Transport of terrestrially derived nutrients along the Western Antarctic Peninsula, Anvers Island
David Reide Corbett, East Carolina University, Department of Coastal Studies, Greenville, NC, United States, Jared Crenshaw, East Carolina University, Greenville, NC, United States and Kimberly A Null, Moss Landing Marine Laboratories, Moss Landing, CA, United States
Abstract:
The surface waters of the Southern Ocean play a key role in global climate and carbon cycles with some of the world’s largest phytoplankton blooms. Several studies have emphasized the importance of glacial and sediment inputs of Fe that likely fuel the primary production of the Fe-limited Southern Ocean. Although the fertile surface waters along the shelf of the Western Antarctic Peninsula (WAP) are influenced by large inputs of freshwater, this freshwater may take multiple pathways (e.g. calving, streams, groundwater discharge) with different degrees of water/rock interactions leading to variable Fe flux to coastal waters. Here, we evaluate the shore-normal mixing rate of nearshore waters to evaluate the potential transport of nutrients, derived from an unevaluated source (i.e., submarine groundwater discharge), offshore along the WAP. Stable (i.e.,
2H,
18O) and radioactive (i.e.,
223,224,226,228Ra,
222Rn) tracers were used to evaluate the potential transport of these nutrients across the shelf. During the austral summers of 2012-2013 and 2013-2014, seawater samples were collected along the WAP, near Anvers Island, aboard the
R/V Laurence M. Gould to observe water-column and tracer dynamics in nearshore and offshore.
Porewaters collected near Palmer Station were found to be elevated in short-lived Ra isotopes and 222Rn, demonstrating that these tracers are valuable to delineating terrestrially-derived water masses as has been reported in temperate and tropical shelf systems. Using the full suite of tracers, comparisons of freshwater delivery to coastal waters are compared across seasons, with increased freshwater observed during the late austral summer, 2014. Horizontal mixing rates of water masses along the WAP ranged from 570 to 6820 m2 s-1. Fluorescence was elevated in several nearshore locations and found to be coincident with the high tracer activities used in this study to evaluate the distribution of terrestrial meltwater, suggesting the importance of glacial melt as a source of bio-limiting nutrients.
