Highlights

Coccolithophores, unicellular calcifying phytoplankton, grow in a region spanning the entire Southern Ocean termed the “Great Calcite Belt” (GCB). Particulate inorganic carbon (PIC) is generated through the process of coccolithophore calcification, and the GCB is thought to host over a quarter of globally suspended PIC. Sensitive to changes in temperature and ocean alkalinity, coccolithophore growth and hence the GCB are likely to be influenced by climate change, but the drivers of the emergence of the GCB are not yet well understood. Leveraging a marine ecosystem model coupled to an earth system model that reproduces realistic spatial distributions of Southern Ocean PIC, we diagnosed the bottom-up (light, nutrients, and temperature) and top-down (mortality, aggregation, and zooplankton grazing) controls on Southern Ocean coccolithophore growth, with the aim at understanding the controls on GCB spatial extent and magnitude, and found that temperature is the largest constraint on coccolithophore extent, and that iron controls…

In our new paper “Environmental Drivers of Coccolithophore Growth in the Pacific Sector of the Southern Ocean” we use both observations (shipboard and remote sensing) in combinations with simple growth models (parameterized using CESM/MARBL) to understand what are the major driving factors controlling calcification in the Subantarctic Zone, particularly far from any sedimentary sources. This work was done in collaboration with Dennis McGillicuddy, Kristen Krumhardt, Matt C. Long, Nick Bates, Bruce Bowler, Dave Drapeau, and Barney Balch. Please feel free to email me for a copy of the paper should you need access.

Much of Greenland runoff is delivered to the coastal ocean at marine-terminating glaciers, potentially hundreds of meters below the sea surface. The resulting turbulent buoyant plumes can entrain nurtrient-rich deeper waters, potentially delivering these nutrients to the upper water column which can support elevated primary productivity. The importance of this buoyant plume-productivity effect around Greenland is not yet clear, however. Here, we apply buoyant plume theory on a pan-Greenland scale to assess the potential for subglacial-discharge driven nutrient enhancements between glacier termini, and find that most of the upwelling is concentrated in a few hotspots, with 14% of glaciers driving >50% of the total nitrate effect. We then compare the model results to coastal chlorphyll concentrations, and find strong interannual relationships are limited to CW and NW Greenland. Subglacial discharge fluxes can explain most of the interannual variability in seasonal chlorophyll in northern Disko Bay and Uummannaq Fjord, which host…

Our new SPIROPA paper led by Gordon Zhang on cross-shelf tracer exchange by a streamer of shelf water on the eastern periphery of a warm-core ring in the Middle Atlantic Bight has been published in Progress in Oceanography! Find the paper here: https://doi.org/10.1016/j.pocean.2022.102931

Check out our new paper characterizing buoyant plume dynamics across Greenland, led by Donald Slater “Characteristic depths, fluxes, and timescales for Greenland’s tidewater glacier fjords from subglacial discharge-driven upwelling during summer”. Watch Donald’s IGS seminar on this work here. (Article PDF)  

Our new SPIROPA paper is now out in JGR: “Ephemeral surface chlorophyll enhancement at the New England shelf break driven by Ekman restratification”.