Research published recently in PNAS attempts to shed light on the gaps in scientific knowledge regarding ocean warming. The team of scientists behind the study reconstructed the history of ocean warming and determined evidence to support previous studies that say that the oceans are absorbing over 90% of human-emitted greenhouse gases.
The estimates published in the study state that the ocean began warming decades ago, has absorbed 436 x 1021 Joules from 1871 to present. That quantity accounts for approximately 1000 times the annual worldwide human primary energy consumption. Science Daily also reports that warming was similar throughout the time periods of 1920-1945 and 1990-2015.
The biggest conclusion coming from the study suggests that ocean circulation is the cause of up to half the observed warming and associated sea level rise in low- and mid- latitudes of the Atlantic Ocean in the last 60 years. “During this period, more heat has accumulated at lower latitudes than would have if circulation were not changing,” reports Science Daily.
Professor Samar Khatiwala explained the researchers’ method to measure ocean absorption of human-emitted carbon dioxide: “Our approach is akin to "painting" different bits of the ocean surface with dyes of different colors and monitoring how they spread into the interior over time. We can then apply that information to anything else -- for example humanmade carbon or heat anomalies -- that is transported by ocean circulation. If we know what the sea surface temperature anomaly was in 1870 in the North Atlantic Ocean we can figure out how much it contributes to the warming in, say, the deep Indian Ocean in 2018. The idea goes back nearly 200 years to the English mathematician George Green.”
Although this method still lacks validation and it only applies to humanmade greenhouse gases that are passively transported by ocean circulation, it has produced out relatively consistent results. Another researcher on the study, Professor Zanna, commented that the researchers “were pleasantly surprised how well the approach works,” adding, “It opens up an exciting new way to study ocean warming in addition to using direct measurements.”