Large and irreversible future decline of the Greenland ice sheet
Large and irreversible future decline of the Greenland ice sheet
复制标题
DOI：
10.5194/tc-14-4299-2020
复制
发表时间：
2020-12-01
期刊：
影响因子：
5.2
通讯作者：
Smith, Robin S.
中科院分区：
文献类型：
--
作者：
Gregory, Jonathan M.;George, Steven E.;Smith, Robin S.
我们已经研究了格陵兰冰盖的演变下的一系列恒定的气候典型的那些预计到本世纪末使用动力冰盖模式（Glimmer）耦合到大气环流模式（FAMOUS冰AGCM）。冰盖表面质量平衡（SMB）的模拟AGCM内的降雪和表面能量通量，包括再冻结和高度的依赖性AGCM网格框内的多层雪计划。数千年来，在任何温暖的气候下，冰盖都会达到一个新的稳定状态，其质量与全球气候变化的幅度相关。如果维持最近观察到的SMB气候，全球平均海平面上升（GMSLR）将达到0.5-2.5 m。对于任何超过3 K的全球变暖，对GMSLR的贡献超过5 m。对于所考虑的最大全球变暖（约+5 K），GMSLR的速率最初为2.7 mm yr（-1），最终只有一个小冰帽持续存在，导致GMSLR超过7 m。我们的分析给出了一个与以前的工作有质的不同的印象，因为我们没有发现一个急剧的阈值变暖，划分的情况下，冰盖遭受的减少很少，其中大部分是失去。最后的稳定状态是通过从海岸撤退在一些地方和增加SMB的趋势，由于增强的云量和降雪量在剩余的冰盖上的地形变化对大气环流的影响，超过了SMB减少的趋势，从表面高度的降低。如果20世纪末的气候在冰盖质量下降到低于相当于海平面4米的阈值后恢复，它将不会再生到目前的程度，因为一旦冰盖从那里撤退，该岛北方的降雪量就会减少。在这种情况下，大约2 m的GMSLR将变得不可逆。为了避免这一结果，必须在冰盖下降到临界质量之前扭转人为气候变化，在政府间气候变化专门委员会第五次评估报告的可能范围内，以最高的质量损失率，大约600年后将达到临界质量。
We have studied the evolution of the Greenland ice sheet under a range of constant climates typical of those projected for the end of the present century using a dynamical ice sheet model (Glimmer) coupled to an atmosphere general circulation model (FAMOUS-ice AGCM). The ice sheet surface mass balance (SMB) is simulated within the AGCM by a multilayer snow scheme from snowfall and surface energy fluxes, including refreezing and dependence on altitude within AGCM grid boxes. Over millennia under any warmer climate, the ice sheet reaches a new steady state, whose mass is correlated with the magnitude of global climate change imposed. If a climate that gives the recently observed SMB were maintained, global-mean sea level rise (GMSLR) would reach 0.5-2.5 m. For any global warming exceeding 3 K, the contribution to GMSLR exceeds 5 m. For the largest global warming considered (about +5 K), the rate of GMSLR is initially 2.7 mm yr(-1), and eventually only a small ice cap endures, resulting in over 7m of GMSLR. Our analysis gives a qualitatively different impression from previous work in that we do not find a sharp threshold warming that divides scenarios in which the ice sheet suffers little reduction from those in which it is mostly lost. The final steady state is achieved by withdrawal from the coast in some places and a tendency for increasing SMB due to enhancement of cloudiness and snowfall over the remaining ice sheet by the effects of topographic change on atmospheric circulation, outweighing the tendency for decreasing SMB from the reduction in surface altitude. If late 20th-century climate is restored after the ice sheet mass has fallen below a threshold of about 4m of sea level equivalent, it will not regrow to its present extent because the snowfall in the northern part of the island is reduced once the ice sheet retreats from there. In that case, about 2m of GMSLR would become irreversible. In order to avoid this outcome, anthropogenic climate change must be reversed before the ice sheet has declined to the threshold mass, which would be reached in about 600 years at the highest rate of mass loss within the likely range of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.