Enhanced freshwater discharge and soil erosion/thawing in response to anthropogenic climate change leads to profound downstream perturbations in marine environments offshore Greenland, impacting light availability , water-column stratification, fjord-shelf exchange, seawater chemistry and nutrient inventories/biogeochemistry. Increased freshwater discharge is expected to be accompanied by rising nutrient supply potentially sustaining biological production and export, yet enhanced turbid river discharge may induce light limitation and strong near-surface stratification, thereby limiting biological production. The response of marine productivity to enhanced meltwater discharge is thus ultimately dependent on glacier type (marine- or land-terminating glaciers), fjord-glacier geometry, phytoplankton nutrient requirement and trophic interactions. Increased discharge thus bears important consequences on marine ecosystems/services including carbon sequestration and fisheries. The resulting overall disturbances to the taxonomy, phenology and productivity of Greenland’s marine ecosystems are likely leading to significant feedbacks on climate through associated changes in the air-sea exchange of climate-active gases as well as aerosol-forming substances like dimethylsulfide (DMS). However, the exact mechanisms and extent of such changes and feedbacks remain poorly constrained.
The ocean cluster will focus on quantifying (micro)nutrient and carbon fluxes (both in the dissolved and particulate phases) between the atmosphere, the cryosphere, soils and the ocean using constant flux tracers (230Th and/or 234Th) to derive vertical particle fluxes to the underlying sediments. Efforts will, in addition, focus on determining the provenance and chemical composition of meltwater and runoff using geochemical fingerprinting (water isotopes, REE, eNd, 232Th) as well as on constraining the link between fjord geometry, glacier dynamics and nutrient solubilization and transport. These factors ultimately modulate phytoplankton and microbial compositions as well as key aspects of the microbial loop, which control the cycling and transport of carbon and nutrients, with consequences for sedimentary carbon sequestration. Sinking particulate material will be characterized using organic and inorganic approaches, including biomarker composition, biomarker-specific isotopes (13C, 14C) and geochemical isotope fingerprinting (REE, eNd, 232Th). The connectivity between the surface ocean and the atmosphere will be documented by comparing surface water properties (chemical and biological compositions) along with air-sea CO2 and aerosol fluxes. The variability within different fjord systems will be monitored at high spatial resolution using semi-autonomous sensors (CTD, turbidity, nutrients, CDOM, fluorescence, PAR).
Cluster Project Investigator
Prof. Dr Samuel Jaccard, Marine Geology and Biogeochemistry, UNIL
Cluster Participants
Dr Sarah Fawcett, University of Cape Town, SA
Amelia Deary, University of Cape Town, SA
Dr Jerome Chappelaz, EPFL
Dr Christel Hassler, UNIL
Prof. Dr Fiamma Straneo, Scripps Institution of Oceanography, University of California, San Diego
Dr Ulrike Braeckman, Marine Biology Research Group, Ghent University