Evolution of a Canada Basin ice-ocean boundary layer and mixed layer across a developing thermodynamically forced marginal ice zone
Evolution of a Canada Basin ice-ocean boundary layer and mixed layer across a developing thermodynamically forced marginal ice zone
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DOI：
10.1002/2016jc011778
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发表时间：
2016-08-01
影响因子：
3.6
通讯作者：
Hwang, Byongjun
中科院分区：
文献类型：
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作者：
Gallaher, Shawn G.;Stanton, Timothy P.;Hwang, Byongjun
在加拿大盆地收集了一套全面的自主冰-海测量数据，以研究冰-海边界层（IOBL）和海洋混合层（OML）的夏季演变。当地的热量和淡水平衡和相关的湍流强迫的评估表明，融化池（MP）强烈影响夏季IOBL-OML演变。在6月中旬，MP的面积扩张开始了上层海洋的演变，导致海洋吸收的辐射通量显着增加（本研究中为19 W m（-2））。MP排水浅滩提供的浮力使IOBL变新鲜，导致在短短19天内热储存增加39 MJ m（-2）（占夏季总量的52%）。MP排水后，近地表新鲜层加深，通过剪切力混合，形成夏季混合层（sML）。在夏末，由于较强的湍流混合在薄的sML和开放水域的扩大，部分由于风迫使海冰的发散，基底融化增加。边缘冰区（MIZ）上层海洋的热不均匀性导致了大的海洋-冰热通量（100-200 W m（-2））和增强的基底冰融化（36 cm d（-1）），远离冰边缘。对上层海洋热量收支的计算表明，在观测到的潜热损失和热储存中，局地辐射热输入至少占89%（0.77/0.23）。这些结果表明，在2014年季节，远离冰缘观察到的海冰恶化的大面积区域，称为“受气候影响的MIZ”，主要是由当地短波辐射强迫驱动的。
A comprehensive set of autonomous, ice-ocean measurements were collected across the Canada Basin to study the summer evolution of the ice-ocean boundary layer (IOBL) and ocean mixed layer (OML). Evaluation of local heat and freshwater balances and associated turbulent forcing reveals that melt ponds (MPs) strongly influence the summer IOBL-OML evolution. Areal expansion of MPs in mid-June start the upper ocean evolution resulting in significant increases to ocean absorbed radiative flux (19 W m(-2) in this study). Buoyancy provided by MP drainage shoals and freshens the IOBL resulting in a 39 MJ m(-2) increase in heat storage in just 19 days (52% of the summer total). Following MP drainage, a near-surface fresh layer deepens through shear-forced mixing to form the summer mixed layer (sML). In late summer, basal melt increases due to stronger turbulent mixing in the thin sML and the expansion of open water areas due in part to wind-forced divergence of the sea ice. Thermal heterogeneities in the marginal ice zone (MIZ) upper ocean led to large ocean-to-ice heat fluxes (100-200 W m(-2)) and enhanced basal ice melt (36 cm d(-1)), well away from the ice edge. Calculation of the upper ocean heat budget shows that local radiative heat input accounted for at least 89% of the observed latent heat losses and heat storage (partitioned 0.77/0.23). These results suggest that the extensive area of deteriorating sea ice observed away from the ice edge during the 2014 season, termed the "thermodynamically forced MIZ," was driven primarily by local shortwave radiative forcing.