Seasonal observations of stable isotope variations in a valleycatchment, Signy Island, South Orkney Islands

[摘要] The oxygen and hydrogen isotope composition of waters in a small valley at Signy Island, SouthOrkney Islands, were monitored over three summers (1999 to 2001). These stable isotopes track watermovement through the catchment, especially seasonal precipitation and snow melt. All samples fall close tothe regional meteoric water line but factors other than air temperature cause year-to-year variability.Residence times are in the order of days thus the lake water provides an average of precipitation falling onlya few days before, except in the winter when the lakes are effectively closed. Freezing of surface waterspreserves the isotope signature of the underlying waters from the previous summer. In spring, meltwatersfrom winter snow are isotopically depleted having δ18O and δD as low as -13‰ and -100‰ (VSMOW). Ice-cover break-up in late December allows complete water column mixing. By February, the lakes arerelatively enriched isotopically (δ18O -9‰) by summer precipitation. Precipitation isotopic composition atHalley Station, Brunt Ice Shelf, is similar, illustrating the broad-scale effects of the Weddell Sea cyclonicatmospheric circulation. These data form a useful reference data-set for the ground-based validation ofatmospheric models and palaeoclimate reconstructions in this isolated sector of the South Atlantic Ocean.

[学科分类] 自然科学（综合）