Antarctic Bottom Water Warming in Eastern Pacific Southern Ocean*

Past research indicates that Antarctic Bottom Water has been warming in recent decades, both near its formation areas such as the Ross Sea, Weddell Sea, and Adélie Coast, and in more distant locations like much of the Pacific Ocean, the western South Atlantic Ocean, and portions of the Indian Ocean. Our study focused on the bottom water in the Eastern Pacific section of the Southern Ocean. From the 1990s through 2023 we found an average warming trend of 2.9 ± 0.4 m°C yr-1 at pressures exceeding 3500 dbar in this region. The data also suggests an accelerating warming trend over the past 30 years, with warming trends from the 2000s and 2010s through 2023 estimated as 4.4 ± 1.0 m°C yr-1 and 8.3 ± 2.2 m°C yr-1, respectively. Consistent with this increasing warming pattern, we observed an acceleration of the deepening of the coldest isotherms indicating an accelerated reduction in the inflow of the coldest waters in the bottom ocean.