Abstract. Freshwater discharge from glaciers is increasing across the Arctic in
response to anthropogenic climate change, which raises questions about the
potential downstream effects in the marine environment. Whilst a combination
of long-term monitoring programmes and intensive Arctic field campaigns have
improved our knowledge of glacier–ocean interactions in recent years,
especially with respect to fjord/ocean circulation, there are extensive
knowledge gaps concerning how glaciers affect marine biogeochemistry and
productivity. Following two cross-cutting disciplinary International Arctic
Science Committee (IASC) workshops addressing the importance of glaciers
for the marine ecosystem, here we review the state of the art concerning
how freshwater discharge affects the marine environment with a specific
focus on marine biogeochemistry and biological productivity. Using a series
of Arctic case studies (Nuup Kangerlua/Godthåbsfjord, Kongsfjorden,
Kangerluarsuup Sermia/Bowdoin Fjord, Young Sound and Sermilik Fjord), the
interconnected effects of freshwater discharge on fjord–shelf exchange,
nutrient availability, the carbonate system, the carbon cycle and the
microbial food web are investigated. Key findings are that whether the effect
of glacier discharge on marine primary production is positive or negative
is highly dependent on a combination of factors. These include glacier type
(marine- or land-terminating), fjord–glacier geometry and the limiting
resource(s) for phytoplankton growth in a specific spatio-temporal region
(light, macronutrients or micronutrients). Arctic glacier fjords therefore
often exhibit distinct discharge–productivity relationships, and multiple
case-studies must be considered in order to understand the net effects of
glacier discharge on Arctic marine ecosystems.
Simulations with the Marine Biogeochemistry Library (MARBL)
