropical mean state and the tropical basins interactions basin are especially welcomed.

This session aims to place recently observed climate change in a long-term perspective by highlighting the importance of paleoclimate research spanning the past 2000 years. We invite presentations that provide insights into past climate variability, over decadal to millennial timescales, from different paleoclimate archives (ice cores, marine sediments, terrestrial records, historical archives and more). In particular, we are focussing on quantitative temperature and hydroclimate reconstructions, and reconstructions of large-scale modes of climate variability from local to global scales. This session also encourages presentations on the attribution of past climate variability to external drivers or internal climate processes, data syntheses, model-data comparison exercises, proxy system modelling, and novel approaches to producing multi-proxy climate field reconstructions.

Predictions of climate from seasonal to decadal timescales and their applications are discussed in this session. With a time horizon from a few months up to thirty years, such predictions are of major importance to society, and improving them presents an interesting scientific challenge. This session aims to embrace advances in our understanding of the origins of seasonal to decadal predictability, as well as in improving the respective forecast skill and making the most of this information by developing and evaluating new applications and climate services.

The session covers dynamical as well as statistical predictions (including machine learning methods) and their combination. It investigates predictions of various climate phenomena, including extremes, from global to regional scales, and from seasonal to multi-decadal timescales ("seamless predictions"). Physical processes relevant to long-term predictability sources (e.g. ocean, cryosphere, or land) as well as predicting large-scale atmospheric circulation anomalies associated to teleconnections are discussed, as are observational and emergent constraints on climate variability and predictability. Also, the time-dependence of the predictive skill, or windows of opportunity (hindcast period), are investigated. Analysis of predictions in a multi-model framework, and ensemble forecast initialization and generation, including innovative ensemble approaches to minimize initialization shocks, are another focus of the session. The session pays particular attention to innovative methods of quality assessment and verification of climate predictions, including extreme-weather frequencies, post-processing of climate hindcasts and forecasts, and quantification and interpretation of model uncertainty. We particularly invite contributions presenting the use of seasonal-to-decadal predictions for risk assessment, adaptation and further applications.

In 2015, the UN Sustainable Development Goals and the Paris Agreement on climate recognized the deteriorating resilience of the Earth system, with planetary-scale human impacts constituting a new geological epoch: the Anthropocene. Earth system resilience critically depends on the nonlinear interplay of positive and negative feedbacks of biophysical and increasingly also socio-economic processes. These include dynamics and interactions between the carbon cycle, the atmosphere, oceans, large-scale ecosystems, and the cryosphere, as well as the dynamics and perturbations associated with human activities.

With rising anthropogenic pressures, there is an increasing risk we might be hitting the ceiling of some of the self-regulating feedbacks of the Earth System, and cross tipping points which could trigger large-scale and partly irreversible impacts on the environment, and impact the livelihood of millions of people. Potential domino effects or tipping cascades could arise due to the interactions between these tipping elements and lead to a further decline of Earth resilience. At the same time, there is growing evidence supporting the potential of positive (social) tipping points that could propel rapid decarbonization and transformative change towards global sustainability.

In this session we invite contributions on all topics relating to tipping points in the Earth system, positive (social) tipping, as well as their interaction and domino effects. We are particularly interested in various methodological approaches, from Earth system modelling to conceptual modelling and data analysis of nonlinearities, tipping points and abrupt shifts in the Earth system.

An increasing number of single model large ensemble simulations from Global Climate Models (GCM), Earth System Models (ESM), or Regional Climate Models (RCM) have been generated over recent years, to investigate internal variability and forced changes of the climate system — and to aid the interpretation of the observational record by providing a range of historical climate trajectories that could have been. The increased availability of large ensembles also enables new and inter-disciplinary applications beyond large-scale climate dynamics.

This session invites studies using large GCM, ESM, or RCM ensembles looking at the following topics: 1) Reinterpretation of the observed record in light of internal variability; 2) forced changes in internal variability; 3) development of new approaches to attribute and study observed events or trends; 4) impacts of natural climate variability; 5) assessment of extreme and compound event occurrence; 6) combining single model large ensembles with CMIP archives for robust decision making; 7) large ensembles as testbeds for method development.

