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Ocean radiocarbon (14C) is a proxy for air-sea exchange, vertical and horizontal mixing, and water mass identification. Here, we present five pre- to post-bomb coral Δ14C records from West Flower Garden Bank and Santiaguillo reefs in the Gulf of Mexico, Boca de Medio, and Isla Tortuga near the Cariaco Basin north of Venezuela. To assess basin-wide Δ14C variability, we compiled the Atlantic Ocean reef-building surface coral Δ14C records (24 corals and 28 data sets in total) with these new records. Cumulatively, the Δ14C records, on their independent age models, reveal the onset of post-bomb Δ14C trends in 1958 ±1 to 2 years. A general decrease in maximum Δ14C values occurs with decreasing latitude, reflecting the balance between air-sea gas exchange and surface water residence time, vertical mixing, and horizontal advection. A slightly larger atmospheric imprint in the northern sites and relatively greater vertical mixing and/or advection of low-14C waters influence the southern Caribbean and eastern Atlantic sites. The eastern Atlantic sites, due to upwelling, have the lowest post-bomb Δ14C values. Equatorial currents from the eastern Atlantic transport low Δ14C water towards the western South Atlantic and southern Caribbean sites. Decadal Δ14C averages for the pre-bomb interval (1750–1949) for the low latitude western Atlantic are relatively constant within analytical (3–5‰) and chronological uncertainties (~1–2 years) due to mixing and air-sea exchange. The compiled Δ14C records provide updated regional marine Δ14C values for marine reservoir corrections.
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Intrusions of Amazon River Waters in the Virgin Islands Basin During 2007–2017
Abstract The Virgin Islands basin (VIB) includes several Marine Protected Areas (MPAs) of interest as biologically unique spawning aggregation sites. The ecological structure in and around these MPAs is regulated by several factors, including changes in near‐surface water properties. Anomalously low near‐surface salinity is observed in the VIB during April 2009/2011, and March 2010, with a salinity signature consistent with Amazon plume waters. Other low salinity events in the region are found during 2007–2017 using output from an ocean reanalysis. The reanalysis shows that horizontal salinity advection explains near‐surface salinity variability in the VIB to a high degree, including events observed in the in situ measurements. We use a Lagrangian Particle tracking model to track particles over the 2007–2017 period and identify the source and pathways of water imports to the VIB. We describe three pathways. The northernmost one is often associated with advection of salty Atlantic waters. The two southernmost paths are associated with advection of low salinity waters from the Amazon into the VIB. The latter two pathways arrive to the Caribbean Sea as described in previous studies on low salinity advection to the wider Caribbean from the Amazon River; we find that once in the Caribbean Sea, the low salinity water makes its way into the VIB when steered northward by mesoscale features. This results in Amazon River waters regulating salinity variability in the VIB during April–November. During December–March, when mesoscale activity is at its minimum, the Atlantic inflow regulates the salinity variability within the VIB instead.
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- Award ID(s):
- 2026954
- PAR ID:
- 10400640
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Oceans
- Volume:
- 128
- Issue:
- 3
- ISSN:
- 2169-9275
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Ocean radiocarbon (14C) is a proxy for air-sea exchange, vertical and horizontal mixing, and water mass identification. Here, we present five pre- to post-bomb coral Δ14C records from West Flower Garden Bank and Santiaguillo reefs in the Gulf of Mexico, Boca de Medio, and Isla Tortuga near the Cariaco Basin north of Venezuela. To assess basin-wide Δ14C variability, we compiled the Atlantic Ocean reef-building surface coral Δ14C records (24 corals and 28 data sets in total) with these new records. Cumulatively, the Δ14C records, on their independent age models, reveal the onset of post-bomb Δ14C trends in 1958 ±1 to 2 years. A general decrease in maximum Δ14C values occurs with decreasing latitude, reflecting the balance between air-sea gas exchange and surface water residence time, vertical mixing, and horizontal advection. A slightly larger atmospheric imprint in the northern sites and relatively greater vertical mixing and/or advection of low-14C waters influence the southern Caribbean and eastern Atlantic sites. The eastern Atlantic sites, due to upwelling, have the lowest post-bomb Δ14C values. Equatorial currents from the eastern Atlantic transport low Δ14C water towards the western South Atlantic and southern Caribbean sites. Decadal Δ14C averages for the pre-bomb interval (1750–1949) for the low latitude western Atlantic are relatively constant within analytical (3–5‰) and chronological uncertainties (∼1–2 years) due to mixing and air-sea exchange. The compiled Δ14C records provide updated regional marine Δ14C values for marine reservoir corrections.more » « less
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