Precession modulates the poleward expansion of atmospheric circulation to the Arctic Ocean

Arctic climate is projected to become more sensitive to changes in North Pacific meridional heat transport under global warming. This is postulated as a consequence of low-high latitude teleconnections, but the exact underlying mechanisms remain poorly understood. Here, we reconstruct subarctic humidity changes over the past 400 kyr to investigate the role of low-high latitude interactions in regulating Arctic hydroclimate. Our reconstruction is based on precipitation-driven sediment input variations in the Subarctic North Pacific (SANP), which reveal a strong precessional cycle in the subarctic humidity under the relatively low eccentricity conditions that prevailed over the past four glacial cycles. Combined with new model simulations, we demonstrate that the observed cyclic hydroclimate changes can be attributed to meridional shifts in the northern rim of the subtropical ocean gyre through affecting water vapor transfer efficiency to the SANP. Our findings support projections of a northward shift of the North Pacific polar gyre in response to future global warming, which will lead to increasingly wet conditions in addition to sea-ice losses in the Arctic Ocean.

全球变暖背景下，北极气候预计将对北太平洋经向热输送的变化变得更为敏感。这被认为是低纬-高纬遥相关（teleconnections）的结果，但确切的潜在机制仍知之甚少。在此，我们重建了过去40万年亚北极的湿度变化，以探究低纬-高纬相互作用在调控北极水文气候中的作用。我们的重建基于亚北极北太平洋（SANP）降水驱动的沉积物输入变化，该变化揭示了过去四个冰期旋回中相对低偏心率条件下亚北极湿度存在强烈的岁差周期。结合新的模型模拟，我们证明观测到的水文气候周期性变化可归因于副热带海洋环流北缘的经向移动，其通过影响向SANP的水汽传输效率发挥作用。我们的研究结果支持了未来全球变暖下北太平洋极地环流北移的预测，这将导致北冰洋除海冰消融外，还出现日益湿润的状况。