Persistent influence of ice sheet melting on high northern latitude climate during the early Last Interglacial
Persistent influence of ice sheet melting on high northern latitude climate during the early Last Interglacial
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DOI：
10.5194/cp-8-483-2012
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发表时间：
2012-01-01
影响因子：
4.3
通讯作者：
Waelbroeck, C.
中科院分区：
文献类型：
--
作者：
Govin, A.;Braconnot, P.;Waelbroeck, C.
虽然末次间冰期（LIG）经常被认为是高纬度地区未来气候的可能模拟，但其精确的气候演变及其相关原因仍不确定。在这里，我们收集了来自北大西洋、拉布拉多海、挪威海和南大洋的高分辨率海洋沉积物记录。我们记录了与南大洋相比，北大西洋、拉布拉多海和挪威海的间冰期峰值条件的建立延迟。特别是，我们观察到，在LIG开始时，北纬高纬度地区的冰山持续融化。它与(1)北大西洋、拉布拉多海和挪威海的地表水条件更冷、更新鲜，以及(2)在LIG早期（129-125 ka）与LIG晚期相比，北大西洋深水的通风较弱有关。在LIG的三个关键时期，以日照为唯一强迫的海洋-大气耦合模式的结果显示，LIG早期（126 ka）北大西洋表层水比LIG晚期（122 ka）更温暖，大西洋翻转更强烈。因此，单独的日照变化不能解释在北纬高纬度观测到的间冰期高峰条件的延迟。此外，我们考虑了一个理想的126 ka融水情景，其中淡水输入是根据北方夏季高日照交互计算的。与LIG后期（122 ka）相比，该模式模拟了LIG早期（126 ka）更冷、更新鲜的北大西洋表层水和更弱的大西洋翻转。这一结果表明，为了重现我们在LIG早期确定的气候模式，必须考虑日晒和冰盖融化。我们的模式数据比较也揭示了一些局限性，并强调了使用耦合气候-冰盖模式和瞬态模拟进行进一步详细调查的必要性。
Although the Last Interglacial (LIG) is often considered as a possible analogue for future climate in high latitudes, its precise climate evolution and associated causes remain uncertain. Here we compile high-resolution marine sediment records from the North Atlantic, Labrador Sea, Norwegian Sea and the Southern Ocean. We document a delay in the establishment of peak interglacial conditions in the North Atlantic, Labrador and Norwegian Seas as compared to the Southern Ocean. In particular, we observe a persistent iceberg melting at high northern latitudes at the beginning of the LIG. It is associated with (1) colder and fresher surface-water conditions in the North Atlantic, Labrador and Norwegian Seas, and (2) a weaker ventilation of North Atlantic deep waters during the early LIG (129-125 ka) compared to the late LIG. Results from an ocean-atmosphere coupled model with insolation as a sole forcing for three key periods of the LIG show warmer North Atlantic surface waters and stronger Atlantic overturning during the early LIG (126 ka) than the late LIG (122 ka). Hence, insolation variations alone do not explain the delay in peak interglacial conditions observed at high northern latitudes. Additionally, we consider an idealized meltwater scenario at 126 ka where the freshwater input is interactively computed in response to the high boreal summer insolation. The model simulates colder, fresher North Atlantic surface waters and weaker Atlantic overturning during the early LIG (126 ka) compared to the late LIG (122 ka). This result suggests that both insolation and ice sheet melting have to be considered to reproduce the climatic pattern that we identify during the early LIG. Our model-data comparison also reveals a number of limitations and reinforces the need for further detailed investigations using coupled climate-ice sheet models and transient simulations.