(Table 1) Arctic radiocarbon dates from sediment core PS1230-1

Ice sheets in the North American Arctic and, to a lesser extent, those in northern Eurasia calved large quantities of icebergs that drifted through Fram Strait into the Greenland Sea several times during the late Pleistocene. These icebergs deposited Fe oxide grains (45-250 mm) and coarse lithic clasts >250 mm matched to specific circum-Arctic sources. Four massive Arctic iceberg export events are identified from the Laurentide and the Innuitian ice sheets, between 14 and 34 ka (calendar years) in a sediment core from Fram Strait. These relatively short duration (<1-4 kyr) events contain 3-5 times the background levels of Fe oxide grains. They began suddenly, as indicated by a steep rise in the number of grains matched to an ice sheet source, suggesting rapid purges of ice through Fram Strait, due perhaps to collapse of ice sheets. The larger events from the northwestern Laurentide ice sheet are preceded by events from the Innuitian ice sheet. Despite the chronological uncertainties, the Arctic export events appear to occur prior to Heinrich events.

更新世晚期，北美北极地区的冰盖，以及规模相对较小的北欧亚北部冰盖，曾多次崩解出大量冰山；这些冰山经弗拉姆海峡（Fram Strait）漂流进入格陵兰海。这些冰山沉积了粒径45~250毫米的氧化铁颗粒（Fe oxide grains），以及粒径大于250毫米的粗粒岩屑砾石（lithic clasts），其物源可匹配至特定的环北极源区。基于弗拉姆海峡的一处沉积岩芯（sediment core），研究识别出4次大规模北极冰山输出事件，事件发生于14~34千年（日历年）期间，物源分别来自劳伦泰冰盖（Laurentide Ice Sheet）与因努伊特冰盖（Innuitian Ice Sheet）。这些事件的持续时间相对较短（<1~4千年），其中氧化铁颗粒的含量为背景水平的3~5倍。事件起始突然，匹配冰盖物源的颗粒数量陡增，这表明冰山经弗拉姆海峡的输出速率骤增，其诱因可能为冰盖崩解。源自劳伦泰冰盖西北部的规模更大的事件，其发生时间早于因努伊特冰盖相关的输出事件。尽管存在年代学上的不确定性，但北极冰山输出事件似乎均发生于海因里希事件（Heinrich events）之前。