Tracer studies of pathways and rates of meltwater transport through Arctic summer sea ice
Tracer studies of pathways and rates of meltwater transport through Arctic summer sea ice
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DOI：
10.1029/2000jc000583
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发表时间：
2002-09-01
影响因子：
3.6
通讯作者：
Perovich, DK
中科院分区：
文献类型：
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作者：
Eicken, H;Krouse, HR;Perovich, DK
在楚科奇海北部的北冰洋表面热量收支 (SHEBA) 项目现场，发现冰雪融水流动对 1998 年夏季海冰的热量和质量平衡有很大影响。融水输送的路径和速率源自示踪剂研究（H-2 O-18、Be-7 和荧光染料的释放），并辅以现场海冰渗透性测量。结果表明，地表融水供应（平均在3.5至10.5 mm d(-1)之间）和冰渗透性（在10(-9) m(2)之间）之间的平衡决定了融水的保留和汇集，进而控制了冰反照率。我们发现，第一年和多年冰渗透性和表面形态的季节性演变决定了四个不同的融化阶段。在消融季节（第一阶段）开始时，积水很普遍，横向熔体流动占主导地位。研究发现，每天有数十立方米的融水通过裂缝和渗透区排出数百至数千平方米的冰。这些排水点形成了大量的水下冰，其中 50% 为大气降水。积雪完全去除，冰渗透性增加，驱动流体流动的水力梯度减少，标志着第二阶段，同时池塘覆盖率和反照率减少。在第三阶段，测量了最大渗透率，表面融水渗透到冰中 1 m 深度，发现对流翻转和海水淡化在第一年和薄多年冰的下层中占主导地位。据观察，流入裂缝和渗透区的流体流量增加会促进浮冰破裂和崩解，同时池塘盐度和 Be-7 也会增加。每平方米产生几十瓦的平流热流，促进了池塘的扩大和池塘覆盖面积的增加。第 4 阶段对应于冻结。大约 40% 的总表面融化量被冰基质内以及地表和冰下池塘中的冰盖截留（总净截留率为 15%）。基于这项工作，确定了冰反照率完全预测模拟的改进领域，要求对海冰渗透性进行参数化，并将冰地形和精细的消融方案整合到大气-冰-海洋模型中。
At the Surface Heat Budget of the Arctic Ocean (SHEBA) program's field site in the northern Chukchi Sea, snow and ice meltwater flow was found to have a strong impact on the heat and mass balance of sea ice during the summer of 1998. Pathways and rates of meltwater transport were derived from tracer studies (H-2 O-18, Be-7, and release of fluorescent dyes), complemented by in situ sea-ice permeability measurements. It was shown that the balance between meltwater supply at the surface (averaging between 3.5 and 10.5 mm d(-1)) and ice permeability (between 10(-9) m(2)) determines the retention and pooling of meltwater, which in turn controls ice albedo. We found that the seasonal evolution of first-year and multiyear ice permeability and surface morphology determine four distinct stages of melt. At the start of the ablation season (stage 1), ponding is widespread and lateral melt flow dominates. Several tens of cubic meters of meltwater per day were found to drain hundreds to thousands of square meters of ice through flaws and permeable zones. Significant formation of underwater ice, composed between 50% of meteoric water, formed at these drainage sites. Complete removal of snow cover, increase in ice permeability, and reductions in hydraulic gradients driving fluid flow mark stage 2, concurrent with a reduction in pond coverage and albedo. During stage 3, maximum permeabilities were measured, with surface meltwater penetrating to 1 m depth in the ice and convective overturning and desalination found to dominate the lower layers of first-year and thin multiyear ice. Enhanced fluid flow into flaws and permeable zones was observed to promote ice floe breakup and disintegration, concurrent with increases in pond salinities and Be-7. Advective heat flows of several tens of watts per square meter were derived, promoting widening of ponds and increases in pond coverage. Stage 4 corresponds to freeze-up. Roughly 40% of the total surface melt was retained by the ice cover within the ice matrix as well as in surface and under-ice ponds (with a total net retention of 15%). Based on this work, areas of improvement for fully prognostic simulations of ice albedo are identified, calling for parameterizations of sea-ice permeability and the integration of ice topography and refined ablation schemes into atmosphere-ice-ocean models.