Degree

Doctor of Philosophy (PhD)

Department

Oceanography and Coastal Sciences

Document Type

Dissertation

Abstract

The biological carbon pump (BCP) plays an essential role in the ocean’s ability to sequester atmospheric CO2. The BCP transfers carbon from the surface ocean and sequester it in the deep ocean or sediments on timescales of hundreds to thousands of years. It has been shown that even 1% change in this export efficiency of carbon by BCP can result in up to 10% change in atmospheric CO2 level. The predicted changes in future climate can disproportionately impact the oxygen minimum zone, riverine discharge and sea-ice melting among other things, which will directly impact the magnitude and efficiency of the BCP in future, although the exact implications are currently unknown. This study focuses on better understanding and quantifying the carbon export in three contrasting regions of global ocean that are currently undergoing dramatic changes (iii) the continental margin of Peru (ii) continental slope of northern Gulf of Mexico (nGOM), (iii) the western Arctic Ocean.

In this work we utilize naturally occurring 238U-234Th and 210Pb-210Po radioisotope pairs as tracers of carbon export fluxes to quantify the magnitude and efficiency of BCP at the base of the euphotic zone on monthly to seasonal scale. The results indicate that carbon fluxes ranged from 22.7 ± 2.7 to 164.2 ± 7.9 mg C m-2 d-1 in Peruvian Coast, 8.6 - 37.6 mg C m-2 d-1 in nGOM and 0.75 - 7.23 mg C m-2 d-1 in Arctic Ocean. We observed a negative relationship between the magnitude and efficiency of BCP among these three regions, with lowest export but highest export efficiency in the Arctic Ocean followed by nGOM and the Peruvian Coast. In addition to POC export by the BCP, this study examined the role of particle composition on scavenging and sorption in the Arctic Ocean using 210Pb-210Po as tracers of terrigenous and bioactive elements. Our results suggest that particle composition alone cannot explain the observed variability in partition coefficient (Kd) across the different oceanic regime along the transect suggesting that higher particulate Mn concentration in the Arctic may be partly responsible for the higher Kd observed in the basin compared to Atlantic and Pacific.

Committee Chair

Maiti, Kanchan

Available for download on Sunday, March 05, 2028

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