Maps showing the composite average of “open” and “closed valve” conditions for the Labrador Current.
Composite average of “open” (left column) and “closed valve” (right column) conditions for the Labrador Current, respectively. The top raw panels show potential thickness of the lower layer through which the Labrador Current penetrates, showing the ticker and thinner lower layer in “open” and “closed valve” condition caused by less and more warm core eddies in the upper layer, respectively. The middle raw panels show the average salinity. More westward freshwater expansion due to the Labrador Current penetration can be seen in “open valve” condition. The bottom panels show averaged current velocity; westward currents are absent in “closed valve” condition. Credit: Neto et al. [2023], Figure 9
Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Journal of Geophysical Research: Oceans

Although recent studies report that the Northwestern Atlantic Shelf is the fastest warming region of the ocean, detailed mechanisms of the warming have been unclear. By releasing numerous passive particles on the density surfaces in the Labrador Current (reproduced by an eddy resolving ocean model), Neto et al. [2023] found that warm core rings emanating from the Gulf Stream prevent the Labrador Current from penetrating westward onto the Northwestern Atlantic Shelf, causing the warming. Long-term analyses further revealed that this blockage has been seen more frequently since 2008, leading to a rapid warming of the shelf waters.

Lesser penetration of the Labrador Current may have implications for weakening of the large-scale ocean circulations, known as the Atlantic Meridional Overturning Circulation. Further, the warming caused by blocking the Labrador Current may cause marine heat waves and drastically change the local environment, challenging the ecosystem and fisheries management.

Citation: Neto, A. G., Palter, J. B., Xu, X., & Fratantoni, P. (2023). Temporal variability of the Labrador Current pathways around the Tail of the Grand Banks at intermediate depths in a high-resolution ocean circulation model. Journal of Geophysical Research: Oceans, 128, e2022JC018756.

—Takeyoshi Nagai, Editor, JGR: Oceans

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