Study WP5.7 Ice Sheets and Atmospheric Drivers

Description

This Study is led by Ulrika Willén from SMHI. Additional contributors to this Study are Ruth Mottram and Shuting Yang from DMI.

The main CCI ECVs used in this Study are Land Surface Temperature, Total Column Water Vapour, Cloud, and Snow.

It is estimated that this Study will run from February 2024 until August 2025.

The scientific questions this Study aims to address include:

• Can regional/global climate models represent accurately the atmospheric and surface processes affecting the ice-sheets?
• Do the models capture the variability of the ECV’s and the albedo and emissivity feedbacks over the ice sheets?
• Where, when and why do the surface mass (energy) balance of the models processes perform least and most well?
• Which ECV’s show the most important biases affecting the surface mass budget estimates from regional/global climate models?
• Can the metrics be used for observational based model selection to reduce the spread of the ice sheet contributions to the future sea level rise?

Mottram et al. (2019) showed mass change time series for the entire Greenland Ice Sheet generated by DTU and TUDR and also inter-comparison of mass change from GRACE (Greenland Ice Sheet CCI GMB product) and two regional climate models (HIRHAM5 and RACMO2.3) for different drainage basins and the entire Greenland Ice Sheet. This Study plans to repeat this type of inter-comparison for SMB and for the observed Surface Elevation Changes (SEC) for the whole basin and the sub-basins, comparing the observed variability with the regional models Surface Energy Balance (SEB) and the individual components (SWN, LWN, LE, and H) for Greenland and Antarctica.

Motivation

Atmospheric rivers bring warm and humid air that affect the ice sheets

From Wille et al. (2022): "the most intense atmospheric rivers induce extremes in temperature, surface melt, sea-ice disintegration, or large swells that destabilize the ice sheets with 40% probability. This was observed during the collapses of the Larsen A and B ice shelves during the summers of 1995 and 2002 respectively. Overall 60% of calving events from 2000-2022 were triggered by atmospheric rivers. The loss of the buttering effect from these ice shelves leads to further continental ice loss and subsequent sea level-rise. Under future warming projections the Larsen C ice shelf will be at risk from the same processes."

Clouds drive differences in future surface melt over the Antarctic ice shelves

From Kittel et al. (2021): "Clouds containing a larger amount of supercooled liquid water lead to stronger melt, subsequently favouring the absorption of solar radiation due to the snowmelt–albedo feedback. As liquid-containing clouds are projected to increase the melt spread associated with a given warming rate, they could be a major source of uncertainties in projections of the future Antarctic contribution to sea level rise."

References

• Mottram et al 2019: An Integrated View of Greenland Ice Sheet Mass changes based on Models and Satellite Observations. https://www.mdpi.com/2072-4292/11/12/1407
• Wille et al 2022: Intense atmospheric rivers can weaken ice shelf stability at the Antarctica Peninsula. https://www.nature.com/articles/s43247-022-00422-9
• Kittel et al 2021: Clouds drive differences in future surface melt over the Antarctic ice shelves. https://tc.copernicus.org/articles/16/2655/2022/

Results and conclusions

Results and conclusions will be provided once the Study is complete.