Diurnal chemistry of two contrasting stream types, Taylor Valley, McMurdo Dry Valley Region, Antarctica

Russell S Harmon,W Berry Lyons,Kathleen A Welch,Deborah L Leslie,Diane M Mcknight

doi:10.1051/e3sconf/20199801020

Abstract

Numerous ephemeral streams flow within the McMurdo Dry Valley Region of Antarctica that transport glacial meltwater to perennially ice-covered, closed-basin lakes during the austral summer. The diurnal behavior for two Taylor Valley streams of different character was examined during the summer of 2010-11. Andersen Creek is a short, 1st-order proglacial stream, whereas Von Guerard Stream is a long, high-order stream with an extensive hyporheic zone that has a substantial cyanobacterial algal mat community in its middle reaches. Both streams display strong daily cycles for temperature, electrical conductivity, dissolved oxygen, and pH. Conductivity varies in concert with flow, with solute dilution occurring during the daily high-flow pulse. Dissolved oxygen co-varies strongly with pH at Andersen Creek but not for Von Guerard Stream. Each stream has a distinct geochemical character that for Andersen Creek is a direct reflection of its glacial source, unmodified by secondary effects, whereas that for Von Guerard Stream is modulated by its resident algal mat community and through extensive hyporheic zone interaction and exchange.

Highlights

Introduction and backgroundLocated in the central Transantarctic Mountains between the East Antarctic Ice Sheet and the Ross Sea coast of Victoria Land in Antarctica (Fig. 1A), the McMurdo Dry Valley region (MDVR) is the largest ice-free area of Antarctica
Time-series sampling at ~5-minute intervals was undertaken at Von Guerard Stream (VGS) for 4215 minutes from 1700 on 31 December 2010 to 1520 on 3 January 2011 and at Andersen Creek (AC) for 5600 minutes from 1700 on 3 January to 1415 on 7 January 2011 during the summer period of main stream flow when glacial melting is maximal and stream hyporheic zones are fully developed
The relative compositional consistency of VGS over the entirety of a summer flow season reflects compositional modulation by its extensive mid-reach hyporheic zone, where water in transient storage introduced during times of high stream flow has an extended opportunity for water-sediment interaction and pore-water exchange before a portion returns to the main stream channel during the daily low-flow interval

Summary

Introduction

Introduction and backgroundLocated in the central Transantarctic Mountains between the East Antarctic Ice Sheet and the Ross Sea coast of Victoria Land in Antarctica (Fig. 1A), the McMurdo Dry Valley region (MDVR) is the largest ice-free area of Antarctica. The chemistry of AC, with its minimal hyporheic zone, more closely reflects the composition and high variability of its glacial source waters and displays the long-term geochemical fingerprint Alk>Ca>Cl>Na>SO4>Mg>K>Si [9] that is biased towards Cl and SO4, such that Cl can even be elevated over Ca during high-flow intervals.

Results

Conclusion