The Oceans Heat Up As Global Warming Persists

An analysis of three independent datasets confirm that the oceans are warming rapidly.

AsianScientist (July 18, 2017) – Scientists have confirmed that oceans around the world are feeling the heat in a study published in the journal Climate Dynamics.

More than 90 percent of the earth’s energy imbalance in the climate system is absorbed by the ocean. Consequently, the ocean heat content (OHC) is increasing—a clear indication of global warming.

During the past 30 years, many independent groups have worked to estimate historical OHC changes. However, not all researchers agree on the published global OHC time series. For example, different scientific studies on the so-called ‘hiatus’ or ‘slowdown’ period from 1998 to 2012 draw quite different conclusions. Consensus has not been found on key scientific questions such as: Where is the heat redistributed in the ocean? Which ocean basin dominates the change in global OHC?

In this study, three different ocean datasets—the Ishii Dataset from Japan, the EN4 dataset from the Meteorological Office in the UK, and the Institute of Atmospheric Physics (IAP) dataset from China—were objectively analyzed. The change in OHC on decadal (ten years) and multi-decadal scales and at different ocean basins was also thoroughly examined.

The analysis results revealed that the oceans are indeed warming, regardless of which dataset was used. In addition, the heat among global oceans experienced a significant redistribution in the past several decades.

Importantly, this study helps account for the differences in the datasets examined. The researchers point out discrepancies in the depth ranges used in calculating OHC as well as the uncertainty in subsurface temperature datasets which could have affected the conclusions drawn from the datasets.

The Ishii analysis also underestimated the heating rate in the southern hemisphere in the past century, while the EN4 analysis could not correctly reconstruct the sea surface temperature (SST) during the past 30 years and underestimated the warming rate by approximately 90 percent compared with other independent SST datasets.

“In plain English, it is important that we keep high-quality temperature sensors positioned throughout the oceans so in the future we will be able to predict where our climate is headed,” explained Professor John P. Abraham from the University of St. Thomas, US, who co-authored the paper with PhD student Wang Gongjie from the National University of Defence Technology, China.

“We say in science that a measurement not made is a measurement lost forever. And measurements of the heating of the oceans are of utmost importance,” Abraham added.

The article can be found at: Wang et al. (2017) Consensuses and Discrepancies of Basin-scale Ocean Heat Content Changes in Different Ocean Analyses.


Copyright: Asian Scientist Magazine; Photo: Alexander Cobb/Singapore-MIT Alliance for Research and Technology.
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