Holocene lowering of the Laurentide ice sheet affects North Atlantic gyre circulation and climate
Holocene lowering of the Laurentide ice sheet affects North Atlantic gyre circulation and climate
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全新世劳伦太德冰盖降低影响北大西洋环流和气候
DOI：
10.1007/s00382-018-4111-9
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发表时间：
2018
期刊：
影响因子：
4.6
通讯作者：
Gregoire L
中科院分区：
文献类型：
--
作者：
Gregoire L
劳伦蒂德冰盖在冰川时期覆盖了加拿大，对大气环流和地表气候产生了重大影响，但它在全新世早期(9-7世纪)的气候中的作用尚不清楚，当时它较薄，仅限于哈德逊湾周围。有人认为，冰盖的消亡通过地形变化对大气环流的影响，在8.2Gka事件(北半球1-3℃的突然降温持续了 ~ 160a)中发挥了作用。为了验证这一假设，并调查冰盖地形变化对气候的更广泛影响，我们分析了一组平衡气候模拟，其中冰盖地形在9.5亿到8.0亿年间间隔500年采集。在9.5到8.0摄氏度之间，我们的模拟显示冰岛南部的气温下降了2摄氏度，北大西洋在40摄氏度到50摄氏度之间升温了1摄氏度。这些表面温度的变化与副热带和亚极地涡旋的减弱有关，这是由于北大西洋中部的风应力卷曲随着冰盖的降低而减弱。冰量变化峰值时期(9.5-8.5 kka)的气候响应最强，但在8.5-8.5ka之后，气候响应变得微乎其微。Laurentide冰盖在全新世期间下降的气候影响仅限于北大西洋地区。因此，地形强迫不太可能在8.2千卡事件中发挥主要作用，与温室气体、日照和冰盖融化的影响相比，对全新世气候变化的影响很小。
The Laurentide ice sheet, which covered Canada during glacial periods, had a major influence on atmospheric circulation and surface climate, but its role in climate during the early Holocene (9–7 ka), when it was thinner and confined around Hudson Bay, is unclear. It has been suggested that the demise of the ice sheet played a role in the 8.2 ka event (an abrupt 1–3 °C Northern Hemisphere cooling lasting ~ 160 years) through the influence of changing topography on atmospheric circulation. To test this hypothesis, and to investigate the broader implications of changing ice sheet topography for climate, we analyse a set of equilibrium climate simulations with ice sheet topographies taken at 500 year intervals from 9.5 to 8.0 ka. Between 9.5 and 8.0 ka, our simulations show a 2 °C cooling south of Iceland and a 1 °C warming between 40° and 50°N in the North Atlantic. These surface temperature changes are associated with a weakening of the subtropical and subpolar gyres caused by a decreasing wind stress curl over the mid-North Atlantic as the ice sheet lowers. The climate response is strongest during the period of peak ice volume change (9.5–8.5 ka), but becomes negligible after 8.5 ka. The climatic effects of the Laurentide ice sheet lowering during the Holocene are restricted to the North Atlantic sector. Thus, topographic forcing is unlikely to have played a major role in the 8.2 ka event and had only a small effect on Holocene climate change compared to the effects of changes in greenhouse gases, insolation and ice sheet meltwater.
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