Detecting Regional Deep Ocean Warming below 2000 meter Based on Altimetry, GRACE, Argo, and CTD Data

Abstract

The deep ocean below 2000 m is a large water body with the sparsest data coverage, challenging the closure of the sea-level budget and the estimation of the Earth’s energy imbalance. Whether the deep ocean below 2000 m is warming globally has been debated in the recent decade. However, as the regional signals are generally larger than the global average, it is intriguing to investigate the regional temperature changes. Here, we adopt an indirect method that combines altimetry, GRACE, and Argo data to examine the global and regional deep ocean temperature changes below 2000 m. The consistency between high-quality conductivity-temperature-depth (CTD) data from repeated hydrographic sections and our results confirms the validity of the indirect method. We find that the deep oceans are warming in the Middle East Indian Ocean, the subtropical North and Southwest Pacific, and the Northeast Atlantic, but cooling in the Northwest Atlantic and Southern oceans from 2005 to 2015.

摘要

近几十年来, 海洋加速变暖对地球气候系统和人类生活已经产生了重大影响. 由于深海直接观测资料的不足, 人类对于海洋冷暖的认识一般局限于海洋上层 2000 m. 海洋吸收的多余热量是否传递到了深海, 一直是全球变化领域最具挑战性的科学问题之一. 本文结合卫星测高、 卫星重力和海洋温盐数据间接的研究了全球和区域深海冷暖变化, 发现了 2005–15 年印度洋中东部、 亚热带西南太平洋和东北大西洋深海变暖, 而西北大西洋和南大洋深海变冷, 并利用全球海洋船载水文调查计划 (GO-SHIP) 的深海温盐观测数据验证了研究结果的可靠性. 由于这两种方法的时空分辨率存在较大差异, 间接估算的区域比容趋势值均大于 GO-SHIP 的 CTD 的观测结果. 因此, 间接法可用于定性地探测深海冷暖变化, 但仍难以准确量化深海的温度和热含量变化.