Inconsistent Subsurface and Deeper Ocean Warming Signals During Recent Global Warming and Hiatus

Abstract

Ocean heat content (OHC) evolutions calculated from the data sets (WOA, MyOcean, ORAS4, and SODA) were examined at different depth ranges in this study. According to the OHC changes, the subsurface and deeper ocean (SDO, 300–2000 m) heat content rapidly increased over the world's ocean basins during 1998–2013, indicating significant warming in the SDO during the recent global surface warming hiatus. Almost all the ocean basins warmed up, but with various contributions to the global SDO warming tied to the recent hiatus. The role of the Indian Ocean is particularly important as it has accounted for about 30% of global SDO heat uptake during the hiatus. The combined use of multiple data sets can reveal inconsistencies in SDO warming analysis results, and improve our understanding of the role of the SDO in the recent hiatus. The heat uptake in global SDO during the hiatus was about 2.37, 5.44, 3.75, and 2.44 × 1022 joules with trends of 0.40, 0.70, 0.77, and 0.48 W m−2 according to WOA, MyOcean, ORAS4, and SODA respectively, presenting obviously inconsistent SDO warming signals. MyOcean shows OHC overestimates in different ocean basins, while ORAS4 presents more reliable SDO OHC analysis. In general, the global SDO has sequestered a significant amount of heat—about 3.50 × 1022 joules with trends of 0.59 W m−2 on average among the four data sets—during the recent hiatus, demonstrating widespread and significant warming signals in the global SDO. There remain substantial uncertainties and discrepancies, however (especially in the PO and SO), in the available SDO warming information due to insufficient subsurface observation coverage and variations in the data set generation techniques used among different researchers.

Retrieving Ocean Subsurface Temperature Using a Satellite‐Based Geographically Weighted Regression Model

“…During the warming hiatus (Kosaka & Xie, ), IO heat content has increased abruptly, and the IO has become more important in modulating global climate variability (Lee et al, ). Moreover, recent studies suggest that there is significant warming in the SDO of the IO; its role is particularly important in the global SDO warming during its recent hiatus (Su et al, ).…”

“…Heat uptake and redistribution within the oceans has led to recent global warming hiatus trends (Chen & Tung, ; Drijfhout et al, ; Yan et al, ). To mitigate the uncertainty of the SDO warming evaluation requires more accurate subsurface observation data (Su et al, ). Satellite observations cannot directly detect and provide subsurface thermal information, but they can be employed to obtain subsurface information based on special models (Li et al, ; Su et al, ).…”

Retrieving Temperature Anomaly in the Global Subsurface and Deeper Ocean From Satellite Observations

“…The recent hiatus (Kosaka & Xie, ) has been proven to be a heat redistribution within the oceans (Yan et al, ). The global subsurface and deeper ocean has played an essential role in the hiatus by heat uptake and storage (Chen & Tung, ; Drijfhout et al, ), but there is large uncertainty and discrepancy in the subsurface and deeper ocean warming evaluation (Su et al, ). Further understanding of the ocean heat redistribution could help better track the energy budget in the Earth's system (Yan et al, ), but requires long‐term, global‐scale ocean interior observation data.…”

Estimating Subsurface Thermohaline Structure of the Global Ocean Using Surface Remote Sensing Observations

“…Numerous studies have suggested that most of the heat gained by the Earth system is stored in the ocean, which leads to significant global ocean warming [3]. In particular, the heat variation and redistribution in the global subsurface and deeper ocean (300-2000 m) is of great significance to global climate change [4][5][6][7], but there are large uncertainties and discrepancies in the deeper ocean warming evaluation [8]. The ocean thermohaline structure as the indispensable environmental factors can be used to study ocean processes and climate change.…”

“…Current internal ocean observation data, while precise, are sparse in time and space and far from meeting observational requirements for multi-scale ocean process studies [8,10]. At the same time, the profile data of temperature and salinity in the ocean are sparse and their observations are extremely uneven, hindering our understanding of important dynamic processes within the ocean.…”