Oxygen isotope studies from Iceland to an East Greenland Fjord: behaviour of glacial meltwater plume

Abstract

A detailed study of the oxygen isotope composition (δ18O) was carried out along a transect between Iceland and East Greenland, which includes the West Iceland Shelf, Denmark Strait, the Kangerdlugssuaq Trough on the East Greenland Shelf and the Kangerdlugssuaq Fjord. Vertical profiles of the oxygen isotope composition in a fjord with tidewater glaciers were studied for the first time. In this study, three distinct water masses are identified from oxygen isotope measurements: (1) North Atlantic Water of δ18O ≈ 0%. occupies the Icelandic Shelf, Denmark Strait subsurface, and deep waters of the Kangerdlugssuaq Trough and Fjord; (2) the East Greenland Current of δ18O ≈ −2%. occupies surface water at the western Denmark Strait and the Kangerdlugssuaq Trough; (3) glacial meltwater (δ18O ranges from −30 to −20%. in source) flows at the surface of the Kangerdlugssuaq Fjord. Surface δ18O data distinctively identify the East Greenland Front between North Atlantic Water and the East Greenland Current in Denmark Strait. Vertical profiles of δ18O show the steady increase from surface to deep water at the stations west of the front with well mixed water at stations east of the front. We did not find any subsurface glacial meltwater intrusion in Kangerdlugssuaq fjord, unlike the reported ‘cold tongue’ in Antarctic fjords. Instead Arctic Intermediate Water (winter cooled North Atlantic Water) penetrates to the head of the fjord and fills the bottom part of the fjord. A linear relationship between salinity and δ18O shows that there was no significant contribution from the sea ice meltwater in this study site. The dominant source of freshwater in the Kangerdlugssuaq Fjord is glacial meltwater. A simple model using δ18O was developed to illustrate glacial meltwater dynamics in the fjord, and to estimate the length of the glacial meltwater plume. Model results agree well with the data within the fjord and near the fjord mouth and a plume length is estimated to be 250 km from the glacial face. However, a diversion of the model from the data is observed at about 70 km away from the mouth of the fjord because of the influence by the East Greenland Current and the Coriolis effect.