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

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 shore-normal mixing rate of nearshore waters using naturally-occurring radioactive isotopes. This mixing could transport nutrients derived from an unevaluated source (i.e., submarine groundwater discharge; SGD) offshore along the WAP. Stable isotopes of water (i.e., ²H, ¹�O) and radioactive groundwater tracers (i.e., ²²³,²²�,²²�,²²�Ra, ²²²Rn) were used to evaluate the potential source of these nutrients and nearshore water masses. 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 horizontal mixing of water across the continental shelf. Short- and long lived radium (Ra) isotopes and radon-222 (²²²Rn) are used to evaluate the rates that water masses mix 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 as has been reported in temperate and tropical shelf systems. 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, 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 within glacial fjords along the WAP ranged from 570 to 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 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.M.S

Nearshore mixing and nutrient delivery along the western Antarctic Peninsula

The surface waters of the Southern Ocean play a key role in the global climate and carbon cycles by promoting growth of some of the world’s largest phytoplankton blooms. Several studies have emphasized the importance of glacial and sediment inputs of Fe that 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 summers of 2012–13 and 2013–14, seawater samples were collected along the WAP, near Anvers Island, to observe water column dynamics in nearshore and offshore waters. Tracers (223,224Ra, 222Rn, 18O, 2H) were used to evaluate the source and transport of water and nutrients in coastal fjords and across the shelf. Coastal waters are compared across two field seasons, with increased freshwater observed during 2014. Horizontal mixing rates of water masses along the WAP ranged from 110–3600 m2 s-1. These mixing rates suggest a rapid transport mechanism for moving meltwater offshore.ECU Open Access Publishing Support Fun

Groundwater discharge to the western Antarctic coastal ocean

Submarine groundwater discharge (SGD) measurements have been limited along the Antarctic coast, although groundwater discharge is becoming recognized as an important process in the Antarctic. Quantifying this meltwater path-way is important for hydrologic budgets, ice mass balances and solute delivery to the coastal ocean. Here, we estimate the combined discharge of subglacial and submarine groundwater to the Antarctic coastal ocean. SGD, including subglacial and submarine groundwater, is quantified along the WAP at the Marr Glacier terminus using the activities of naturally occurring radium isotopes (223Ra, 224Ra). Estimated SGD fluxes from a 224Ra mass balance ranged from (0.41 ± 0.14)×104 and (8.2 ± 2.3)×104m3 d−1. Using a salinity mass balance, we estimate SGD contributes up to 32% of the total freshwater to the coastal environment near Palmer Station. This study suggests that a large portion of the melting glacier may be infiltrating into the bedrock and being discharged to coastal waters along the WAP. Meltwater infiltrating as groundwater at glacier termini is an import-ant solute delivery mechanism to the nearshore environment that can influence biological productivity. More importantly, quantifying this meltwater pathway may be worthy of attention when predicting future impacts of climate change on retreat of tidewater glaciers

zCall: a rare variant caller for array-based genotyping

Summary: zCall is a variant caller specifically designed for calling rare single-nucleotide polymorphisms from array-based technology. This caller is implemented as a post-processing step after a default calling algorithm has been applied. The algorithm uses the intensity profile of the common allele homozygote cluster to define the location of the other two genotype clusters. We demonstrate improved detection of rare alleles when applying zCall to samples that have both Illumina Infinium HumanExome BeadChip and exome sequencing data available

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

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 shore-normal mixing rate of nearshore waters using naturally-occurring radioactive isotopes. This mixing could transport nutrients derived from an unevaluated source (i.e., submarine groundwater discharge\; SGD) offshore along the WAP. Stable isotopes of water (i.e., ²H, ¹8O) and radioactive groundwater tracers (i.e., ²²³,²²4,²²6,²²8Ra, ²²²Rn) were used to evaluate the potential source of these nutrients and nearshore water masses. 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 horizontal mixing of water across the continental shelf. Short- and long lived radium (Ra) isotopes and radon-222 (²²²Rn) are used to evaluate the rates that water masses mix 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 as has been reported in temperate and tropical shelf systems. 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, 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 within glacial fjords along the WAP ranged from 570 to 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 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

Nearshore mixing and nutrient delivery along the western Antarctic Peninsula

The surface waters of the Southern Ocean play a key role in the global climate and carbon cycles bypromoting growth of some of the world"s largest phytoplankton blooms. Several studies have emphasized theimportance of glacial and sediment inputs of Fe that fuel the primary production of the Fe-limited SouthernOcean. Although the fertile surface waters along the shelf of the western Antarctic Peninsula (WAP) areinfluenced 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 coastalwaters. During the summers of 2012--13 and 2013--14, seawater samples were collected along the WAP, nearAnvers Island, to observe water column dynamics in nearshore and offshore waters. Tracers (223,224Ra,222Rn, 18O, 2H) were used to evaluate the source and transport of water and nutrients in coastal fjords andacross the shelf. Coastal waters are compared across two field seasons, with increased freshwater observed 2 -1during2014.HorizontalmixingratesofwatermassesalongtheWAPrangedfrom110--3600m s .These mixing rates suggest a rapid transport mechanism for moving meltwater offshore

Groundwater discharge to the western Antarctic coastal ocean

Submarine groundwater discharge (SGD) measurements have been limited along the Antarctic coast, although groundwater discharge is becoming recognized as an important process in the Antarctic. Quantifying this meltwater path-way is important for hydrologic budgets, ice mass balances and solute delivery to the coastal ocean. Here, we estimate the combined discharge of subglacial and submarine groundwater to the Antarctic coastal ocean. SGD, including subglacial and submarine groundwater, is quantified along the WAP at the Marr Glacier terminus using the activities of naturally occurring radium isotopes (223Ra, 224Ra). Estimated SGD fluxes from a 224Ra mass balance ranged from (0.41 ± 0.14)×104 and (8.2 ± 2.3)×104m3 d−1. Using a salinity mass balance, we estimate SGD contributes up to 32% of the total freshwater to the coastal environment near Palmer Station. This study suggests that a large portion of the melting glacier may be infiltrating into the bedrock and being discharged to coastal waters along the WAP. Meltwater infiltrating as groundwater at glacier termini is an import-ant solute delivery mechanism to the nearshore environment that can influence biological productivity. More importantly, quantifying this meltwater pathway may be worthy of attention when predicting future impacts of climate change on retreat of tidewater glaciers

zCall: a rare variant caller for array-based genotyping

Summary: zCall is a variant caller specifically designed for calling rare single-nucleotide polymorphisms from array-based technology. This caller is implemented as a post-processing step after a default calling algorithm has been applied. The algorithm uses the intensity profile of the common allele homozygote cluster to define the location of the other two genotype clusters. We demonstrate improved detection of rare alleles when applying zCall to samples that have both Illumina Infinium HumanExome BeadChip and exome sequencing data available. Availability: http://atguweb.mgh.harvard.edu/apps/zcall. Contact: [email protected] Supplementary Information: Supplementary data are available at Bioinformatics online