Reconstruction of Holocene oceanographic conditions in eastern Baffin Bay
Reconstruction of Holocene oceanographic conditions in eastern Baffin Bay
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DOI：
10.5194/cp-16-1075-2020
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发表时间：
2020-06-22
影响因子：
4.3
通讯作者：
Seidenkrantz, Marit-Solveig
中科院分区：
文献类型：
--
作者：
Hansen, Katrine Elnegaard;Giraudeau, Jacques;Seidenkrantz, Marit-Solveig
巴芬湾是连接北冰洋和北大西洋西部的半封闭盆地，为热交换提供了重要的通道。在这里，我们重建了全新世期间相对温暖和含盐的大西洋海水交替平流与较冷的北极水团通过加拿大北极群岛和纳尔斯海峡的多个门户进入巴芬湾的过程。我们对在格陵兰乌佩纳维克附近的巴芬湾东部采集的738厘米长的海洋沉积物岩心进行了底栖有孔虫组合分析、x射线荧光扫描和放射性碳定年（岩心AMD14-204C；水深987 m）。结果表明，巴芬湾东部在近9.2 kyr期间经历了多次海洋变化。在9.2至7.9 ka期间，巴芬湾东部冰川消融条件减弱，融水流量增加，海冰覆盖广泛。在7.9 ka，大西洋水团平流增加，记录了向底层水改善的转变，包括全新世热极大期。在6.7 ka海冰覆盖增加的寒冷期中断了整个温暖的地下水条件，这是由大西洋水域较弱的北流推动的。大约2.9 ka的新冰期的开始标志着向以粘连物种为主的底栖动物群的突然转变，部分原因可能是大西洋水流入的减少，使得来自北冰洋的寒冷、腐蚀性的巴芬湾深水通过纳尔斯海峡流入巴芬湾。这些寒冷的地下水状况持续了整个全新世晚期，只是被叠加在这种冷却趋势上的短暂变暖所中断。
Baffin Bay is a semi-enclosed basin connecting the Arctic Ocean and the western North Atlantic, thus making out a significant pathway for heat exchange. Here we reconstruct the alternating advection of relatively warmer and saline Atlantic waters versus the incursion of colder Arctic water masses entering Baffin Bay through the multiple gateways in the Canadian Arctic Archipelago and the Nares Strait during the Holocene. We carried out benthic foraminiferal assemblage analyses, X-ray fluorescence scanning, and radiocarbon dating of a 738 cm long marine sediment core retrieved from eastern Baffin Bay near Upernavik, Greenland (Core AMD14-204C; 987 m water depth). Results reveal that eastern Baffin Bay was subjected to several oceanographic changes during the last 9.2 kyr. Waning deglacial conditions with enhanced meltwater influxes and an extensive sea-ice cover prevailed in eastern Baffin Bay from 9.2 to 7.9 ka. A transition towards bottom water amelioration is recorded at 7.9 ka by increased advection of Atlantic water masses, encompassing the Holocene Thermal Maximum. A cold period with growing sea-ice cover at 6.7 ka interrupts the overall warm subsurface water conditions, promoted by a weaker northward flow of Atlantic waters. The onset of the neoglaciation at ca. 2.9 ka is marked by an abrupt transition towards a benthic fauna dominated by agglutinated species, likely in part explained by a reduction of the influx of Atlantic Water, allowing an increased influx of the cold, corrosive Baffin Bay Deep Water originating from the Arctic Ocean to enter Baffin Bay through the Nares Strait. These cold subsurface water conditions persisted throughout the Late Holocene, only interrupted by short-lived warmings superimposed on this cooling trend.