The Role of African Dust in Atlantic Climate During Heinrich Events

L. Murphy, Marlos Goes, A. Clement
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引用次数: 3

Abstract

Increased ice discharge in the North Atlantic is thought to cause a weakening, or collapse, of the Atlantic meridional overturning circulation (AMOC) during Heinrich events. Paleoclimate records indicate that these periods were marked by severe tropical aridity and dustiness. Although the driver of these events is still under debate, large freshwater input is necessary for climate models to simulate the magnitude, geographical extent, and abruptness of these events, indicating that they may be missing feedbacks. We hypothesize that the dust-climate feedback is one such feedback that has not been previously considered. Here we analyze the role of dust-climate feedbacks on the AMOC by parameterizing the dust radiative effects in an intermediate complexity model and consider uncertainties due to wind stress forcing and the magnitude of both atmospheric dust loading and freshwater hosing. We simulate both stable and unstable AMOC regimes by changing the prescribed wind stress forcing. In the unstable regime, additional dust loading during Heinrich events cools and freshens the North Atlantic and abruptly reduces the AMOC by 20% relative to a control simulation. In the stable regime, however, additional dust forcing alone does not alter the AMOC strength. Including both freshwater and dust forcing results in a cooling of the subtropical North Atlantic more comparable to proxy records than with freshwater forcing alone. We conclude that dust-climate feedbacks may provide amplification to Heinrich cooling by further weakening AMOC and increasing North Atlantic sea ice coverage.
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海因里希事件期间非洲沙尘在大西洋气候中的作用
北大西洋冰流量的增加被认为会导致海因里希事件期间大西洋经向翻转环流(AMOC)的减弱或崩溃。古气候记录表明,这些时期以严重的热带干旱和多尘为特征。尽管这些事件的驱动因素仍在争论中,但气候模型需要大量淡水输入来模拟这些事件的规模、地理范围和突发性,这表明它们可能缺少反馈。我们假设沙尘气候反馈是一种以前没有考虑过的反馈。在这里,我们通过在中等复杂度模型中参数化灰尘辐射效应来分析灰尘气候反馈对AMOC的作用,并考虑由于风应力强迫以及大气灰尘负荷和淡水冲刷的大小而产生的不确定性。我们通过改变规定的风应力来模拟稳定和不稳定的AMOC状态。在不稳定状态下,海因里希事件期间的额外灰尘负荷使北大西洋降温和清新,并使AMOC相对于对照模拟突然降低20%。然而,在稳定状态下,额外的尘埃作用力本身不会改变AMOC强度。包括淡水和沙尘强迫在内,副热带北大西洋的降温与代理记录相比,更具可比性。我们得出的结论是,沙尘气候反馈可能通过进一步削弱AMOC和增加北大西洋海冰覆盖率来放大海因里希冷却。
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来源期刊
Paleoceanography
Paleoceanography 地学-地球科学综合
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6-12 weeks
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