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The Caribbean Through-Flow (CTF) is a critical chokepoint for North and South Atlantic waters that form the North Atlantic western boundary current system and the upper ocean limb of the Atlantic Meridional Overturning Circulation. While the circulation and energetics of the CTF have been well studied, its water mass transformations remain poorly constrained. Using over 7700 Argo float profiles from 2014 to 2024, we document a prominent westward modification in water mass structure across the Caribbean Sea. From the eastern to western Caribbean, we observe systematic increases in ocean heat content, a deepening of isopycnals, and a freshening and deepening of the subsurface salinity maximum. These changes result in a net mid-depth (~50–500 m) density reduction of 0.40 ± 0.27 kg m-3. We hypothesize that regional variations in mesoscale eddy activity, complex bathymetry, and meridional wind stress curl gradients drive this transformation. The resulting water mass structure has critical implications for regional climate, weather, ecosystems, and sea level rise, as it modifies the density and stratification of source waters entering the Gulf of Mexico and North Atlantic western boundary current system. Our findings highlight the importance of internal Caribbean processes in shaping upper-ocean heat and salt transport in the Atlantic and underscore the need for sustained in situ observations in the region and targeted modeling analyses of the underlying modification processes.
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This content will become publicly available on December 1, 2026
Warming and salinity changes of the upper ocean Caribbean through-flow since 1960
The Caribbean through-flow (CTF) is a vital component of Earth’s climate system, facilitating and impacted by heat and salt fluxes from major circulation systems like the North Atlantic Subtropical Gyre (NASTG) and Atlantic Meridional Overturning Circulation (AMOC). Here, we show significant changes have occurred in upper ocean water mass properties of the CTF since 1960, including subsurface warming of ~ 0.2 °C decade−1, surface freshening of ~ 0.13 g kg−1 decade−1, and subsurface salinification of ~ 0.05 g kg−1 decade−1. In the upper 0–200 m, temperature and stability increases are nearly 3 and 20 times larger than globally averaged trends, respectively, with implications for tropical cyclones, sea level rise, and marine ecosystems. We show these upper ocean changes are likely impacting water mass formation in the NASTG, thereby indirectly influencing the AMOC. These findings highlight the CTF as a bottleneck for climatically important water masses and emphasize the need for sustained subsurface observations here.
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- PAR ID:
- 10627713
- Publisher / Repository:
- https://www.nature.com/articles/s41598-025-05494-z#citeas
- Date Published:
- Journal Name:
- Scientific Reports
- Volume:
- 15
- Issue:
- 1
- ISSN:
- 2045-2322
- Subject(s) / Keyword(s):
- Caribbean Through-Flow Ocean Circulation North Atlantic Subtropical Gyre Atlantic Meridional Overturning Circulation
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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