一项研究认为,北极最大的现存冰架在过去10年中的崩溃不太可能是一个没有先例的事件。
人们把21世纪初Ward Hunt冰架的瓦解与近来北极的气候变暖联系了起来。这个冰架是在加拿大Ellesmere岛北部面积超过400平方公里的大块物质。
为了确定这个冰架崩溃以及随之而来的北极冰的损失是否反映了超出自然变动范围之外的环境状况,Dermot Antoniades及其同事分析了来自Disraeli峡湾的沉积物岩芯的特征,它的涨落状态反应了位于Disraeli峡湾出口处的这个冰架的状态,然后重建了在地质时间尺度上这个冰架的积累和崩溃。
这组作者提出,Ward Hunt冰架很可能是在不早于4000年前形成的,在大约1400年前断裂之前稳定存在了将近3000年。
这组作者提出,然后这个冰架很可能在800年前重新形成,但是在20世纪末上升的温度把这个冰架减少到了如今的小尺寸,并且让由它产生的一个湖干涸了。这组作者说,这些发现是向建立一个长期背景迈出的一步,有了这个背景,就可以评估目前北极冰的损失。(生物谷 Bioon.com)
doi:10.1073/pnas.1106378108
PMC:
PMID:
Holocene dynamics of the Arctic's largest ice shelf
Dermot Antoniades, Pierre Francus, Reinhard Pienitz, Guillaume St-Onge, and Warwick F. Vincent
Ice shelves in the Arctic lost more than 90% of their total surface area during the 20th century and are continuing to disintegrate rapidly. The significance of these changes, however, is obscured by the poorly constrained ontogeny of Arctic ice shelves. Here we use the sedimentary record behind the largest remaining ice shelf in the Arctic, the Ward Hunt Ice Shelf (Ellesmere Island, Canada), to establish a long-term context in which to evaluate recent ice-shelf deterioration. Multiproxy analysis of sediment cores revealed pronounced biological and geochemical changes in Disraeli Fiord in response to the formation of the Ward Hunt Ice Shelf and its fluctuations through time. Our results show that the ice shelf was absent during the early Holocene and formed 4,000 years ago in response to climate cooling. Paleoecological data then indicate that the Ward Hunt Ice Shelf remained stable for almost three millennia before a major fracturing event that occurred ∼1,400 years ago. After reformation ∼800 years ago, freshwater was a constant feature of Disraeli Fiord until the catastrophic drainage of its epishelf lake in the early 21st century.