We welcome research across all components of the Earth system. Examples include topics ranging from climate dynamics, hydrology and biogeochemistry to research on the role of internal variability in impact studies, focused for example on agriculture, air pollution or energy generation and consumption. We particularly invite studies that apply novel methods or cross-disciplinary approaches to leverage the potential of large ensembles.

Modelling past climate states, and the transient evolution of Earth’s climate remains challenging. Time periods such as the Paleocene, Eocene, Pliocene, the Last Interglacial, the Last Glacial Maximum or the mid-Holocene span across a vast range of climate conditions. At times, these lie far outside the bounds of the historical period that most models are designed and tuned to reproduce. However, our ability to predict future climate conditions and potential pathways to them is dependent on our models' abilities to reproduce just such phenomena. Thus, our climatic and environmental history is ideally suited to thoroughly test and evaluate models against data, so they may be better able to simulate the present and make future climate projections.

We invite papers on palaeoclimate-specific model development, model simulations and model-data comparison studies. Simulations may be targeted to address specific questions or follow specified protocols (as in the Paleoclimate Modelling Intercomparison Project – PMIP or the Deep Time Model Intercomparison Project – DeepMIP). They may include anything between time-slice equilibrium experiments to long transient climate simulations (e.g. transient simulations covering the entire glacial cycle as per the goal of the PalMod project) with timescales of processes ranging from synoptic scales to glacial cycles and beyond. Comparisons may include past, historical as well as future simulations and focus on comparisons of mean states, gradients, circulation or modes of variability using reconstructions of temperature, precipitation, vegetation or tracer species (e.g. δ18O, δD or Pa/Th).

Evaluations of results from the latest phase of PMIP4-CMIP6 are particularly encouraged. However, we also solicit comparisons of different models (comprehensive GCMs, isotope-enabled models, EMICs and/or conceptual models) between different periods, or between models and data, including an analysis of the underlying mechanisms as well as contributions introducing novel model or experimental setups.

The dynamics of the Earth system and its components is highly nonlinear. In particular, several subsystems 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 multidisciplinary 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

Analysis of the energy transfers between and within climate components has been at the core of many step changes in the understanding of the climate system. Large-scale atmospheric circulation, hydrological cycle and heat/moisture transports are tightly intertwined through radiative and heat energy absorption and transports that are sensitive to multiple forcings and feedbacks. Cross-equatorial energy exchanges by the ocean and atmosphere couple Hadley Circulation and Atlantic Overturning circulation, modulating the location and intensity of the ITCZ and the amount of precipitation in monsoon regions. In the extra-tropics, Rossby waves affect the distribution of precipitation and eddy activity, shaping the meridional heat transport from the low latitudes towards the Poles through intermittent events of persistent and co-located blockings and the occurrence of extreme heat waves or cold outbreaks. In the ocean, understanding of energy transfers from large-scale circulation to the internal wave field, through mesoscale and submesoscale eddies, is the basis for the development of new parameterizations and significant modelling advances.
We invite submissions addressing the interplay between Earth’s energy exchanges and the general circulation using modeling, theory, and observations. We encourage contributions on the forced response and natural variability of the general circulation, understanding present-day climate and past and future changes, and impacts of global features and change on regional climate.

Arctic sea ice and high latitude atmosphere and oceans have experienced significant changes over the modern observational era. The polar climate is crucial for the Earth’s energy and water budget, and its variability and change have direct socio-economic and ecological impacts. Thus, understanding high-latitude variability and improving predictions of high latitude climate is highly important for society. Long-term variability in ocean and sea ice are the largest sources for predictability in high latitudes. Dynamical model predictions are not yet in the position to provide us with highly accurate predictions of the polar climate. Main reasons for this are the lack of observations in high latitudes, insufficient initialization methods and shortcomings of climate models in representing some of the important climate processes in high latitudes.

