Eddie Gonzales Jr. – MessageToEagle.com – The global ocean, a major heat reservoir, absorbs over 90% of excess energy from anthropogenic warming.
In the last century, significant ocean warming has occurred in the upper 500 m, with weaker warming in the deep ocean and a small heat storage efficiency of 0. 1.
Melting ice in the Southern Ocean. Image credit: Jiuxin Shi
Paleoceanographic observations suggest that over long periods, deep ocean warming can equal or exceed surface ocean warming. Ocean heat storage efficiency during the last deglaciation was about ten times its modern value.
This raises the following question: what mechanisms are responsible for ocean heat uptake/storage and how large can its efficiency be?
Now, an international team of scientists from China and USA has shed light on this issue. By combining state-of-the-art deglacial simulations and proxy-based reconstructions, they resolved the three-dimensional deglacial ocean temperature change . They found that the deglacial ocean heat storage efficiency is substantially enhanced to =1 by strong warming in intermediate-depth waters in response to deglacial forcing.
“Our simulations and proxy reconstructions demonstrate that the three-dimensional ocean warming during the last deglaciation was strongly nonuniform with strongest warming occurring at intermediate depths, in striking contrast to contemporary observations,” said Dr. Chenyu Zhu from Institute of Atmospheric Sciences at the Chinese Academy of Sciences, the study’s co-first author.
Utilizing sensitivity experiments, the study revealed that the large warming of intermediate waters can be related to surface warming at mid-to-subpolar latitudes through ventilation in response to greenhouse gases and ice sheet forcing and substantially enhanced by oceanic circulation change associated with meltwater forcing. “
The unique ocean warming structure facilitates a large ocean heat storage efficiency. In particular, this resolves the paradox suggested by the conventional view that warming occurred at sites of deep-water formation that remained covered by sea ice”, said Prof. Zhengyu Liu, one of the corresponding authors of the study from The Ohio State University.
“These results have valuable implications. For example, if strong surface warming and strong ventilation are collocated like in our simulations, then the ocean will absorb more heat from the atmosphere, potentially slowing the rate of atmospheric warming” said Prof. Peter U. Clark, another corresponding author of the study from Oregon State University.
The study underscores the important role of surface warming pattern and oceanic circulation change in long-term ocean heat storage change and suggests that “the ocean can serve as a far greater reservoir of energy in the climate system than implied by contemporary observations,” according to the study.
Original press release – Institute of Atmospheric Physics Chinese Academy of Sciences via Eurekalert
Written by Eddie Gonzales Jr. – MessageToEagle.com Staff Writer