Water mass modification in an Arctic fjord through cross-shelf exchange: The seasonal hydrography of Kongsfjorden, Svalbard
Water mass modification in an Arctic fjord through cross-shelf exchange: The seasonal hydrography of Kongsfjorden, Svalbard
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DOI：
10.1029/2004jc002757
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发表时间：
2005-12-08
影响因子：
3.6
通讯作者：
Griffiths, C
中科院分区：
文献类型：
--
作者：
Cottier, F;Tverberg, V;Griffiths, C
[1]Kongsfjorden和West Spitsbergen Shelf是一个季节性水文地貌以大西洋水、北极水和冰川融化的平衡为主的地区。利用2000-2003年的电导率-温度-深度(CTD)观测和2002年春季和夏季为期5个月的系泊部署，研究了区域季节性和跨陆架交换过程。陆架-峡湾动力学模拟采用卑尔根海洋模式。观测显示，在仲夏期间，大西洋水迅速而压倒性地侵入大陆架并进入峡湾，导致了强烈的季节性。来自西斯皮茨卑尔根洋流的大西洋水通过陆架前缘的正压不稳定形成。它们泄漏到陆架上，并作为地形导向的特征向峡湾传播。模式结果表明，北风加强了这种跨锋交换。通常情况下，海湾口的密度锋阻止了大西洋水向峡湾的渗透。这种地转控制机制被发现比许多峡湾常见的液压控制更重要。在春季，峡湾水的缓慢变化降低了地转控制的有效性，到了仲夏，大西洋水侵入峡湾，从北极主导转变为大西洋主导。整个夏季，大西洋水继续入侵，到9月份达到某种准稳定状态。根据大西洋水域占有率的不同，峡湾采用“冷”或“暖”模式。大陆架的水平交换可能是导致向北向北极输送热量的季节变化的一个重要过程。
[1] Kongsfjorden and the West Spitsbergen Shelf is a region whose seasonal hydrography is dominated by the balance of Atlantic Water, Arctic waters, and glacial melt. Regional seasonality and the cross-shelf exchange processes have been investigated using conductivity-temperature-depth (CTD) observations from 2000 - 2003 and a 5-month mooring deployment through the spring and summer of 2002. Modeling of shelf-fjord dynamics was performed with the Bergen Ocean Model. Observations show a rapid and overwhelming intrusion of Atlantic Water across the shelf and into the fjord during midsummer giving rise to intense seasonality. Pockets of Atlantic Water, from the West Spitsbergen Current, form through barotropic instabilities at the shelf front. These leak onto the shelf and propagate as topographically steered features toward the fjord. Model results indicate that such cross-front exchange is enhanced by north winds. Normally, Atlantic Water penetration into the fjord is inhibited by a density front at the fjord mouth. This geostrophic control mechanism is found to be more important than the hydraulic control common to many fjords. Slow modification of the fjord water during spring reduces the effectiveness of geostrophic control, and by midsummer, Atlantic Water intrudes into the fjord, switching from being Arctic dominant to Atlantic dominant. Atlantic Water continues to intrude throughout the summer and by September reaches some quasi steady state condition. The fjord adopts a "cold'' or "warm'' mode according to the degree of Atlantic Water occupation. Horizontal exchange across the shelf may be an important process causing seasonal variability in the northward heat transport to the Arctic.