Physical oceanography and current meter data from various moorings from the North Greenland Sea, list of links to datasets

We estimated the magnitude and composition of southward liquid freshwater transports in the East Greenland Current near 79° N in the Western Fram Strait between 1998 and 2011. Previous studies have found this region to be an important pathway for liquid freshwater export from the Arctic Ocean to the Nordic Seas and the North Atlantic subpolar gyre. Our transport estimates are based on six hydrographic surveys between June and September and concurrent data from moored current meters. We combined concentrations of liquid freshwater, meteoric water (river water and precipitation), sea ice melt and brine from sea ice formation, and Pacific Water, presented in Dodd et al. (2012, doi:10.1029/2012JC008011), with volume transport estimates from an inverse model. The average of the monthly snapshots of southward liquid freshwater transports between 10.6° W and 4° E is 100 ± 23 mSv (3160 ± 730 km**3/yr), relative to a salinity of 34.9. This liquid freshwater transport consists of about 130% water from rivers and precipitation (meteoric water), 30% freshwater from the Pacific, and -60% (freshwater deficit) due to a mixture of sea ice melt and brine from sea ice formation. Pacific Water transports showed the highest variation in time, effectively vanishing in some of the surveys. Comparison of our results to the literature indicates that this was due to atmospherically driven variability in the advection of Pacific Water along different pathways through the Arctic Ocean. Variations in most liquid freshwater component transports appear to have been most strongly influenced by changes in the advection of these water masses to the Fram Strait. However, the local dynamics represented by the volume transports influenced the liquid freshwater component transports in individual years, in particular those of sea ice melt and brine from sea ice formation. Our results show a similar ratio of the transports of meteoric water and net sea ice melt as previous studies. However, we observed a significant increase in this ratio between the surveys in 1998 and in 2009. This can be attributed to higher concentrations of sea ice melt in 2009 that may have been due to enhanced advection of freshwater from the Beaufort Gyre to the Fram Strait. Known trends and variability in the Arctic liquid freshwater inflow from rivers are not likely to have had a significant influence on the variation of liquid freshwater component transports between our surveys. On the other hand, known freshwater inflow variability from the Pacific could have caused some of the variation we observed in the Fram Strait. The apparent absence of a trend in southward liquid freshwater transports through the Fram Strait and recent evidence of an increase in liquid freshwater storage in the Arctic Ocean raise the question: how fast will the accumulated liquid freshwater be exported from the Arctic Ocean to the deep water formation regions in the North Atlantic and will an increased export occur through the Fram Strait.本研究估算了1998至2011年间，位于弗拉姆海峡（Fram Strait）西侧、北纬79°附近的东格陵兰海流（East Greenland Current）南向液态淡水输运的规模与组成。既往研究表明，该区域是北冰洋液态淡水向挪威海（Nordic Seas）与北大西洋副极地环流（North Atlantic subpolar gyre）输出的重要通道。 本次输运估算基于6次6月至9月间的海洋水文调查（hydrographic surveys）数据，以及同步获取的锚定海流计（moored current meters）观测资料。我们结合了Dodd等人（2012，DOI:10.1029/2012JC008011）发表的液态淡水、大气降水水（meteoric water，即河水与降水）、海冰融水及海冰形成过程产生的卤水、太平洋水（Pacific Water）的浓度数据，与反演模型（inverse model）得到的体积输运估算结果。以盐度34.9为参考基准，西经10.6°至东经4°区间内的南向液态淡水月均输运量为100±23毫斯维尔德鲁普（mSv，即3160±730 km³/年）。该南向液态淡水输运的组成大致为：河流水与降水（大气降水水）占比约130%，太平洋水来源的淡水占30%，而海冰融水与海冰形成产生的卤水混合导致的淡水亏缺占-60%（即淡水赤字）。 太平洋水来源的输运量时间变率最大，在部分海洋水文调查中几乎为零。将本研究结果与已有文献对比后可知，该现象源于太平洋水经北冰洋不同路径平流输送过程中受大气驱动的变率。多数液态淡水组分的输运变化，似乎主要受这些水团向弗拉姆海峡平流输送变化的影响。但在个别年份，以体积输运表征的局地动力过程会对液态淡水组分的输运产生影响，其中尤以海冰融水及海冰形成产生的卤水组分最为显著。 本研究结果显示，大气降水水与净海冰融水的输运占比与既往研究结果一致。但我们发现，1998年与2009年的两次调查之间，该占比出现了显著上升。该现象可归因于2009年海冰融水浓度更高，而这可能与波弗特环流（Beaufort Gyre）向弗拉姆海峡输送的淡水增强有关。 已知的北冰洋河流输入液态淡水的变化趋势与变率，不太可能对本研究各次调查间的液态淡水组分输运变化产生显著影响。另一方面，已知的太平洋淡水输入变率，可能是弗拉姆海峡观测到的部分输运变化的诱因。 弗拉姆海峡南向液态淡水输运未呈现明显趋势，加之近期有证据表明北冰洋液态淡水储量有所增加，这引发了一个核心问题：积累的液态淡水将以多快的速度从北冰洋向北大西洋深水形成区输出？且这种输出增量是否会通过弗拉姆海峡实现？