Mount Logan Ice Core Evidence for Changes in the Hadley and Walker Circulations Following the end of the Little Ice Age

Abstract

The Hadley and Walker circulations dominate the climate of the tropics and contribute to extratropical climate variability through the forcing of planetary waves that result in the long-range correlation of atmospheric circulation patterns known as teleconnections. Previous work showed that an annually resolved 301-year ice core record of annual snow accumulation from a high-elevation site on Mount Logan in northwestern North America contains an expression of one such teleconnection, the Pacific-North American (PNA) pattern. Here we show that this record contains a related signal associated with the regional Hadley and Walker circulations in the Pacific. We argue that the positive trend in snow accumulation in the ice core that started in the middle of the nineteenth century is a reflection of changes in the intensities of these circulations that has been ongoing since the end of the Little Ice Age (LIA).