The Processes-Based Attributes of Four Major Surface Melting Events over the Antarctic Ross Ice Shelf

Abstract

The Ross-Amundsen sector is experiencing an accelerating warming trend and a more intensive advective influx of marine air streams. As a result, massive surface melting events of the ice shelf are occurring more frequently, which puts the West Antarctica Ice Sheet at greater risk of degradation. This study shows the connection between surface melting and the prominent intrusion of warm and humid air flows from lower latitudes. By applying the Climate Feedback-Response Analysis Method (CFRAM), the temporal surge of the downward longwave (LW) fluxes over the surface of the Ross Ice Shelf (RIS) and adjacent regions are identified for four historically massive RIS surface melting events. The melting events are decomposed to identify which physical mechanisms are the main contributors. We found that intrusions of warm and humid airflow from lower latitudes are conducive to warm air temperature and water vapor anomalies, as well as cloud development. These changes exert a combined impact on the abnormal enhancement of the downward LW surface radiative fluxes, significantly contributing to surface warming and the resultant massive melting of ice.

摘要

罗斯冰架-阿蒙森海海域不断增强的变暖趋势,伴随来自海洋的更为强烈的暖湿平流入侵,导致大规模冰架表面融化事件的发生频率升高,西南极洲冰盖面临着更大的退化风险。本文利用气候反馈-响应分析方法,定量分析了来自低纬度地区的暖湿气流入侵对罗斯冰架表面长波能量异常的贡献,揭示了引起冰架表面融化事件发生的原因。本次研究聚焦罗斯冰架有史以来最强烈的四次表面融化事件,发现融化事件发生期间均存在地表向下长波通量的激增现象。通过对云反馈过程、水汽反馈过程和大气动力反馈过程对向下长波辐射正异常贡献的定量分析,我们比较了四次融化事件中的主导过程。研究结果表明,来自低纬度海洋上空的暖湿气流的入侵,导致罗斯冰架上空的气温上升和水汽含量升高,并有利于云的生成;最终,云反馈过程、水汽反馈过程和大气反馈动力过程共同造成地表向下长波辐射异常增强,促成冰架表面升温和融化。