This session explores improvements in our understanding and quantification of past, present and future ice sheet and sea-level changes. We invite contributions about the following topics:

How to improve the reliability of the projections using observations (paleo and present), models and model intercomparison exercises (ISMIP6, and others); assessment of uncertainties and probability distributions of the ice sheets' contribution to sea level change; emerging processes; feedbacks coming from interactions between components (ice sheets, ocean, atmosphere, solid earth). We focus on the present and future (multi-centennial) Greenland and Antarctic ice sheets, but paleo-studies are encouraged if they shed a light on the mentioned topics.

This session is related to both ISMASS (http://www.climate-cryosphere.org/activities/groups/ismass) and ISMIP6 (http://www.climate-cryosphere.org/activities/targeted/ismip6).

Public information:
There will be a chat during our session giving each presenter about 5 min. to answer questions.
The schedule is divided into more ISMASS and ISMIP6 related topics and will follow the following time line (which is fluently adapted if presenters are not present):
14:00 - 14:05 Introduction to the chat
14:05 - 14:10 D2555 Ben Galton-Fenzi - Progress towards coupling ice sheet and ocean models
14:10 - 14:15 D2566 Petra Langebroek - Tipping Points in Antarctic Climate Components (TiPACCs)
14:15 - 14:20 D2572 Nadine Wieters - Modular AWI-CM: An Earth System Model (ESM) prototype using the esm-interface library for a modular ESM coupling approach
14:20 - 14:25 D2558 Jon Bamber - Interpretation and Analysis of Projected Ice Sheet Contributions from a Structured Expert Judgement
14:25 - 14:30 D2557 Andrew Shepherd - Trends and projections in ice sheet mass balance
14:30 - 14:35 D2562 Yijing Lin - Antarctic Ice Sheet mass balance over the past decade from 2005 to 2016
14:35 - 14:40 D2569 Johanna Beckmann - How will the Greenland Ice Sheet develop under Extreme Melt Events?
14:40 - 14:45 D2565 Leo van Kampenhout - A regional atmospheric warming threshold for irreversible Greenland ice sheet mass loss
14:45 - 14:50 D2561 Christiaan van Dalum - Evaluation of a new snow albedo scheme in RACMO2 for the Greenland ice sheet
14:50 - 14:55 D2553 Charlotte Lang - Comparison of the surface mass and energy balance of CESM and MAR forced by CESM over Greenland: present and future
14:55 - 15:00 D2554 Nanna Bjørnholt Karlsson - Basal Melt of the Greenland Ice Sheet: The Invisible Mass Budget Term
15:00 - 15:05 D2551 Heiko Goelzer - The future sea-level contribution of the Greenland ice sheet: a multi-model ensemble study of ISMIP6
15:05 - 15:10 D2560 Tony Payne - Contrasting contributions to future sea level under CMIP5 and CMIP6 scenarios from the Greenland and Antarctic ice sheets
15:10 - 15:15 D2552 Tamsin Edwards - Quantifying uncertainties in the land ice contribution to sea level from ISMIP6 and GlacierMIP
15:15 - 15:20 D2568 Helene Seroussi - ISMIP6 Antarctica: a multi-model ensemble of the Antarctic ice sheet evolution over the 21st century
15:20 - 15:25 D2571 Martin Rückamp - Sensitivity of Greenland ice sheet projections to spatial resolution in higher-order simulations: the AWI contribution to ISMIP6-Greenland using ISSM
15:25 - 15:30 D2573 Thomas Kleiner - ISMIP6 Future Projections for Antarctica performed using the AWI PISM ice sheet model
15:30 - 15:35 D2570 Konstanze Haubner - Changes on Totten glacier dependent on oceanic forcing based on ISMIP6
15:35 - 15:40 D2556 Ronja Reese - The role of history and strength of the oceanic forcing in sea-level projections from Antarctica with the Parallel Ice Sheet Model


note: ISMASS and ISMIP6 homepages have been moved and are now available here:
http://www.climate-cryosphere.org/activities/ismass
http://www.climate-cryosphere.org/mips/ismip6

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.

