Deep Chlorophyll as a Tracer of Winter Carbon Export at the Hatteras Front

Abstract: Cape Hatteras, NC, USA, is a region known to be a hotspot for the offshore export of shelf waters, but the effect of that export on biogeochemical processes in this region is less well understood. This is a region where Mid-Atlantic Bight (MAB), South Atlantic Bight (SAB), and Gulf Stream (GS) waters with very different biogeochemical properties converge (Figure 1). Furthermore, recent work from the `Processes Driving Exchange At Cape Hatteras’ (PEACH) program has shown evidence that shelf water export is dominated by episodic events. Biogeochemical interactions and exchange during these events are likely to have important implications for the carbon budget on the shelf. In this study, we analyze high spatial and temporal resolution chlorophyll and oxygen data collected by Spray gliders deployed during PEACH over a 2-year period, from March 2017 to May 2019. We examine seasonal patterns in the distribution of chlorophyll in the water column and within different water masses. Additionally, we examine finer scale variability in chlorophyll associated with frontal structures and how they associate with temperature and salinity to determine that specific cases of deep chlorophyll are likely due subduction events.