A new study reveals just how efficiently the ocean managed to store heat during the last deglaciation, shedding light on significant implications of these findings for our understanding and future of the climate system.
The Modern Paradox of Ocean Warming
In the modern age, >90% of extra heat under way because of anthropogenic environmental change has been taken up by t he sea. Yet this warming has mostly been confined to the upper 500 meters of the ocean, and is relatively weak in the deep ocean.
This results in a rather low value of ocean heat storage efficiency equal to 0.1 (which implied that 10 % of the added heat accumulation is truly realized). This has been a mystery for climate scientists, because the deep ocean is supposed to be the final resting place of 90% of the extra heat from global warming.
The Revelations from the Past
However, paleoceanographic observations paint a different picture. Such observations imply that on millennial and longer time scales, such as during the last deglaciation, deep ocean warming might be nearly as globally significant as surface ocean warming.
The result is of particular interest as it suggests that the thermal efficiency of ocean heat storage during the last deglaciation — and conceivably at other times in Earth history — was about ten times greater than modern values, attaining efficiency greater than or equal to 1. Then the question becomes: what process(es) was(were) responsible for this strong ocean heat uptake and storage, and how do we assess their application to the future?
Conclusion
These findings have important implications for our understanding of the climate in a broad sense, as well as ocean heat uptake and the biases introduced by other systematic noise in observations. This new information as to how oceans warmed may help us in constraining the response of climate to changes in carbon dioxide levels and refining our predictions for future patterns of warming across the globe. Based on these results, the oceanic dynamical responses to multiple forcing factors remain a plausible route for a well-rounded comprehension of past, current and future pathways in Earth’s climate.
