Cruise Report RV Sanna, Cruise GLICE, 10.08.2022 – 24.10.2022, Ilulissat (Greenland) – Ilulissat (Greenland)

• Main Author: Hopwood, Mark J.
• Format: Report
• Language: English
• Published: 2022
• Subjects: Greenland; Ilulissat; Sanna; Disko Bay
• Online Access: https://oceanrep.geomar.de/id/eprint/57454/; https://oceanrep.geomar.de/id/eprint/57454/1/GLICE%20Cruise%20Report%20Hopwood%202022.pdf

GLICE embarked a team of scientists to study the effect of icebergs on pelagic processes in Disko Bay in August 2022, anticipated to be close to the peak of the annual melt season. A combination of underway measurements, profiles and opportunistic sampling around icebergs were used to increase understanding of how ice melt affects marine biogeochemistry. In addition to sensor-based salinity, temperature, chlorophyll and turbidity measurements, our team focused on carbonate chemistry (direct measurements of pCO2, pH and total alkalinity, TA), macronutrients (nitrate, phosphate, silicic acid – with a subset of samples analysed for silicic acid at sea) and acoustic Doppler current profiler (ADCP) data acquisition. Our sampling focused mainly on the upper 100 m where the strongest gradients in parameters that may respond directly to ice melt were expected and we mainly employed a statistical approach to dataset collection, focusing the majority of the cruise on sampling pre-defined transects in a grid across the Bay area intercepting areas with high and low ice/melt water distributions. This can be combined with satellite based observations to understand iceberg dynamics. Process studies were also conducted, tracking 3 large icebergs with concentric data collection within their vicinities to investigate the possibility of small scale responses to iceberg passage, incubating ambient seawater with additions of iceberg melt and/or sediment, and using repeat sampling of ‘line F’ in front of the Ilulissat Icefjord entrance to constrain short-term (diel) dynamics.