Abstract
AbstractThe World Ocean is estimated to store more than 90% of the excess energy resulting from man-made greenhouse gas–driven radiative forcing as heat. Uncertainties of this estimate are related to undersampling of the subpolar and polar regions and of the depths below 2000 m. Here we present measurements from the Weddell Sea that cover the whole water column down to the sea floor, taken by the same accurate method at locations revisited every few years since 1989. Our results show widespread warming with similar long-term temperature trends below 700-m depth at all sampling sites. The mean heating rate below 2000 m exceeds that of the global ocean by a factor of about 5. Salinity tends to increase—in contrast to other Southern Ocean regions—at most sites and depths below 700 m, but nowhere strongly enough to fully compensate for the warming effect on seawater density, which hence shows a general decrease. In the top 700 m neither temperature nor salinity shows clear trends. A closer look at the vertical distribution of changes along an approximately zonal and a meridional section across the Weddell Gyre reveals that the strongest vertically coherent warming is observed at the flanks of the gyre over the deep continental slopes and at its northern edge where the gyre connects to the Antarctic Circumpolar Current (ACC). Most likely, the warming of the interior Weddell Sea is driven by changes of the Weddell Gyre strength and its interaction with the ACC.
Highlights
Assessing the heat budget of planet Earth is an essential prerequisite for verifying the concept of anthropogenic global warming and the models describing this (e.g., Hansen et al 2011; Palmer 2012; Trenberth and Fasullo 2012; von Schuckmann et al 2016)
The trends were determined by linear regression, which explains between 20% and 92% of the variance
Based on the justified assumption of spatially uniform warming of each layer, we calculated the heat content change and the heating rate of each volume according to Eqs. (1) and (2)
Summary
Assessing the heat budget of planet Earth is an essential prerequisite for verifying the concept of anthropogenic global warming and the models describing this (e.g., Hansen et al 2011; Palmer 2012; Trenberth and Fasullo 2012; von Schuckmann et al 2016). When Earth surface temperature measurements indicated a stalled rise of global mean temperature, while atmospheric CO2 concentrations continued to increase during the 15-yr period following the 1998 El Niño, the paradigm of anthropogenic global warming was challenged. Since 2012 global mean surface temperatures, picked up rising and have reached new record highs (e.g., https://crudata.uea.ac.uk/cru/data/temperature/; GISTEMP Team 2020; Lenssen et al 2019; NOAA 2020; Zhang et al 2019). The 1998–2012 slowdown of surface temperature increase, often termed the ‘‘global warming hiatus,’’ and its ending are widely explained and mostly attributed to variable distributions of heat between the surface of the ocean and its deep interior (Kosaka and Xie 2013; Chen and Tung 2014; Lee et al 2015; Fyfe et al 2016)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