This session aims for a better understanding and better representation of the mechanisms that control high latitude variability and predictability of climate in both hemispheres from sub-seasonal to multi-decadal time-scales in past, recent and future climates. Further, the session aims to discuss ongoing efforts to improve climate predictions at high latitudes at various time scales (e.g., usage of additional observations for initialization, improved initialization methods, impact of higher resolution, improved parameterizations, novel verification approaches) and potential teleconnections of high latitude climate with lower latitude climate. We also aim to link polar climate variability and predictions to potential ecological and socio-economic impacts and encourage submissions on this topic.

The session offers the possibility to present results from ongoing projects and research efforts on the topic of high-latitude climate variability and prediction, including, but not limited to, the WMO Year of Polar Prediction (YOPP), NordForsk-project ARCPATH, MOSAiC, and the H2020-projects APPLICATE, INTAROS, BlueAction, and KEPLER.

This session has greatly benefited by the expansion via added contributions from the CL4.11 session on "Arctic climate change: governing mechanisms and global implications" that 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.

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, including productivity. The processes and feedbacks involved operate on all time scales and it require a range of types of information to understand the processes, drivers and feedbacks involved in Arctic changes, as well as the land-ocean-cryosphere interaction. In this session, we invite contributions from a range of disciplines and across time scales, including observational (satellite and instrumental) data, historical data, geological archives and 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.

Climate change (CC) and ocean degradation (OD) are among the greatest threats to humanity. Climate impacts the ocean in massive ways; the ocean is the climate’s most powerful regulator. Separately or combined, they impact every living being and ecological niche, with poorer communities suffering disproportionately. In turn, flora and fauna (incl humans) are suffering. CC and OD are affecting the cryosphere, biodiversity, and food and water security. Given that humans are the prime cause of this devastating change taking us beyond our planetary boundaries, geoethical issues come to the fore.

The 2020 EGU Declaration of the Significance of Geoscience highlights the need for massive and widespread action to help people around the world to become literate about the changes affecting their and their offsprings’ and communities’ lives. The more people are literate about these changes, the more they can make informed decisions, adapt and mitigate. Previous General Assemblies have addressed climate change literacy (CL). Ocean literacy (OL) has developed strongly in recent years, especially with impetus from the UN Ocean Decade. Ocean-climate literacy (OCL) is an imperative that needs to be addressed massively and urgently, both within and beyond the EGU.

We invite colleagues to submit contributions on any aspects of OCL; this can, of course, include CL (without the ocean) and OL (without the climate). We welcome papers related, eg, to learning processes/experiences, instructional materials, curricular innovation, learning games, citizen initiatives, Ocean Decade activities, evaluation, well-used methods, novel approaches and policies, eg, 1. make OCL an essential component in all subjects and at all levels of education; 2. require all people in positions of responsibility (eg, mayors, teachers, doctors, CEOs, ministers, et al) to pass exams on the basics of climate and/or ocean before taking office. Of particular interest are literacy actions that bring in geoethical dimensions. (If your paper is primarily on geoethics, then a better home is the EGU session on geoethics.) The broad aims of such OCL might include encouraging an intergenerational outlook, developing a sense of the geoethical dimensions of OCL, understanding complexities and implementing solutions.

This session is an opportunity for ECSs, scientists, educators, policy influencers, learning resource developers and other practitioners to share their experience, expertise and research on CL and OL.

The ocean floor hosts a tremendous variety of forms that reflect the action of a range of tectonic, sedimentary, oceanographic and biological processes at multiple spatio-temporal scales. Many such processes are hazards to coastal populations and offshore installations, and their understanding constitutes a key objective of national and international research programmes and IODP expeditions. High quality bathymetry, especially when combined with sub-seafloor and/or seabed measurements, provides an exciting opportunity to integrate the approaches of geomorphology and geophysics, and to extend quantitative geomorphology offshore. 3D seismic reflection data has also given birth to the discipline of seismic geomorphology, which has provided a 4D perspective to continental margin evolution.

