The efficiency of the biological carbon pump in the ocean and its response to continuously warming temperatures are of great importance to future projections of global change. Here, we investigate a time series of organic carbon fluxes from a monthly resolved sediment trap mooring in the Gulf of Aqaba (GOA), northern Red Sea, between 2014 and 2016. We evaluate the attenuation of sinking organic carbon in the context of the seasonally changing euphotic zone and provide the first estimates of biological pump efficiency in this region. The base of the euphotic zone changed seasonally as the system transitioned from oligotrophic and stratified conditions in summer to mesotrophic conditions during the winter mixing period. Carbon attenuation assessed using a power law fit yields an average coefficient of b = 0.80 ± 0.37, lower than expected based on the warm temperatures in the GOA. Estimates of export efficiency decreased from 40% in summer to 20% in winter, and show the opposite seasonal pattern as transfer efficiencies, which increased from 50% in summer to 95% in winter. Overall, the efficiency of the carbon pump was close to 20% in both seasons. These observations challenge the notion of a globally uniform positive correlation between increasing temperature and increasing carbon attenuation in the ocean and imply that warm subtropical ecosystems can support moderately enhanced carbon pump efficiencies, possibly also related to increased, dust-driven, mineral ballasting in low latitude regions such as the GOA

Primary Presenter: Stephanie Kienast, Dalhousie University (stephanie.kienast@dal.ca)

Authors:

Adi Torfstein, The Hebrew University of Jerusalem  (adi.torf@mail.huji.ac.il)