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Creators/Authors contains: "Amos, Caitlin M."

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  1. Abstract

    The Greenland ice sheet is melting at increasing rates. Changes in freshwater input to the Labrador Sea can influence coastal circulation and biological processes, stratification, and potentially winter convection. Many recent studies have investigated freshwater variability in the region based on model simulations or observations with limited spatial/temporal coverage. Here, we use in situ (1990–2019) and satellite (2011–2017) observations of surface salinity to characterize freshwater content and to identify transport pathways in the Labrador Sea over multiple years. Large freshening is observed in coastal waters off southwest Greenland from July to November. Interannual variability in freshening near the coast seems to be at least partially related to variability in meltwater input, although the sparseness of in situ data precludes a quantitative assessment. The seasonal westward transport of freshwater is enhanced between 60°–62°N and especially between 63°–64.8°N from August to October, with the low‐salinity waters circumnavigating the basin following the 1,000–2,000 m isobaths. That pathway coincides with intensifications in the component of the surface geostrophic flow that is directed offshore, highlighting the role played by the large‐scale circulation on the westward transport of the freshwater. Low‐salinity water can be transported toward the central Labrador Sea at synoptic scales, however, where it can potentially influence stratification. Consistent with previous modeling studies, offshore freshening is reduced in years with persistent downwelling‐favorable wind conditions. Despite limitations under cold water conditions, satellite observations of surface salinity compare well with in situ data suggesting that they can be useful for monitoring freshwater content in high latitudes.

     
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  2. Abstract

    The California Current System is characterized by upwelling and rich mesoscale eddy activity. Cyclonic eddies generally pinch off from meanders in the California Current, potentially trapping upwelled water along the coast and transporting it offshore. Here, we use satellite-derived measurements of particulate organic carbon (POC) as a tracer of coastal water to show that cyclones located offshore that were generated near the coast contain higher carbon concentrations in their interior than cyclones of the same amplitude generated offshore. This indicates that eddies are in fact trapping and transporting coastal water offshore, resulting in an offshore POC enrichment of 20.9 ± 11 Gg year−1. This POC enrichment due to the coastally-generated eddies extends for 1000 km from shore. This analysis provides large-scale observational-based evidence that eddies play a quantitatively important role in the offshore transport of coastal water, substantially widening the area influenced by highly productive upwelled waters in the California Current System.

     
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  3. Abstract

    The Southern Ocean is characterized by high eddy activity and high particulate organic carbon (POC) content during summer, especially near Antarctica. Because it encircles the globe, it provides a pathway for inter‐basin exchange. Here, we use satellite observations and a high‐resolution ocean model to quantify offshore transport of coastal water rich in POC off the West Antarctic Peninsula. We show that nonlinear cyclonic eddies generated near the coast often trap coastal water rich in POC during formation before propagating offshore. As a result, cyclones found offshore that were generated near the coast have on average higher POC content in their interior than cyclones generated locally offshore. This results in a POC enrichment of 5.7 ± 3.0 Gg C year−1in offshore waters off the Peninsula. Actual POC enrichment is likely substantially larger, since about half of the volume transport of coastal water is driven by small eddies that are missed by observations.

     
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