The Northern Transpolar Gateways

在第三阶段期间，专题B1计划将其重点扩大到北欧海洋和北太平洋次极地之间的北部跨极门户连接。这个海道系统只在罕见的、持续时间很短的海平面极高的上/更新世间冰期开放，当时白令海峡被洪水淹没，现在的白令海峡深达45米。将讨论两个主要目标：(1)今天从北太平洋流向北极和北大西洋的由密度驱动的地表水流动可能发生逆转，以限制可能对全球温盐环流和气候的稳定产生的影响。这一目标将需要通过激光消融技术获得的稳定同位素和痕量金属数据的新质量，以重建过去海面分层的变化。(2)浮游有孔虫物种的跨极交换，这在理论上是可能的，但肯定是罕见的，更重要的是，在不同的厚皮有孔虫的进化和极地适应中的潜在种族。(NPS)北冰洋两岸的隐种，将通过过去3个月NPS及其谱系的形态测量记录来重建。(3)此外，新建立的基于44/40Ca的单个核动力源壳体的SST替代物现在将被用来限制丹麦海峡两侧在寒冷的Dansgaard-Oeschger冰期期间的古SST变化，并建立选定的晚上新世冰期和间冰期的古温度记录，这对于精确重建古密度梯度是必要的。

During Phase 3 Theme B1 is planning to expand its focus to the northern transpolar gateway connection between the Nordic Seas and the subpolar North Pacific. This seaway system was only open during rare and short-lasting Plio- / Pleistocene peak interglacials with extreme sealevel highstands, when the Bering Strait, today 45 m deep, was flooded. Two major objectives will be addressed: (1) Potential reversals in the density-driven flow of surface water today streaming from the North Pacific into the Arctic and North Atlantic, to constrain possible implications for the stability of global thermohaline circulation and climate. This target will require a new quality of stable-isotope and trace metal data obtained by laser ablation technique to reconstruct past variations in sea surface stratification. (2) The transpolar exchange of planktic foraminiferal species, which was possible by theory but certainly rare, and more important, the potential ¿race¿ in the evolution and extreme polar adaption of different N. pachyderma sin. (Nps) cryptospecies to both sides of the Arctic Sea, to be reconstructed by morphometric records of Nps and its lineages for the last 3 Myr. (3) In addition, the newly established ¿44/40Ca-based SST proxy of single Nps shells will now be employed to constrain paleo-SST variations to both sides of the Denmark Strait during cold Dansgaard-Oeschger stadials and to establish paleotemperature records for selected Late Pliocene glacial and interglacial stages, necessary for a precise reconstruction of paleodensity gradients.