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Despite considerable advances in process understanding, numerical modeling, and the observational record of ice sheet contributions to global mean sea-level rise (SLR) since the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change, severe limitations remain in the predictive capability of ice sheet models. As a consequence, the potential contributions of ice sheets remain the largest source of uncertainty in projecting future SLR. Here, we report the findings of a structured expert judgement study, using unique techniques for modeling correlations between inter- and intra-ice sheet processes and their tail dependences. We find that since the AR5, expert uncertainty has grown, in particular because of uncertain ice dynamic effects. For a +2 °C temperature scenario consistent with the Paris Agreement, we obtain a median estimate of a 26 cm SLR contribution by 2100, with a 95th percentile value of 81 cm. For a +5 °C temperature scenario more consistent with unchecked emissions growth, the corresponding values are 51 and 178 cm, respectively. Inclusion of thermal expansion and glacier contributions results in a global total SLR estimate that exceeds 2 m at the 95th percentile. Our findings support the use of scenarios of 21st century global total SLR exceeding 2 m for planning purposes. Beyond 2100, uncertainty and projected SLR increase rapidly. The 95th percentile ice sheet contribution by 2200, for the +5 °C scenario, is 7.5 m as a result of instabilities coming into play in both West and East Antarctica. Introducing process correlations and tail dependences increases estimates by roughly 15%.
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Antarctic geothermal heat flow and its implications for tectonics and ice sheets
Geothermal heat flow (GHF) is an elusive physical property, yet it can reveal past and present plate tectonic processes. In Antarctica, GHF has further consequences in predicting the response of ice sheets to climate change. In this Review, we discuss variations in Antarctic GHF models based on geophysical methods and draw insights into tectonics and GHF model usage for ice sheet modelling. The inferred GHF at continental scale for West Antarctica (up to 119 mW m−2, 95th percentile) points to numerous contributing influences, including non- steady state neotectonic processes. Combined influences cause especially high values in the vicinity of the Thwaites Glacier, a location critical for the accurate prediction of accelerated loss of Antarctic ice mass. The inferred variations across East Antarctica are more subtle (up to 66 mW m−2, 95th percentile), where slightly elevated values in some locations correspond to the influence of thinned lithosphere and tectonic units with concentrations of heat- producing elements. Fine- scale anomalies owing to heat- producing elements and horizontal components of heat flow are important for regional modelling. GHF maps comprising central values with these fine- scale anomalies captured within uncertainty bounds can thus enable improved ensemble- based ice sheet model predictions of Antarctic ice loss.
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- Award ID(s):
- 1917176
- PAR ID:
- 10615966
- Publisher / Repository:
- Nature Publications
- Date Published:
- Journal Name:
- Nature Reviews Earth & Environment
- Volume:
- 3
- Issue:
- 12
- ISSN:
- 2662-138X
- Page Range / eLocation ID:
- 814 to 831
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1038/s43017-022-00348-y
