Recent cooling in the lower Pacific Ocean based on dynamically-consistent ocean syntheses

Abstract

The thermal state from 1993–2017 in the lower Pacific Ocean (below 2 km) was investigated using two dynamically-consistent syntheses. We show a robust and bottom-intensified cooling. This Pacific cooling is mainly determined by the meridional heat exchange with the Southern Ocean and the vertical heat advection. The abyssal Pacific Ocean loses heat by way of westward heat advection in the northwest ocean. Mixing is found to play a negligible role. This study is to some extent consistent with a recent study that presented a deep Pacific cooling as an adjustment to the last Little Ice Age. However, it contradicts with most recent studies, which argued the abyssal Pacific Ocean was warming over the recent two decades. Our study suggests that special caution is needed when auditing variations in the deep ocean and more work is in need for a better understanding of the deep ocean state.