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 iron (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. During the austral summers of 2012-2013 and 2013-2014, seawater samples were collected along the WAP, near Anvers Island, to observe water-column and tracer dynamics in nearshore and offshore waters. Stable (²H, ¹⁸O) and radioactive (^223,224Ra, ²²²Rn) tracers were used to evaluate the transport of water and potential nutrients in glacial fjords and across the shelf. Using the full suite of tracers, coastal waters were compared across seasons, with increased freshwater observed during the late austral summer, 2014. Horizontal mixing rates of water masses along the WAP ranged from 110 to 3600 m² s^-1. These mixing rates are within the range of other rates calculated along the WAP and suggest a rapid transport mechanism for moving meltwater offshore.

Freshwater inputs to the Antarctic coastal ocean and transport across the continental shelf can occur through multiple pathways, all with different degrees of water/rock interactions. Until recently, submarine groundwater discharge had not been considered as an important physical process near the Antarctic continent and its effects on coastal polar ecosystems are poorly understood. Multiple tracers of freshwater and groundwater were used to capture geochemical changes and quantify freshwater inputs and constituent fluxes associated with different pathways including calving, streams, and groundwater discharge at a tidewater glacier near Anvers Island on the WAP (Figures 1 and 2). Primary production in iron-limited waters offshore of the Antarctic Peninsula is believed to be fueled by continentally-derived sediments among other sources and our work demonstrates that subglacial/submarine groundwater discharge is also an important source of dissolved iron, approximately 10 times that of calving, to coastal waters in this region (Figure 3).

This research combines multiple direct measurements with established tracer techniques to quantify submarine groundwater discharge (SGD) in the coastal zone along the Western Antarctic Peninsula and the transport of Fe and other constituents to the continental shelf. Temporal variations in SGD were evaluated during two summer field campaigns, with bi-weekly changes monitored. Direct measurements of meltwater show high tracers and macro-nutrient concentrations, indicating a significant source to surface waters. This project is the first to directly measure glacial meltwater discharge, including groundwater, and the associated major and minor nutrient concentrations to the coastal ocean.  The project has trained two masters’ students, mentored a post-doc, and provided significant oceanographic experience to 4 additional graduate students. Results have led to more than 10 scientific presentations (domestic and international), several outreach efforts with K-12 students, a completed MS thesis, a submitted manuscript to Science and Marine Chemistry, an accepted manuscript in Antarctic Science, and two additional to be submitted in the next couple months.

Last Modified: 09/02/2016
Modified by: David R Corbett