Meridional transport in the Indian Ocean traced by coral radiocarbon

Ocean circulation in the Indian Ocean is predominantly driven by the monsoon and is responsible for convergence along the equator. As a result, upwelling is primarily restricted to the western boundary where surface waters are anomalously depleted in 14C. Here, we describe aspects of western boundary upwelling based on insights derived from the first coral radiocarbon time-series in the Indian Ocean. The absence of a distinct subannual pre-bomb Δ14C signal suggests that open and coastal upwelling are negligible off the coast of Kenya. Instead, our results suggest that upwelling from the coast of Somalia and possibly Oman are the sources of the depleted seasonal Δ14C signal. In contrast, the southern hemisphere subtropical gyre provides water enriched in 14C. We demonstrate that the coral Δ14C time-series is a tracer for meridional transport in the Indian Ocean. The Indian Ocean exhibits a shallow cross-equatorial overturning circulation cell. Our results demonstrate that the Kenyan coral radiocarbon record is responding to a western boundary limb of this cell, similar to that observed in other subtropical oceans. Therefore, while the majority of cross-equatorial transport is in the interior and eastern basin of the Indian Ocean, our results argue that the Somali Current is a distinct pathway for inter-hemispheric water mass exchange

Preservation of glaciochemical time-series in snow and ice from the Penny Ice Cap, Baffin Island

A detailed investigation of major ion concentrations of snow and ice in the summit region of Penny Ice Cap (PIC) was performed to determine the effects of summer melt on the glaciochemical time-series. While ion migration due to meltwater percolation makes it difficult to confidently count annual layers in the glaciochemical profiles, time-series of these parameters do show good structure and a strong one year spectral component, suggesting that annual to biannual signals are preserved in PIC glaciochemical records

Pre-Bomb Radiocarbon Variability Inferred from a Kenyan Coral Record

We report results from AMS radiocarbon measurements (Delta-14C) in corals recovered off the coast of Kenya. Bimonthly samples which span the pre-bomb era average -51 per mil (+/3.7; n=43), when age and Suess effect are corrected, and over the time of interest (1946-1954) do not exhibit any discernible seasonality. Relative to regional pre-bomb Delta-14C values in the western Indian Ocean, our results indicate 14C enrichment off the coast of Kenya. Furthermore, the absence of a distinct subannual Delta-14C signal suggests that open and coastal upwelling is negligible off the coast of Kenya. Unlike pre-bomb values south of the equator near Seychelles and Madagascar, our pre-bomb value are enriched by more than 10 per mil. The enrichment of pre-bomb Kenyan Delta-14C values relative to sites around Mauritius, northern Madagascar and Seychelles, suggest that the influence of depleted Delta-14C water transported in the SEC is limited to regions south of 3 to 4 degrees S.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202