Atmospheric Drivers of Melt on Larsen C Ice Shelf: Surface Energy Budget Regimes and the Impact of Foehn
Atmospheric Drivers of Melt on Larsen C Ice Shelf: Surface Energy Budget Regimes and the Impact of Foehn
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DOI：
10.1029/2020jd032463
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发表时间：
2020-09-16
影响因子：
4.4
通讯作者：
Gilbert, Ella
中科院分区：
文献类型：
--
作者：
Elvidge, Andrew D.;Kuipers Munneke, Peter;Gilbert, Ella
最近南极半岛东海岸的冰架退缩主要归因于大气驱动的融化。然而，之前对这些冰架中最大的一个——拉森冰架（Larsen C）的研究一直在努力协调大气强迫与观测到的融化。这项研究利用内阁入口 31 个月的观测、为期 6 个月的高分辨率大气模型模拟和一种确定表面能量收支 (SEB) 状况的新方法，首次对拉森 C 融化的大气驱动因素进行了全面的量化和解释。研究表明，对融化的主要气象控制是被称为焚风的山风的出现、强度和温暖。在 Cabinet Inlet，焚风发生的时间为 15%，并导致 45% 的熔化。焚风对 SEB 的主要影响是增加湍流热通量。在典型的温暖焚风条件下，这意味着表面加热和融化程度升高，其强度随着焚风风速的增加而增加。不太常见的是，由于比正常温度低的焚风和/或辐射变暖的冰，风速和净表面热通量之间的关系会发生逆转。这解释了先前研究看似矛盾的结果。在模型中，拉森 C 累积融化量的空间变化主要由焚风来解释，入口处的融化最大值反映了焚风风强度的最大值。然而，大多数累积融化（58%）是在没有焚风的情况下由于太阳辐射而发生的。焚风和非焚风条件的综合影响解释了熔融的广泛南北梯度。
Recent ice shelf retreat on the east coast of the Antarctic Peninsula has been principally attributed to atmospherically driven melt. However, previous studies on the largest of these ice shelves-Larsen C-have struggled to reconcile atmospheric forcing with observed melt. This study provides the first comprehensive quantification and explanation of the atmospheric drivers of melt across Larsen C, using 31-months' worth of observations from Cabinet Inlet, a 6-month, high-resolution atmospheric model simulation and a novel approach to ascertain the surface energy budget (SEB) regime. The dominant meteorological controls on melt are shown to be the occurrence, strength, and warmth of mountain winds called foehn. At Cabinet Inlet, foehn occurs 15% of the time and causes 45% of melt. The primary effect of foehn on the SEB is elevated turbulent heat fluxes. Under typical, warm foehn conditions, this means elevated surface heating and melting, the intensity of which increases as foehn wind speed increases. Less commonly-due to cooler-than-normal foehn winds and/or radiatively warmed ice-the relationship between wind speed and net surface heat flux reverses. This explains the seemingly contradictory results of previous studies. In the model, spatial variability in cumulative melt across Larsen C is largely explained by foehn, with melt maxima in inlets reflecting maxima in foehn wind strength. However, most accumulated melt (58%) occurs due to solar radiation in the absence of foehn. A broad north-south gradient in melt is explained by the combined influence of foehn and non-foehn conditions.