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Influence of African dust on ocean - Atmosphere variability in the tropical Atlantic

机译:非洲尘埃对热带大西洋海洋-大气变化的影响。

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摘要

The dominant source of coupled ocean - atmosphere variability in the tropical Atlantic is the so-called Atlantic Meridional Mode~(1-3). This mode of variability is characterized by an interhemispheric gradient in sea surface temperatures and by oscillations in the strength of surface winds that cross the Equator, thereby reinforcing sea surface temperature anomalies ~(1-4). The Atlantic Meridional Mode is thermodynamically damped and must receive external forcing to persist as observed~3. However, it is not known which external forcing factors have excited the Atlantic Meridional Mode in the historical record. Here we present simulations with an ocean general circulation model that is forced by a record of surface radiation from anomalous dust concentrations in the atmosphere, reconstructed from a coral proxy and satellite retrievals. We show that the Atlantic Meridional Mode is excited by variability in African dust outbreaks on interannual to decadal timescales. Our analysis indicates that sea surface temperature anomalies resulting from the aerosol direct effect persist in time through the positive ocean - atmosphere feedback~5 that defines the Atlantic Meridional Mode. We conclude that on interannual to decadal timescales, the state of the tropical Atlantic ocean is directly tied to dust emissions over West Africa, which in turn are linked to land-use change~(6-8).
机译:热带大西洋中海洋与大气耦合的主要来源是所谓的大西洋子午线模式(1-3)。这种变化方式的特征是海面温度呈半球状梯度变化,并以横越赤道的海面风的强度振荡为特征,从而加剧了海面温度异常〜(1-4)。大西洋子午线模式具有热力学阻尼性,必须接受外部强迫才能如3所示持续存在。但是,在历史记录中还不清楚哪些外部强迫因素激发了大西洋子午线模式。在这里,我们通过海洋总环流模型进行模拟,该模型是由大气中异常尘埃浓度引起的表面辐射记录推动的,该记录是通过珊瑚代理和卫星检索重建的。我们显示,大西洋经线模式对非洲尘埃暴发的年际至年代际尺度的变化感到兴奋。我们的分析表明,由气溶胶直接作用引起的海面温度异常在整个正海洋中一直持续存在,大气反馈〜5定义了大西洋子午线模式。我们得出的结论是,在每年到十年的时间尺度上,热带大西洋的状态直接与西非的粉尘排放有关,而粉尘的排放又与土地利用的变化有关(6-8)。

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