Deep Argo Quantifies Bottom Water Warming Rates in the Southwest Pacific Basin

Gregory C Johnson1, Sarah G Purkey2, Nathalie V Zilberman2 and Dean H Roemmich2, (1)NOAA Pacific Marine Environmental Laboratory, Seattle, WA, United States, (2)Scripps Institution of Oceanography UCSD, La Jolla, CA, United States
Data reported from mid 2014 through late 2018 by a regional pilot array of Deep Argo floats in the Southwest Pacific Basin are used to estimate regional temperature anomalies from a long-term climatology as well as regional trends over the 4.4 years of float data as a function of pressure. The data show warm anomalies that increase with increasing pressure from effectively 0 near 2000 dbar to over 10 (±1) m°C by 4800 dbar, uncertainties estimated at 5–95%. The 4.4-year trend estimate shows warming at an average rate of 3 (±1) m°C yr-1 from 5000–5600 dbar, in the near-homogeneous layer of cold, dense, bottom water of Antarctic origin. These results suggest acceleration of previously reported long-term warming trends in the abyssal waters in this region. They also demonstrate the ability of Deep Argo to quantify changes in the deep ocean in near-real-time over short periods with high accuracy