Major surface melting over the Ross Ice Shelf part I: Foehn effect
Major surface melting over the Ross Ice Shelf part I: Foehn effect
复制标题
DOI：
10.1002/qj.4104
复制
发表时间：
2021-06
影响因子：
8.9
通讯作者：
Xun Zou;D. Bromwich;Á. Montenegro;Sheng‐Hung Wang;L. Bai
中科院分区：
文献类型：
--
作者：
Xun Zou;D. Bromwich;Á. Montenegro;Sheng‐Hung Wang;L. Bai
近年来，南极洲西部，特别是罗斯冰架（RIS），经历了更为频繁的表面融化。未来很可能会看到表面融化加剧，这将危及冰架的稳定性并导致冰损失。我们通过极地天气研究和预报（WRF）模拟（4 km分辨率）调查了RIS上的四个主要融化案例，这些模拟由欧洲中期天气预报中心（ECMWF）再分析第五代（ERA 5）再分析数据和中分辨率成像光谱仪（MODIS）观测到的数据驱动。直接暖空气平流、反复焚风效应和云/高层暖空气引起的辐射增暖是西澳大利亚州地面融化的三个主要区域性原因。本文第一部分，对前两个因素进行了识别和量化。第二篇论文，第二部分，讨论了云的影响，并从表面能量平衡的角度总结了所有三个因素。高压脊位于苏兹贝格冰架向西（77° S，148° W），低压中心位于165°和180° W之间，来自罗斯海的温暖海洋空气平流流向沿海RIS，导致表面融化。当高压脊位于更远的东部，朝向玛丽伯德地（120-150° W）时，焚风效应可导致山脉背风面的表面温度升高2-4°C。对于四分之三的融化案例，超过40%的融化期经历焚风变暖。等熵降落通常是主要的焚风机制，并导致高达14°C的温度升高，特别是当逆风侧发生强烈的低层阻塞时。热力学机制可能是重要的，取决于迎风面的水分吸收和凝结的强度。同时，感热通量对焚风增温的贡献较小，但对焚风融化仍起着重要作用。RIS未来稳定性的预测应包括焚风变暖作为一个主要的驱动力。
West Antarctica (WA), especially the Ross Ice Shelf (RIS), has experienced more frequent surface melting during the austral summer recently. The future is likely to see enhanced surface melting that will jeopardize the stability of ice shelves and cause ice loss. We investigate four major melt cases over the RIS via Polar Weather Research and Forecasting (WRF) simulations (4 km resolution) driven by European Centre for Medium‐Range Weather Forecasts (ECMWF) Reanalysis 5th Generation (ERA5) reanalysis data and Moderate Resolution Imaging Spectroradiometer (MODIS) observed albedo. Direct warm air advection, recurring foehn effect, and cloud/upper warm air introduced radiative warming are the three major regional causes of surface melting over WA. In this paper, Part I, the first two factors are identified and quantified. The second paper, Part II, discusses the impact of clouds and summarizes all three factors from a surface energy balance perspective. With a high‐pressure ridge located westward towards the Sulzberger Ice Shelf (77° S, 148° W) and a low‐pressure center located between 165° and 180° W, warm marine air from the Ross Sea is advected towards the coastal RIS and leads to surface melting. When the high‐pressure ridge is located farther east towards Marie Byrd Land (120–150° W), the foehn effect can cause a 2–4°C increase in surface temperature on the leeside of the mountains. For three of four melt cases, more than 40% of the melting period experiences foehn warming. Isentropic drawdown is usually the dominant foehn mechanism and contributes up to a 14°C temperature increase, especially when strong low‐level blocking occurs on the upwind side. The thermodynamic mechanism can be important depending on the strength of moisture uptake and condensation on the windward side. Meanwhile, sensible heat flux contributes less to foehn warming, but still plays an important role in the melting. The prediction of future stability of the RIS should include foehn warming as a major driver.