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Millennial‐Scale Changes in Bottom Water Temperature and Water Mass Exchange Through the Fram Strait 79°N, 63‐13 ka
Paleoceanography and Paleoclimatology ( IF 3.2 ) Pub Date : 2020-12-31 , DOI: 10.1029/2020pa004061
N. El bani Altuna 1 , M. M. Ezat 1, 2 , M. Greaves 3 , T. L. Rasmussen 1
Affiliation  

The Svalbard margin, in the eastern Fram Strait with its high sediment accumulation, form a key area for the reconstruction of water mass and heat exchange between the North Atlantic and Arctic Ocean in relation to abrupt climate changes as seen in glacial Greenland Interstadial and Greenland Stadial (GI‐GS) events. Here, we present a bottom water temperature (BWT) record from the northern Nordic Seas (79°N) at 1,273 m water depth based on benthic foraminiferal Mg/Ca. The BWT reconstructions, combined with benthic foraminiferal stable isotopes, benthic foraminiferal fauna compositions and ice‐rafted debris (IRD), reveal at least two distinctive scenarios for the GI‐GS events during the last glacial period (13–63 ka). During GIs, conditions were similar to modern with high productivity, low BWT and deep convection. During GS6, GS8, and GS15 and during Heinrich Stadials (HSs), BWT increased up to 5°C ± 1°C generally concomitant with low planktic and benthic δ18O. Our results suggest, that during some GSs and HSs, deep water generation was reduced, allowing the subsurface Atlantic water (AW) to thicken and deepen down to at least the core site depth. A strong halocline during HSs and GSs prevented heat release from the subsurface AW, which we can now trace from 45°N in the North Atlantic to the Arctic Ocean >79°N. Surfacing of the salty Atlantic subsurface water preconditioned the Nordic seas for convection. Release of the subsurface heat from this vast reservoir must have contributed to the large and abrupt atmospheric warmings at the start of GIs.

中文翻译:

通过弗拉姆海峡79°N,63-13 ka的底水温度和水质交换的千年尺度变化

弗拉姆海峡东部的斯瓦尔巴特边缘具有高沉积物积聚,这是重建北大西洋和北冰洋之间水量和热交换与气候突变相关的关键区域,如冰川格陵兰洲际和格陵兰体育场(GI‐GS)事件。在这里,我们根据底栖有孔虫的Mg / Ca得出北部北欧海(79°N)在1,273 m水深处的底水温度(BWT)记录。BWT重建与底栖有孔虫稳定同位素,底栖有孔虫动物区系组成和冰屑残骸(IRD)相结合,揭示了上一个冰期(13–63 ka)至少发生了GI-GS事件的两种不同情况。在地理标志期间,条件与现代相似,具有高生产率,低BWT和深对流的特点。在GS6,GS8期间,18 O.我们的结果表明,在某些GS和HS期间,深水生成减少,从而使大西洋地下水(AW)增稠并加深到至少核心位置深度。HS和GS期间强烈的盐环阻止了地下AW放热,现在我们可以从北大西洋的45°N到> 79°N的北冰洋追踪到。咸的大西洋地下水的铺面使北欧海洋得以对流。从这个巨大的储层中释放出的地下热量必定导致了地理标志开始时大气的突然急剧变暖。
更新日期:2021-02-18
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