16:45 〜 17:00
[MIS03-06] Simulating the evolution of the Antarctic ice sheet until the year 2300 with a climate-index method
キーワード：Antarctica, Ice sheet, Antarctic ice sheet, Climate change, Sea-level rise, Modelling
As part of the Coupled Model Intercomparison Project Phase 6 (CMIP6), the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) was devised to assess the likely sea-level-rise contribution from the Antarctic and Greenland ice sheets until the year 2100. ISMIP6 used future climate scenarios as forcings for ice-sheet models developed by several international groups. Results obtained for the Antarctic ice sheet are described by Seroussi+ (2020, Cryosphere, doi: 10.5194/tc-14-3033-2020) and Payne+ (2021, GRL, doi: 10.1029/2020GL091741). Recently, Chambers+ (2021, JoG, doi: 10.1017/jog.2021.124) extended the ISMIP6-Antarctica simulations with SICOPOLIS until the year 3000, using the original ISMIP6 climate forcings until 2100, while assuming a sustained late-21st-century climate without any further trend beyond that.
Here, we construct an ensemble of climate forcings for Antarctica until the year 2300, using results from a MIROC4m RCP8.5 simulation. In the first step, we derive a set of atmospheric and oceanic climate indices from this simulation such that 1995–2014 averages are mapped to zero and 2091–2100 averages to unity. Specifically, for the atmosphere, we construct climate indices for the surface temperature, precipitation, evaporation and surface runoff, and the oceanic climate index reflects the ocean temperature at intermediate depths. In the second step, we use the climate indices to extrapolate the ensemble of ISMIP6 forcings (anomalies relative to 1995–2014, for 2015–2100) to the period 2101–2300. Together with the original ISMIP6 forcings, this method provides smooth climate forcings for the entire period 2015–2300.
We use these forcings to run simulations for the Antarctic ice sheet with SICOPOLIS. Results are shown in Figure 1. For the control run with a constant, 1995–2014 average climate, the ice sheet is stable until the year 2300. For RCP8.5/SSP5-8.5, it suffers a severe mass loss, which amounts to ~1.5 m SLE (sea-level equivalent) for the fourteen-experiment mean, and ~3.3 m SLE for the most sensitive experiment. Most of this loss originates from West Antarctica. For RCP2.6/SSP1-2.6, the loss is limited to a three-experiment mean of ~0.16 m SLE. These numbers are approximately two times larger than what was found by Chambers+ (2021) for the year 2300, thus demonstrating the impact of extended climate change beyond the 21st century.
Here, we construct an ensemble of climate forcings for Antarctica until the year 2300, using results from a MIROC4m RCP8.5 simulation. In the first step, we derive a set of atmospheric and oceanic climate indices from this simulation such that 1995–2014 averages are mapped to zero and 2091–2100 averages to unity. Specifically, for the atmosphere, we construct climate indices for the surface temperature, precipitation, evaporation and surface runoff, and the oceanic climate index reflects the ocean temperature at intermediate depths. In the second step, we use the climate indices to extrapolate the ensemble of ISMIP6 forcings (anomalies relative to 1995–2014, for 2015–2100) to the period 2101–2300. Together with the original ISMIP6 forcings, this method provides smooth climate forcings for the entire period 2015–2300.
We use these forcings to run simulations for the Antarctic ice sheet with SICOPOLIS. Results are shown in Figure 1. For the control run with a constant, 1995–2014 average climate, the ice sheet is stable until the year 2300. For RCP8.5/SSP5-8.5, it suffers a severe mass loss, which amounts to ~1.5 m SLE (sea-level equivalent) for the fourteen-experiment mean, and ~3.3 m SLE for the most sensitive experiment. Most of this loss originates from West Antarctica. For RCP2.6/SSP1-2.6, the loss is limited to a three-experiment mean of ~0.16 m SLE. These numbers are approximately two times larger than what was found by Chambers+ (2021) for the year 2300, thus demonstrating the impact of extended climate change beyond the 21st century.