Public information:
We will allocate five minutes of text-based discussion time to each abstract, as follows:

10:45-10:50 Introduction
10:50-10:55 Eelco Rohling
10:55-11:00 Jim Jordan
11:00-11:05 Javier Blasco
11:05-11:10 Emily Hill
11:10-11:15 Felicity McCormack
11:15-11:20 Gordon Bromley
11:20-11:25 Christian Turney
11:25-11:30 Tyler Pelle
11:30-11:35 Liyun Dai
11:35-11:40 Jun-Young Park
11:40-11:45 Christian Ohneiser
11:45-11:50 Catherine Beltran
11:50-11:55 Johannes Sutter
11:55-12:00 Nicolas Ghilain
12:00-12:05 Torsten Albrecht
12:05-12:10 Nicolas Jourdain
12:10-12:15 Christoph Kittel
12:15-12:20 Caroline van Calcar
12:20-12:25 James O'Neill
12:25-12:30 Thore Kausch

Fifty years of routine in-situ and satellite observations have revealed the progressive deterioration of Antarctica’s most vulnerable regions to climate change: the Antarctic Peninsula and West Antarctic ice sheets. The rapid destabilisation of Larsen A and B ice shelves in the Antarctic Peninsula and the ongoing, potentially irreversible ice losses at Pine Island and Thwaites glaciers, West Antarctica, have been linked to a complex marriage of ocean and atmosphere forcing mechanisms impinging on the continent from the Weddell, Bellingshausen and Amundsen Seas. These phenomena have raised questions about the past and future stability of the ice sheets and water mass properties, and have motivated research focused on elucidating the precise ice-ocean-atmosphere interactions controlling oceanographic and cryospheric change over palaeo- to contemporary timescales. Offshore, similar questions have arisen regarding the role of seabed topography and changing sea ice and oceanographic conditions, and how such phenomena may ultimately impact ice sheet mass-losses.

This session welcomes contributions examining the range of controls driving cryospheric and oceanic change across the Antarctic Peninsula and West Antarctic Ice Sheet regions, as well as those in the wider Weddell Sea sector. Together with model and remotely sensed studies, this session will showcase early results from the International Thwaites Glacier Collaboration and several recent research campaigns conducted in the Weddell Sea.

Rationale: Progressive thawing of permafrost poses a significant threat to the stability of arctic landscapes, and has strong consequences for our climate. To predict the transition of arctic landscapes and its consequence for climate-feedback, we need to understand the dynamics of permafrost thaw. Most climate models assume a gradual, top-down thawing of permafrost, resulting in gradual decomposition of carbon and enhanced plant growth (“Arctic Greening”). However, evidence of an alternative, abrupt thawing trajectory of permafrost (“Arctic Browning”) is currently increasing across the Arctic. Consequences for landscape stability and climate feedback diverge widely between these trajectories, which emphasizes the need to understand their triggers.

Aim: In this session we aim to bring together and integrate the state-of the art on the future development of permafrost ecosystems from various disciplinary backgrounds. Thereby, we hope to improve our understanding of (i) the anticipated occurrence of various thaw phenomena under global warming, (ii) the implications of these various thaw phenomena for permafrost ecosystems and (iii) the implications of various thaw phenomena for climate feedbacks.

We have compiled an exiting programme covering mechanisms, processes and fluxes at different spatial scales, from landscape to microbe. Contributions come from accross all permafrost regions from a wide range of research institutes.

The session will be started of by professor Merritt Turetsky (incoming Director, INSTAAR at the University of Colorado Boulder) on our current knowledge and the main research gaps related to the cross-scale impacts of abrupt thaw phenomena, from local-scale changes that affect water and food security to carbon emissions and global climate. She will also discuss how permafrost thaw is interacting with other disturbance regimes such as wildfire.