Seasonal Variations in Iceberg Freshwater Flux in Sermilik Fjord, Southeast Greenland From Sentinel-2 Imagery
Seasonal Variations in Iceberg Freshwater Flux in Sermilik Fjord, Southeast Greenland From Sentinel-2 Imagery
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DOI：
10.1029/2019gl082309
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发表时间：
2019-08-16
影响因子：
5.2
通讯作者：
Sole, A. J.
中科院分区：
文献类型：
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作者：
Moyer, A. N.;Sutherland, D. A.;Sole, A. J.
据估计，冰山排放的淡水占输送到冰川峡湾的淡水流量的50%。冰山融化的数量、时间和位置影响峡水循环和热量收支，并对冰川动力学、营养循环和峡湾生产力产生影响。我们使用Sentinel-2图像研究了2017-2018年夏季和2018年秋季格陵兰岛Sermilik Fjord开放水域冰山淡水通量的季节变化。利用目视跟踪得到的冰山速度和冰山总体积随离赫尔海姆冰川峡谷下移距离的变化，我们估计了5-6月、6-7月、7-8月、8-9月和9-11月全峡湾冰山淡水通量的最大平均值分别为1,060+/-615、1,270+/-735、1,200+/-700、3,410+/-1,975和1,150+/-670m(3)/S。通量随距离的降低而减小，平均86-91%的冰山体积在到达峡口之前消失。该方法为监测格陵兰地区的季节性和年际冰山淡水通量提供了一种简单、宝贵的工具。简明语言摘要最近的研究表明，冰山融化产生的淡水可以控制格陵兰冰盖周围冰川峡湾的淡水收支，这对海湾环流和热量收支、养分可获得性和初级生产力具有重要意义。在这里，我们使用卫星图像来估计2017-2018年格陵兰东南部塞米利克峡湾冰山的速度和冰山体积的季节变化，由此得出融水通量。冰山融化水通量在夏末和秋季最高，此时峡湾的水温比春季和初夏更高，而且有更多的冰山已经崩解到峡湾中。全年，冰山融化产生的淡水量大于进入冰川底部峡湾的淡水，这些淡水来自冰盖表面的融化。因此，冰山的融化为峡湾系统提供了大量淡水，对海湾尺度的循环和热量收支、营养循环和初级生产力具有重要影响。这里介绍的方法是有效、简单和廉价的，可以应用于各种冰川峡湾系统，特别是那些偏远和难以进入的系统。
Iceberg discharge is estimated to account for up to 50% of the freshwater flux delivered to glacial fiords. The amount, timing, and location of iceberg melting impacts fiord-water circulation and heat budget, with implications for glacier dynamics, nutrient cycling, and fiord productivity. We use Sentinel-2 imagery to examine seasonal variations in freshwater flux from open-water icebergs in Sermilik Fjord, Greenland during summer and fall of 2017-2018. Using iceberg velocities derived from visual-tracking and changes in total iceberg volume with distance down-fjord from Helheim Glacier, we estimate maximum average two-month full-fjord iceberg-derived freshwater fluxes of similar to 1,060 +/- 615, 1,270 +/- 735, 1,200 +/- 700, 3,410 +/- 1,975, and 1,150 +/- 670 m(3)/s for May-June, June-July, July-August, August-September, and September-November, respectively. Fluxes decrease with distance down-fiord, and on average, 86-91% of iceberg volume is lost before reaching the fiord mouth. This method provides a simple, invaluable tool for monitoring seasonal and interannual iceberg freshwater fluxes across a range of Greenlandic fiords.Plain Language Summary Recent studies have shown that the freshwater produced via the melting of icebergs can dominate the freshwater budget in glacial fjords surrounding the Greenland Ice Sheet, which has important implications for fiord circulation and heat budget, nutrient availability, and primary productivity. Here we use satellite imagery to estimate both iceberg velocity and the seasonal changes in iceberg volume in Sermilik Fjord in southeast Greenland in 2017-2018, from which meltwater fluxes are derived. Iceberg meltwater fluxes are highest in the late summer and fall, when fiord water temperatures are warmer than in the spring and early summer, and when more icebergs have been calved into the fjord. Throughout the year, the volume of freshwater generated from the melting of icebergs is greater than the freshwater entering the fjord at the base of the glacier and sourced from melting at the ice sheet surface. As such, the melting of icebergs provides a significant volume of freshwater to the fjord system, with important implications for fiord-scale circulation and heat budget, nutrient cycling, and primary productivity. The methodology presented here is effective, simple and inexpensive, and can be applied to a variety of glacial fiord systems, particularly those that are remote and inaccessible.