The presence of polynyas in the Weddell Sea during the Last Glacial Period with implications for the reconstruction of sea-ice limits and ice sheet history
The presence of polynyas in the Weddell Sea during the Last Glacial Period with implications for the reconstruction of sea-ice limits and ice sheet history
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末次冰期期间威德尔海冰间湖的存在对海冰界限和冰盖历史重建的影响
DOI：
10.1016/j.epsl.2010.05.008
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发表时间：
2010
影响因子：
5.3
通讯作者：
A. Graham
中科院分区：
文献类型：
--
作者：
James A. Smith;C. Hillenbrand;C. Pudsey;C. Allen;A. Graham
南极洲西北部威德尔海大陆坡等深流漂积岩岩芯中含有多达4个富含有孔虫的桑迪层（WA 1 -4），并有分散的冰筏碎屑（IRD），与粉质粘土砂和桑迪泥互层。对产于富有孔虫层WA 2和WA 3的Neogloboquadrina pachyderma进行了加速器质谱（AMS）~（14）C定年，得到的年龄分别跨越末次盛冰期（LGM）和海洋同位素阶段（MIS）2（20，319 -28，543 calyr BP）以及MIS 3的中部（41，349 -43，242 calyr BP）。我们的属性高丰度的浮游和底栖有孔虫沉积在季节性开放的海洋环境。考虑到西北威德尔海大陆架覆盖的接地冰在末次冰期（可能在MIS 2和MIS 3），并基于重建的地方北方限制冬季和夏季海冰覆盖的核心网站北部在末次冰期，我们的研究结果文件的存在下，一个季节性或常年冰间湖在西北威德尔海。冰间湖可能是由南极半岛冰盖（APIS）在大陆架断裂处搁浅时被吹离的下降风形成的，尽管不能排除深水上涌形成冰间湖的可能性。此外，我们认为，以前公布的数据从南部，东南部和西南部威德尔海以及罗斯海可能表明，广泛发生的冰穴沿着南极大陆边缘在末次冰期。冰穴的广泛出现有助于解释（i）AABW的形成（通过盐水排斥）如何在整个LGM中持续，以及（ii）南极大陆架底栖生物如何在冰川期存活下来。冰川期冰穴的存在也对冰芯记录的海冰重建有影响，可能会使信号偏向海冰覆盖减少。最后，我们建议，边缘的APIS，这可能会影响是否存在的冰穴在西北威德尔海，是敏感的南极温度的变化，可能与减少海洋热传输从北大西洋。
Cores from a contourite drift on the continental slope in the NW Weddell Sea, Antarctica, contain up to four sandy foraminifer-rich layers (WA1–4), with dispersed ice-rafted debris (IRD), interbedded with silty–clayey sands and sandy muds. Accelerator Mass Spectrometry (AMS)14C dating on Neogloboquadrina pachyderma from the foraminifer-rich layers WA2 and WA3 yielded ages spanning the Last Glacial Maximum (LGM) and Marine Isotope Stage (MIS) 2 (20,319–28,543calyr BP) and the middle part of MIS 3 (41,349–43,242calyr BP), respectively. We attribute the high abundances of planktonic and benthic foraminifera to deposition in a seasonally open-marine environment. Given that the NW Weddell Sea shelf was covered by grounded ice at the LGM (and probably during MIS 2 and MIS 3) and that diatom-based reconstructions place the northern limit of winter and summer sea-ice coverage to the north of the core sites during the Last Glacial Period, our results document the presence of a seasonal or perennial polynya in the NW Weddell Sea. The polynya may have been formed by katabatic winds blowing off the Antarctic Peninsula Ice Sheet (APIS) when it was grounded at the continental shelf break, although polynya formation through upwelling of deep water cannot be ruled out. In addition we argue that previously published data from the southern, southeastern and southwestern Weddell Sea as well as the Ross Sea may indicate the widespread occurrence of polynyas along the Antarctic continental margin during the Last Glacial Period. The widespread occurrence of polynyas could help explain how (i) AABW formation (through brine rejection) continued throughout the LGM, and (ii) Antarctic shelf benthos survived glacial periods. The presence of polynyas through glacial periods also has implications for sea-ice reconstructions from ice core records, possibly biasing the signal towards a reduced sea-ice cover. Finally we propose that the fringes of the APIS, which probably influence the presence or absence of polynyas in the NW Weddell Sea, are sensitive to changes in Antarctic temperature that may be related to a reduction in oceanic heat transport from the North Atlantic.
影响因子：
4
作者：
Gersonde, R;Crosta, X;Armand, L
通讯作者：
Armand, L