New estimates for the rise in sea levels due to ice sheet mass loss
under climate change

Date:
September 17, 2020
Source:
Hokkaido University
Summary:
An international consortium of researchers under the aegis of CMIP6
has calculated new estimates for the melting of Earth's ice sheets
due to greenhouse gas emissions and its impact on sea levels,
showing that the ice sheets could together contribute more than
40 cm by the end of 2100.



FULL STORY ==========================================================================
An international consortium of researchers under the aegis of CMIP6 has calculated new estimates for the melting of Earth's ice sheets due to greenhouse gas emissions and its impact on sea levels, showing that the
ice sheets could together contribute more than 40 cm by the end of 2100.


==========================================================================
One of the many effects of global warming is the increase of sea levels
due to the melting and retreat of the ice sheets in the Arctic and the Antarctic. As the sea level rises, large areas of densely populated
coastal land will become uninhabitable. It is vital that we understand
the impact climate change interventions could have on the rate of melting
and, consequently, changes in sea level.

The Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6), consisting
of more than 60 scientists from 36 institutions across the world --
including Dr.

Christopher Chambers and Professor Ralf Greve from the Institute of
Low Temperature Science at Hokkaido University -- has used the latest generation of models to estimate the impact of global warming on ice
sheets. Their results were published in a special issue of the journal
The Cryosphere on September 17.

The ISMIP6 team projected the changes of the Greenland and Antarctic Ice
Sheets (GrIS/AIS) between 2015 and 2100 under global warming conditions predicted by climate modelling. The advantage of ISMIP6 was that it used fourteen different models to estimate the changes in the ice sheet under
two greenhouse gas (GHG) emissions pathways: the pessimistic scenario,
where there is no change in current trends, leading to a rapid increase
in GHG emissions; and the optimistic scenario, where comprehensive steps
are taken to reduce GHG emissions. Using different models to estimate
the changes was vital to this endeavour, as they have different baselines
and assumptions.

Ralf Greve and Christopher Chambers modelled the behavior of ice sheets
using the SICOPOLIS model. The first version was released in 1995 by
Greve, and since then it has been continuously developed and used for
a large number of studies.

The SICOPOLIS model uses data from 1990 as a baseline for the
experiments. As the model has a 25-year history with an uninterrupted development and publication record, it brought a unique perspective
to ISMIP6.

The rate of ice sheet change was modelled under different forcings
provided by climate models: future changes of precipitation, surface
melting over the ice sheets, surface and ocean temperatures. The goal was
to estimate how much the mass loss of the ice sheets would contribute
to the rise in average sea levels beyond what has already been put in
motion. The study found that, by 2100, the GrIS would raise sea levels
by 4-14 cm under the pessimistic scenario, but only 1.5-5 cm under
the optimistic scenario. For the AIS, the results point to a greater
range of possibilities, from ice sheet change that decreases sea level
by 7.8 cm to increasing it by 30 cm under the pessimistic scenario,
and an increase of 0-3 cm under the optimistic scenario.

"Mass change from the AIS is notoriously difficult to predict: Increasing
ocean temperatures erode the bottom of large floating ice shelves,
causing loss; while the AIS can also gain mass by increased snowfall
due to warmer air temperatures. However, we are constantly improving
our understanding of the ice sheets and their interaction with the
Earth's climate system. Modelling intercomparison studies like ISMIP6
are an effective tool to provide society with the necessary information, including uncertainties, for rational decisions," said Ralf Greve.

This effort took over six years of collaboration, and the findings
of ISMIP6 will help inform the Sixth Assessment Report (AR6) of
the Intergovernmental Panel on Climate Change (IPCC), scheduled for
release in 2022. ISMIP6 is part of the sixth phase of the Coupled Model Intercomparison Project (CMIP6). CMIP6 currently has a total of 23
endorsed Model Intercomparison Projects (MIPs), and has been invaluable
in assessing our understanding of climate and climate change.


========================================================================== Story Source: Materials provided by Hokkaido_University. Note: Content
may be edited for style and length.


========================================================================== Journal References:
1. He'le`ne Seroussi, Sophie Nowicki, Antony J. Payne, Heiko Goelzer,
William H. Lipscomb, Ayako Abe-Ouchi, Ce'cile Agosta, Torsten
Albrecht, Xylar Asay-Davis, Alice Barthel, Reinhard Calov,
Richard Cullather, Christophe Dumas, Benjamin K. Galton-Fenzi,
Rupert Gladstone, Nicholas R.

Golledge, Jonathan M. Gregory, Ralf Greve, Tore Hattermann,
Matthew J.

Hoffman, Angelika Humbert, Philippe Huybrechts, Nicolas C. Jourdain,
Thomas Kleiner, Eric Larour, Gunter R. Leguy, Daniel P. Lowry,
Chistopher M. Little, Mathieu Morlighem, Frank Pattyn, Tyler Pelle,
Stephen F.

Price, Aure'lien Quiquet, Ronja Reese, Nicole-Jeanne Schlegel,
Andrew Shepherd, Erika Simon, Robin S. Smith, Fiammetta Straneo,
Sainan Sun, Luke D. Trusel, Jonas Van Breedam, Roderik S. W. van
de Wal, Ricarda Winkelmann, Chen Zhao, Tong Zhang, Thomas
Zwinger. ISMIP6 Antarctica: a multi-model ensemble of the Antarctic
ice sheet evolution over the 21st century. The Cryosphere, 2020;
14 (9): 3033 DOI: 10.5194/tc-14-3033-2020
2. Heiko Goelzer, Sophie Nowicki, Anthony Payne, Eric Larour, Helene
Seroussi, William H. Lipscomb, Jonathan Gregory, Ayako Abe-Ouchi,
Andrew Shepherd, Erika Simon, Ce'cile Agosta, Patrick Alexander,
Andy Aschwanden, Alice Barthel, Reinhard Calov, Christopher
Chambers, Youngmin Choi, Joshua Cuzzone, Christophe Dumas, Tamsin
Edwards, Denis Felikson, Xavier Fettweis, Nicholas R. Golledge,
Ralf Greve, Angelika Humbert, Philippe Huybrechts, Sebastien
Le clec'h, Victoria Lee, Gunter Leguy, Chris Little, Daniel
P. Lowry, Mathieu Morlighem, Isabel Nias, Aurelien Quiquet, Martin
Ru"ckamp, Nicole-Jeanne Schlegel, Donald A. Slater, Robin S. Smith,
Fiamma Straneo, Lev Tarasov, Roderik van de Wal, Michiel van den
Broeke. The future sea-level contribution of the Greenland ice
sheet: a multi-model ensemble study of ISMIP6. The Cryosphere,
2020; 14 (9): 3071 DOI: 10.5194/tc-14-3071-2020 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200917105339.htm

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