Search for: All records

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. 

Abstract Few observational platforms are able to sustain direct measurements of all the key variables needed in the bulk calculation of air‐sea carbon dioxide (CO₂) exchange, a capability newly established for some Uncrewed Surface Vehicles (USVs). Western boundary currents are particularly challenging observational regions due to strong variability and dangerous sea states but are also known hot spots for CO₂uptake, making air‐sea exchange quantification in this region both difficult and important. Here, we present new observations collected by Saildrone USVs in the Gulf Stream during the winters of 2019 and 2022. We compared Saildrone data across co‐located vehicles and against the Pioneer Array moorings to validate the data quality. We explored how CO₂flux estimates differ when all variables needed to calculate fluxes from the bulk formulas are simultaneously measured on the same platform, relative to the situation where in situ observations must be combined with publicly‐available data products. We systematically replaced variables in the bulk formula with those often used for local and regional flux estimates. The analysis revealed that when using the ERA‐5 reanalysis wind speed in place of in situ observations, the ocean uptake of CO₂is underestimated by 8%; this underestimate grows to 9% if the NOAA Marine Boundary Layer atmospheric CO₂product and ERA‐5 significant wave height are also used in place of in situ observations. Overall our findings point to the importance of collecting contemporaneous observations of wind speed and oceanpCO₂to reduce biases in estimates of regional CO₂flux, especially during high wind events.