Greenland ice sheet may halve in volume by year 3000

Scientists create numerous models to estimate the impact of global warming on the Greenland ice sheet up to the year 3000.

As a result of global warming in the 21st century, the Greenland ice sheet may contribute several metres to sea-level rise in the centuries to come. However, effective climate change mitigation measures will greatly reduce its decay.

One of the many effects of global warming is rising sea levels, to which the melting and retreat of the Earth’s ice sheets and glaciers is a major contributor. As the sea levels continue to rise, large areas of densely populated coastal land could ultimately become uninhabitable without extensive coastal modification. Therefore, it is vital to understand the impact of different pathways of future climate change that caused fluctuations in sea level due to melting ice sheets and glaciers.

Professor Ralf Greve and Dr Christopher Chambers at the Institute of Low Temperature Science, Hokkaido University, simulated the evolution of the Greenland ice sheet up until the year 3000 to investigate the long-term impacts of 21st-century warming.

Their predictions were published in the Journal of Glaciology.

The Ice Sheet Model Intercomparison Project

The Ice Sheet Model Intercomparison Project for the Coupled Model Intercomparison Project, Phase 6 (ISMIP6), was a major international effort that utilised the latest generation of climate models to estimate the impact of global warming on the ice sheets of Antarctica and Greenland.

The objective was to provide input for the recently published Sixth Assessment Report of the IPCC. Based on their contribution to ISMIP6, the research team examined the long-term perspective for the Greenland ice sheet beyond the 21st century, under global-warming conditions.

Greve and Chambers utilised the ice sheet model, SICOPOLIS, to carry out future projections for each of the 12 ISMIP6 experiments for the unabated warming pathway and the two experiments for the reduced emissions pathway, extending the time period to the year 3000. The set-up until the year 2100 was the same as for the original ISMIP6 experiments. After 2100, the climate was assumed to remain the same as at the end of the 21st century, without considering further warming trends.

Greenland ice sheet
Simulated mass loss of the Greenland ice sheet from 1990 until 3000 expressed as sea-level contribution

Unabated warming and reduced emissions pathways

An unequivocal distinction between the responses to the unabated warming and reduced emissions pathways arises. By the year 3000, the unabated warming pathway causes ice loss of 0.71 to 3.54 meters sea-level equivalent (SLE), while for the reduced emissions pathway the loss is only 0.16 to 0.4 meters SLE.

These numbers are much larger than for the 21st century. The melting and retreat of the Greenland ice sheet occurs in all regions from the far North to the South, and it evolves gradually over time. Even though the loss can be as large as 50% of the entire ice volume, it does not develop as a sudden instability.

This study demonstrates clearly that the impact of 21st-century climate change on the Greenland ice sheet extends well beyond the 21st century itself, and the most severe consequences — possibly a multi-meter contribution to sea-level rise — will likely only be seen later in the millennium.

Greenland ice sheet
Comparison of the simulated thickness of the Greenland ice sheet at the beginning (a) and end (b) of one of the simulations for the unabated warming pathway (MIROC5/RCP8.5, ice loss 1.62 meters SLE). The melting and retreat of the Greenland ice sheet occurs in all regions from the far north to the south

For this study, only a single ice-sheet model (SICOPOLIS) was applied, and the results were obtained under the simplifying assumption of the constant late-21st-century climate. In the future, the ISMIP6 community will conduct simulations with more realistic future climate scenarios beyond 2100, encompassing the full range from an ongoing, extended warming to a reduction below 21st-century extremes. Other research groups will contribute results obtained with different ice-sheet models. This will provide a more complete picture of expected long-term mass loss of the Earth’s ice sheets.

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