This interdisciplinary session aims to examine the causes and consequences of geomorphic processes shaping underwater landscapes, including submarine erosion and depositional processes, submarine landslides and canyons, sediment transfer and deformation, volcanic activity, fluid migration and escape, faulting and folding, and other processes acting at the seafloor. The general goal of the session is to bring together researchers who characterise the shape of past and present seafloor features, seek to understand the sub-surface and surface processes at work and their impacts, or use bathymetry and/or 3D seismic data as a model input. Contributions to this session can include work from any depth or physiographic region, e.g. oceanic plateaus, abyssal hills, mid-ocean ridges, accretionary wedges, and continental margins (from continental shelves to abyss plains). Datasets of any scale, from satellite-predicted depth to ultra high-resolution swath bathymetry, sub-surface imaging and sampling, are anticipated.

This session is organised by the IAG Submarine Geomorphology Working Group.

Contributions are invited on innovative observational, theoretical and modelling studies concerning physical processes in coastal and shelf seas. Processes can include hydrodynamics (e.g., waves, tides, river plumes, currents and Stokes drift, upwelling, eddies, density structures), transport of material (e.g., sediments, contaminants, litter, nutrients), and morphodynamics and sea-bed structure (e.g., evolution of bed forms, banks, Holocene-Antropogene strata or basin shape). Study areas are envisaged between the base of the shelf break and the seaward limit of the surf zone, including tidal basins. However, contributions on processes outside these geographical limits will be considered where they significantly influence processes within these limits. Equally, contributions on climate dynamics, biogeochemistry, and man-made structures will be considered where they significantly influence, or are significantly influenced by, the processes aimed at in this session. Special attention will be given to interactions between physics, biology and biogeochemistry and to global to local scaling of processes, their relative importance, and the representation of these transitions in models.

Oceanographic processes at coastal scales present important differences about deep water oceanography, which result in higher prediction errors for the land-ocean border. In shallow water coastal domains, the bottom topography exerts a strong control on wave/current/turbulence fields and additional factors need to be accounted for. These factors include stratification, land boundary conditions and the interaction with coastal infrastructure. Moreover, the strong non-linear interactions (breaking waves, nearshore circulation), the choice of numerical strategy (nested meshes, finite-elements) or the modulations in restricted domains (suspended sediment clouds, vegetation filtering) may also play a critical role in the predictive quality. Coastal observations are therefore necessary to drive and calibrate numerical models, combining in-situ data and satellite images. The advent of new satellite capabilities (resolution and sensors like for instance those of the Sentinel constellation) and new modelling advances (new couplings, unstructured grids) together with enhanced Coastal Observatories are leading to a qualitative advance of coastal oceanography. The introduction of Artificial Intelligence, Machine Deep Learning and Big Data techniques can speed up these advances and facilitate applications.
These issues become more relevant in a framework of changing climate, since coastal/transitional areas are more strongly impacted by climate (changing domains due to sea-level rise, impulsive river discharges). Because of these reasons, it is timely to discuss recent advances in: a) coastal coupled hydro-morpho-eco modelling; b) aggregation of in-situ/satellite/numerical data from different sources; c) knowledge-based coastal applications; d) ethical constraints to face large uncertainties. Building upon these challenges, we invite presentations on coastal modelling and coupling, local and boundary condition assimilation or operational coastal predictions with/out infrastructure interactions. Contributions exploring the potential and currently open issues of Artificial Intelligence and Big Data techniques for coastal applications are also welcome. These and related coastal topics should conform a fruitful session for discussing applications of coastal science to conventional and nature-based interventions under climate change. Please state if you would be interested in submitting your presentation as a full paper to a peer reviewed special issue in a Q1 journal.

The Mediterranean and Black Seas have recently shown clear signs of climate change, including an increase in sea surface temperature for boths basins, salinization of the intermediate and deep waters and a rise in sea level over the last century for the Mediterranean seas and deoxygenation trends for the Black Sea. These trends stress the vulnerability of these environments given their particularities as semi enclosed densely populated basins.

Urgent social and economic drivers need targeted improvements in weather, cl