Summary: | [1] A highly resolved Mt. Everest ice core reveals a decrease in marine and increase in continental air masses related to relatively high summer surface pressure over Mongolia, and reduction in northward incursions of the summer South Asian monsoon since 1400 AD. Previously published proxy records from lower sites south of the Himalayas indicate strengthening of the monsoon since this time. These regional differences are consistent with a south– north seesaw in convective activity in the Asian monsoon region, and reflect a southward shift in the mean summer position of themonsoon trough since1400AD. The change in monsoonal circulation at 1400 AD is synchronous with a
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