Hydrologic Responses to a Shrinking Arctic Sea Ice Cover

这一努力将检验这样一种假设，即北冰洋海冰和北部高纬度积雪的消失将引起北冰洋降水(P)和净降水量(P-E)的季节性、空间分布和大小的变化，这与随之而来的温度变化一起，对北冰洋的淡水平衡和格陵兰冰盖的物质平衡产生影响。研究人员预计：(A)海冰的消失将导致北冰洋及其周边海域可用水汽的增加，尤其是在秋季和冬季，此时延迟的结冰和变薄的冰将促进大量垂直热量和水分进入大气；(B)海冰和陆地积雪的丧失将引起北极环流模式的变化，从而导致水汽汇聚模式的变化，在秋冬季由于垂直热通量增加而受到驱动，并在暖季由于北冰洋和周围陆地上的差异加热而发生变化；(C)在北冰洋的“顺风向”以及毗邻(目前)部分被冰覆盖的东格陵兰海和巴芬湾的地方，格陵兰冰盖将通过对积累和表面融化的影响感受到这些变化。将对几个北极区域进行控制模拟，重点放在最近几年，这些区域的特点是9月海冰面积极低，由NCEP/NCAR再分析提供侧向强迫，以及由卫星观测确定的海冰条件。将生成的关键水文变量(可降水量、降水量、水汽通量辐合、净降水量、温度)和大气环流的场与一系列改变海冰和雪盖的实验所得的场进行对比。这些模拟将包括模拟整个年度周期的气候最大冬季冰范围和浓度、规定的冰范围和浓度减少量大于观测的值、全年周期内保持100%和0%的陆地积雪但具有观测到的海冰条件、以及观测到的海冰条件但夏季开放水域海面温度上升。

This effort will test the hypothesis that the loss of arctic sea ice and northern high latitude snow cover will invoke changes in the seasonality, spatial distribution and magnitudes of precipitation (P) and net precipitation (P-E) over the Arctic, which along with attendant changes in temperature, have ramifications for the freshwater budget of the Arctic Ocean and the mass balance of the Greenland ice sheet.The researchers expect that: (a) sea ice loss will lead to an increase in available water vapor over the Arctic Ocean and peripheral seas, most pronounced in autumn and winter, when delayed ice formation and thinner ice will promote large vertical fluxes of heat and moisture into the atmosphere; (b) loss of sea ice and terrestrial snow cover will invoke changes in arctic circulation patterns and hence patterns of water vapor convergence, driven in autumn and winter by enhanced vertical heat fluxes and during the warm season by altered differential heating over the Arctic Ocean and surrounding land; (c) in lying "downwind" of the Arctic Ocean as well as adjacent to the (presently) partially ice-covered East Greenland Sea and Baffin Bay, the Greenland ice sheet will feel these changes both through impacts on accumulation and surface melt.The analysis tool will be Polar WRF, a recently developed regional climate model optimized for polar applications. Control simulations will be conducted for several arctic domains, focusing on recent years which are characterized by extremely low September sea ice extent, with lateral forcing supplied from the NCEP/NCAR reanalysis, and sea ice conditions prescribed from satellite-based observations. Generated fields of key hydrologic variables (precipitable water, precipitation, vapor flux convergence, net precipitation, temperature) and atmospheric circulation will be contrasted with those from a series of experiments with altered sea ice and snow cover. These will include simulations with climatological maximum winter ice extent and concentration through the annual cycle, prescribed reductions in ice extent and concentration larger than those observed, 100% and 0% terrestrial snow cover maintained over the annual cycle but with observed sea ice conditions, and observed sea ice conditions but with increased sea surface temperature over open water areas in summer.