Late Glacial retreat of the Lancaster Sound Ice Sheet and early Holocene Parry Channel throughflow; 2008029-59CC (Composite Core), 2008029-49CC, 2013029-64PC (Piston Core) datasets (2008)

Multiple proxies in three sediment cores from Northwestern Baffin Bay document the timing of Lancaster Sound Ice Stream (LSIS) retreat that led to Arctic-Atlantic throughflow in Parry Channel, an important source of freshwater that can impact the Atlantic Meridional Overturning Circulation (AMOC). The Late Glacial to Holocene timing of ice retreat and channel opening and the responses of the regional ocean environment to these events are presented. We use quantitative mineral composition, foraminiferal assemblages, biogenic silica, ice-rafted debris (IRD), and 14C (carbon-14)-based age models to document and date the events and environmental changes occurring during deglaciation of this major marine channel. Findings show that retreat of the LSIS into Lancaster Sound occurred before ~15.3 cal ka BP (calculated kilo annum before present), about 800 years before the onset of major ice berg calving events from the LSIS, named the Baffin Bay Detrital carbonates events (BBDC 1 and BBDC 0). The end of BBDC 0 occurred at ~10.6 cal ka BP, which coincides with the opening of Parry Channel. A marine environment productive of calcareous benthic and planktic foraminifera, with diminished meltwater, seasonal sea ice, warmer summer temperatures and inflowing, nutrient-rich Arctic Surface Water characterizes the interval between the opening of Parry Channel and the opening of Nares Strait. Paired planktic and benthic 14C ages over this 2200-year interval show diminishing age offsets suggesting progressive mixing of the upper ~900 m (meters) of the water column. The opening of Nares Strait by ~8.2 cal ka BP coincides with increased biogenic silica in the form of abundant, large centric diatoms and dissolution of CaCO3 (calcium carbonate). The paucity of calcareous organisms after 8.2 cal ka BP resulted in poor chronological control in the cores to interpret changing environments after 8.2 cal ka BP.

来自巴芬湾西北部3个沉积岩芯的多类代用指标，记录了兰开斯特海峡冰流（Lancaster Sound Ice Stream, LSIS）的退缩时间——该冰流退缩使得帕里海峡成为北极-大西洋穿流通道，而帕里海峡是可影响大西洋经向翻转环流（Atlantic Meridional Overturning Circulation, AMOC）的重要淡水来源。本研究呈现了晚冰期至全新世期间的冰退与海峡开通时间，以及区域海洋环境对这些事件的响应。我们采用定量矿物组成、有孔虫组合、生物硅、冰筏碎屑（ice-rafted debris, IRD）以及基于碳-14（14C）的年代模型，对该大型海洋水道冰消期发生的事件与环境变化进行记录并定年。研究结果显示，LSIS退缩至兰开斯特海峡的时间约在距今15.3校准千年（calibrated kilo annum before present, cal ka BP）之前，比LSIS大规模冰山崩解事件——巴芬湾碎屑碳酸盐事件（BBDC 1与BBDC 0）的起始时间早约800年。BBDC 0事件结束于约距今10.6校准千年，这一时间与帕里海峡的开通相吻合。在帕里海峡开通至内尔斯海峡（Nares Strait）开通的时段内，区域海洋环境以钙质底栖与浮游有孔虫繁盛、融水减少、存在季节性海冰、夏季温度偏高以及流入富含营养的北极表层水为特征。该2200年时段内的浮游与底栖有孔虫成对14C测年结果显示，年龄差逐渐缩小，表明水柱上部约900米的水体混合作用逐步增强。约距今8.2校准千年时内尔斯海峡开通，这一事件与以丰富大型中心硅藻形式出现的生物硅增加以及碳酸钙（calcium carbonate, CaCO3）溶解相吻合。距今8.2校准千年之后，钙质生物匮乏导致岩芯的年代学控制精度降低，难以解释该时段之后的环境变化。