第七届青年地学论坛

Melting of the Greenland Ice Sheet (GrIS) is expected to be one of the dominant contributors to the future sea level rise. However, it remains uncertain on how fast and how much will the GrIS contribute to sea level rise. To provide insight on this issue, the evolution of the GrIS from the past into the future is examined using the Parallel Ice Sheet Model (PISM) under the climate forcing prescribed by climate model. Even though we prescribe coldest and warmest climate around 26~ka (kiloyears before present) and 8~ka, the modelled GrIS reaches its maximum and minimum sizes several thousand years later. These results are consistent with reconstructive evidence on the times of both past extremes in climates and the peak ice volumes of the GrIS. It implies that the sea level response of the GrIS lags climate change by several millennia and the evolution of the GrIS does not only controlled by the present climate change, but also affected by the paleo climate. Given that there is a background cooling trend from the Holocene Thermal Maximum (8~ka) towards the Pre-Industrial era, we propose that the GrIS was very likely still experiencing a background growing until the late 20th century when the anthropogenic global warming reverses such natural trend. Our sensitivity simulations indicate that without including this background trend of growing GrIS, the onset and magnitude of sea level contributions from melting GrIS are likely to be overestimated.

大气,海洋,海平面,冰盖