Snow contribution to first-year and second-year Arctic sea ice mass balance north of Svalbard
Snow contribution to first-year and second-year Arctic sea ice mass balance north of Svalbard
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DOI：
10.1002/2016jc012398
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发表时间：
2017-03-01
影响因子：
3.6
通讯作者：
Leng, Melanie J.
中科院分区：
文献类型：
--
作者：
Granskog, Mats A.;Rosel, Anja;Leng, Melanie J.
对来自斯瓦尔巴特群岛北部浮冰群的29个第一年（FYI）和第二年（SYI）北极海冰芯（总长度32.0 m）的盐度和水氧同位素组成（δ O-18）进行了研究，以量化雪对海冰质量的贡献。分析了五个岩心（总长度6.4米）的结构组成，显示出10-30%的颗粒冰的可变贡献。在这些冰芯中，雪被夹带在总冰厚度的6-28%中。我们发现的证据，雪的贡献，在约四分之三的海冰核心，当表面颗粒层有非常低的三角洲O-18值。根据δ O-18质量平衡计算，雪对海冰质量平衡的平均贡献率为7.5-9.7%（包括无雪的核心）。在SYI岩心中，雪质量分数（12.7-16.3%）远高于FYI岩心（3.3-4.4%），而FYI（4.9）的总盐度明显高于SYI（2.7）。我们的结论是，氧同位素和盐度配置文件可以给信息的年龄的冰，并使FYI和SYI（或更老）冰之间的区别在该地区北部的斯瓦尔巴特群岛。简单的语言摘要雪在海冰质量平衡的作用主要是双重的。首先，由于其高绝缘性和高反射率，它可以减缓生长和融化，但其次，如果积雪变成冰，它实际上可以促进海冰的生长。后者主要是海冰上大量积雪的结果，这些积雪可以将海冰表面推到海平面以下，海水可以淹没冰层。这种海水和雪的混合物可以冻结并增加海冰的生长。这在南极非常典型，但在北极并不那么重要。在这项工作中，我们第一次表明，雪实际上对北极海冰的增长有很大的贡献。这可能是北极海冰变薄的结果。因此，北极的条件与南极的冰层相似，冰更薄，季节性更强。研究北极雪的作用对于了解北极海冰的持续变化至关重要。
The salinity and water oxygen isotope composition (delta O-18) of 29 first-year (FYI) and second-year (SYI) Arctic sea ice cores (total length 32.0 m) from the drifting ice pack north of Svalbard were examined to quantify the contribution of snow to sea ice mass. Five cores (total length 6.4 m) were analyzed for their structural composition, showing variable contribution of 10-30% by granular ice. In these cores, snow had been entrained in 6-28% of the total ice thickness. We found evidence of snow contribution in about three quarters of the sea ice cores, when surface granular layers had very low delta O-18 values. Snow contributed 7.5-9.7% to sea ice mass balance on average (including also cores with no snow) based on delta O-18 mass balance calculations. In SYI cores, snow fraction by mass (12.7-16.3%) was much higher than in FYI cores (3.3-4.4%), while the bulk salinity of FYI (4.9) was distinctively higher than for SYI (2.7). We conclude that oxygen isotopes and salinity profiles can give information on the age of the ice and enables distinction between FYI and SYI (or older) ice in the area north of Svalbard.Plain Language Summary The role of snow in sea ice mass balance is largely two fold. Firstly, it can slow down growth and melt due to its high insulation and high reflectance, but secondly it can actually contribute to sea ice growth if the snow cover is turned into ice. The latter is largely a consequence of high mass of snow on top of sea ice that can push the surface of the sea ice below sea level and seawater can flood the ice. This mixture of seawater and snow can then freeze and add to the growth of sea ice. This is very typical in the Antarctic but not believed to be so important in the Arctic. In this work we show, for the first time, that snow actually contributes significantly to the growth of Arctic sea ice. This is likely a consequence of the thinning of the Arctic sea ice. The conditions in the Arctic, with thinner and more seasonal ice thus resemble the ice pack in the Antarctic. Studies on the role of snow in the Arctic are critical to be able to understand the ongoing changes of the Arctic sea ice pack.