The Northern Transpolar Gateways

在第三阶段，主题B1计划将其重点扩大到北欧海与次极地北太平洋之间的北部跨极门户连接。这条海道系统只在罕见的、持续时间较短的上新世/更新世间冰期高峰时期开放，那时海平面高度极高，白令海峡（今天45米深）被淹没。研究将涉及两个主要目标：(1)目前从北太平洋流入北极和北大西洋的密度驱动的地表水流的潜在逆转，以限制对全球温盐环流和气候稳定性的可能影响。这一目标将需要通过激光烧蚀技术获得新的稳定同位素和痕量金属数据，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，在不同厚皮木的进化和极端极地适应中潜在的“种族”。（Nps）在北冰洋两岸的隐种，通过近3万年Nps及其谱系的形态测量记录进行重建。(3)此外，新建立的基于¿44/ 40ca的单一Nps壳的海温代理现在将用于约束丹麦海峡两岸在寒冷的Dansgaard-Oeschger冰期的古海温变化，并建立特定的晚上新世冰期和间冰期的古温度记录，这是精确重建古密度梯度所必需的。

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.