School of Geography, Geology and the Environment, University of Leicester, University Rd, Leicester, LE1 7RH, UK.
Molecular and Life Sciences, Curtin University, Kent St, Bentley, Perth, WA, 6102, Australia.
Sci Rep. 2021 Oct 14;11(1):20395. doi: 10.1038/s41598-021-99738-3.
Small changes in Pacific temperature gradients connected with the El Niño Southern Oscillation (ENSO) influence the Walker Circulation and are related to global climate anomalies. Therefore, it is of paramount importance to develop robust indices of their past behavior. Here, we reconstruct the difference in sea surface temperature between the west and central Pacific during ENSO, coined the West Pacific Gradient (WPG), based on the Last Millennium Paleo Hydrodynamics Data Assimilation. We show that the WPG tracks ENSO variability and strongly co-varies with the zonal gradient in Pacific sea surface temperature. We demonstrate that the WPG strength is related to significant atmospheric circulation and precipitation anomalies during historical El Niño and La Niña events by magnifying or weakening droughts and pluvials across the Indo-Pacific. We show that an extreme negative WPG coupled to a strong zonal Pacific temperature gradient is associated with enhanced megadroughts in North America between 1400 CE and the late sixteenth century. The twentieth century stands out in showing the most extreme swings between positive and negative WPG conditions over the past Millennium. We conclude that the WPG is a robust index together with ENSO indices to reveal past changes in Pacific zonal sea surface temperature gradient variability.
太平洋温度梯度的微小变化与厄尔尼诺南方涛动（ENSO）有关，这些变化会影响沃克环流，并与全球气候异常有关。因此，开发过去行为的稳健指标至关重要。在这里，我们基于上千年古气候动力数据同化，重建了 ENSO 期间西太平洋和中太平洋海面温度之间的差异，称之为西太平洋梯度（WPG）。我们表明，WPG 跟踪 ENSO 变化，并且与太平洋海面温度的纬向梯度强烈共变。我们证明，WPG 强度与历史上厄尔尼诺和拉尼娜事件期间的显著大气环流和降水异常有关，通过放大或减弱印度洋-太平洋地区的干旱和丰水期。我们表明，在 1400 年至 16 世纪后期的北美，与强烈的纬向太平洋温度梯度相关的极端负 WPG 与增强的特大干旱有关。20 世纪在过去一千年中表现出最极端的正 WPG 和负 WPG 条件之间的波动。我们得出结论，WPG 是一个稳健的指标，与 ENSO 指数一起揭示太平洋纬向海面温度梯度变化的过去变化。
