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Chemistry and stratification of Antarctic meltwater ponds II: Inland ponds in the McMurdo Dry Valleys, Victoria Land

Published online by Cambridge University Press:  14 November 2006

M. Healy
Affiliation:
Department of Geology, University of Auckland, Private Bag 92019, Auckland, New Zealand
J.G. Webster-Brown
Affiliation:
Environmental Science, SGES, University of Auckland, Private Bag 92019, Auckland, New Zealand
K.L. Brown
Affiliation:
Department of Geology, University of Auckland, Private Bag 92019, Auckland, New Zealand
V. Lane
Affiliation:
Environmental Science, SGES, University of Auckland, Private Bag 92019, Auckland, New Zealand

Abstract

Meltwater ponds in the Victoria Valley and in the Labyrinth at the head of the Wright Valley of Victoria Land were sampled in January (summer) and October (late winter) of 2004 to establish their geochemistry and stratification, and to compare this with that of coastal meltwater ponds at a similar latitude near Bratina Island. In summer, vertical profiles were measured in 14 ponds; 10 were thermally stratified (maximum ΔT = 11.5°C) and 12 demonstrated a conductivity increase (∼25x) in the lowest 10–20 cm of the water column. When 11 of these ponds were resampled in October, the ice columns were stratified with respect to conductivity and five ponds had highly saline (up to 148 mS cm−1), oxygenated basal brines present under the ice. Basal brines and summer melt waters were Na-Cl dominated, and Victoria Valley pond meltwaters were enriched in Ca relative to the Labyrinth ponds. Early gypsum precipitation directs the chemical evolution of residual brine during freezing. These ponds were enriched in NO3 relative to the coastal ponds at Bratina Island, due to dissolution of nitrate-bearing soil salts, and the reduced influence of marine aerosols and biological productivity on pond chemistry.

Type
Research Article
Copyright
Antarctic Science Ltd 2006

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