Water mass structure and the effect of subglacial discharge in Bowdoin Fjord, northwestern Greenland

• Main Authors: Ohashi, Yoshihiko, Aoki, Shigeru, Matsumura, Yoshimasa, Sugiyama, Shin, Kanna, Naoya, Sakakibara, Daiki
• Format: Text
• Language: English
• Published: 2019
• Subjects: Bowdoin; Bowdoin Fjord; Greenland
• Online Access: https://doi.org/10.5194/os-2019-33; https://www.ocean-sci-discuss.net/os-2019-33/

Subglacial discharge has significant impacts on water circulation, material transport, and biological productivity in proglacial fjords of Greenland. To help clarify the fjord water properties and the effect of subglacial discharge, we investigated the water mass structures of Bowdoin Fjord in northwestern Greenland based on summer hydrographic observations, including turbidity, in 2014 and 2016. We estimated the fraction of subglacial discharge from the observational data and interpreted the observed differences in subglacial discharge behavior between two summer seasons with the numerical model results. At a depth of 60–80 m, temperature profiles were distinctively different in 2014 and 2016, and a larger fraction of submarine meltwater was detected in 2014. At a depth of 15–40 m, where the most turbid water was observed, the maximum subglacial discharge fractions near the ice front were estimated to be ~ 6 % in 2014 and ~ 4 % in 2016. The higher discharge fraction in 2014 was due to the stronger stratification, as suggested by numerical experiments performed with different initial stratifications. Turbidity near the surface was higher in 2016 than in 2014, suggesting a stronger influence of turbid subglacial discharge. The higher turbidity in 2016 could primarily be attributed to a greater amount of subglacial discharge, as inferred from the numerical experiments forced by different amounts of discharge. This study indicates that ambient fjord stratification difference is an important factor controlling the vertical distribution of subglacial discharge, together with its amount.