Transport of terrestrially derived nutrients along the Western Antarctic Peninsula, Anvers Island.

摘要

The mechanisms that supply Fe to the surface waters off the coast of the Western Antarctic Peninsula (WAP) play a key role in the global climate cycle by fueling primary production in this vast and globally important environment. This study investigates the transport of nutrients to offshore waters along the WAP from a previously unevaluated source (submarine groundwater discharge; SGD) using a suite of naturally-occurring stable and radioactive isotopes that are indicative of SGD. During the austral summers of 2012-2013 and 2013-2014, seawater samples were collected along the WAP offshore of Anvers Island aboard the R/V Laurence M. Gould (LMG) to observe water-column and tracer dynamics in nearshore and offshore environments in order to evaluate the source and mixing of water across the continental shelf.;Short- and long lived radium (Ra) isotopes and radon-222 (222 Rn) are used to evaluate the rates at which water masses move in shelf waters. 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. Offshore surface waters were depleted in short-lived Ra isotopes and 222Rn relative to porewaters, and within the range of those measured in other regions of the WAP and temperate nearshore environments. Using the full suite of parameters measured, the sources of surface water masses along the shelf were determined. Transport rates of terrestrially derived water masses within glacial fjords along the WAP ranged 570-6820 m2s-1. Short-lived Ra isotopes were used to estimate the timing of the most recent sediment-water interaction in surface waters. Estimates ranged between 15-25 days offshore of Anvers Island. Fluorescence was elevated in several nearshore locations and found to be coincident with the tracers used in this study to evaluate the distribution of terrestrial meltwater, suggesting the importance of glacial melt as a source of bio-limiting nutrients.