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North Atlantic Ocean yields clues for better weather predictions

North Atlantic Ocean yields clues for better weather predictions

Research links to federal priority on progress in Earth system predictability

By Randy Showstack | September 18, 2020

The ability to forecast atmospheric blocking could improve predictions of melting and the acceleration of ice loss in Greenland. “If we know how blocking is going to change, and why it changes, that can help us to better understand why and when Greenland is going to melt,” says WHOI physical oceanographer Young-Oh Kwon.  (Photo by Fiamma Straneo © Woods Hole Oceanographic Institution)

When Young-Oh Kwon was a graduate student in physical oceanography about 20 years ago, scientists knew a fair amount about how the atmosphere influences the ocean, and many felt that ocean variability doesn’t affect the atmosphere in a meaningful way outside of the tropics.

“Our knowledge of the interaction”—between the ocean and the atmosphere—“was mostly one way,” says Kwon, a senior scientist in WHOI’s Department of Physical Oceanography.

However, with more accurate models, high resolution satellite data, and a better understanding of ocean-atmosphere interactions, that knowledge has vastly improved. A June paper that Kwon coauthored shows that “atmospheric blocking,” over the North Atlantic, a weather phenomenon that stalls the normal progression of weather, can be predicted due to its relationship to the ocean, and natural variability in the North Atlantic.

“Detecting decadal predictability for components of the atmospheric circulation is remarkable and opens the door to new possibilities,” the paper states.

While we usually don’t have predictability for the weather system longer than two weeks or so, Kwon says this paper shows that it’s possible to make decadal predictions.

This finding “will lead to more attention to how the ocean can be an important source of predictability in weather and climate,” says Kwon. Although the current study predicted retrospective conditions, he says that a future goal would be to use that predictability in forecasts that can benefit society.

The ability to forecast atmospheric blocking could have far-reaching implications for predicting its impact on elements of the Earth system such agriculture, sea ice, fisheries, and long-range weather.  One impact, for instance, is how blocking can affect ocean circulation that in turn affects marine ecosystems and fisheries such as cod fisheries in the Nordic Sea.

Another impact is on ice melt in Greenland. Atmospheric blocking above Greenland usually brings warmer temperatures that are favorable to Greenland ice melt. “If we know how blocking is going to change, and why it changes, that can help us to better understand why and when Greenland is going to melt,” according to Kwon.

WHOI physical oceanographer Young-Oh Kwon. (Photo by Daniel Hentz, © Woods Hole Oceanographic Institution)

That predictive capability, which has implications for science and for people’s lives, ties right in with an August 2019 White House memorandum on Fiscal Year 2021 administration research and development budget priorities.It recognizes the importance of Earth system predictability “from individual thunderstorms to long-term global change,” and states that federal “departments and agencies should prioritize R&D that helps quantify Earth system predictability across multiple phenomena, time, and space scales.”

While the Earth science community has been discussing Earth system predictability for the past decade or so, Kwon says that he was pleasantly surprised by the White House memo and that the new research “falls right in the heart of that recommendation that we need to understand the predictability of the Earth system."

That memorandum led to a follow-up June virtual workshop on Earth system predictability research and development held by the National Academies of Sciences, Engineering, and Medicine.

Kwon and his colleagues used climate models from the Community Earth System Model (CESM) Decadal Prediction large Ensemble (DPLE), developed and housed at the National Center for Atmospheric Science (NCAS), to test out how well the models are able to predict atmospheric blocking.

The research, which notes that there are other mechanisms—including those in the stratosphere—that also might influence atmospheric blocking, builds upon earlier studies. These include a paper published in February 2020 that first  identified the ocean’s impact on the atmospheric blocking and a 2011 paper about atmospheric blocking and Atlantic multidecadal ocean variability.

Grateful for the recent White House memorandum, Kwon says, “this is an exciting time to study Earth system predictability, not just scientifically, but also from the policy side. The capacity to predict the Earth system and what is going to happen on the timescale of a few years will help us plan our future better.”

Funding for Kwon’s research was supported by the DOE (Regional and Global Model Analysis Program), NSF (Climate Large-Scale Dynamics Program), NASA (Physical Oceanography Program), and NOAA (Climate Variability and Predictability Program).