Marine‐terminating glaciers sustain high productivity in Greenland fjords

Abstract

Accelerated mass loss from the Greenland ice sheet leads to glacier retreat and an increasing input of glacial meltwater to the fjords and coastal waters around Greenland. These high latitude ecosystems are highly productive and sustain important fisheries, yet it remains uncertain how they will respond to future changes in the Arctic cryosphere. Here we show that marine-terminating glaciers play a crucial role in sustaining high productivity of the fjord ecosystems. Hydrographic and biogeochemical data from two fjord systems adjacent to the Greenland ice sheet, suggest that marine ecosystem productivity is very differently regulated in fjords influenced by either land-terminating or marine-terminating glaciers. Rising subsurface meltwater plumes originating from marine-terminating glaciers entrain large volumes of ambient deep water to the surface. The resulting upwelling of nutrient-rich deep water sustains a high phytoplankton productivity throughout summer in the fjord with marine-terminating glaciers. In contrast, the fjord with only land-terminating glaciers lack this upwelling mechanism, and is characterized by lower productivity.Data on commercial halibut landings support that coastal regions influenced by large marine-terminating glaciers have substantially higher marine productivity. These results suggest that a switch from marine-terminating to land-terminating glaciers can substantially alter the productivity in the coastal zone around Greenland with potentially large ecological and socio-economic implications.

Linking the Modern Distribution of Biogenic Proxies in High Arctic Greenland Shelf Sediments to Sea Ice, Primary Production, and Arctic‐Atlantic Inflow

“…The local influence of cold and turbid subglacial meltwaters originating from the Flade Isblink ice cap was also observed directly at the outlet of the glacier. It has been suggested that subglacial meltwater discharges from marine‐terminating glaciers could help promote primary productivity through increased nutrient supplies (e.g., Meire et al, ). According to the data from Dmitrenko et al (), the influence of the meltwater originating from this glacier only reaches a few kilometers away from the glacial tongue, only directly affecting Site k8 of this study.…”

Estimating Spring Terminus Submarine Melt Rates at a Greenlandic Tidewater Glacier Using Satellite Imagery

“…Given the potential importance of meltwater generation to fjord water properties and nutrient productivity (Meire et al, 2017), we here estimate the spring freshwater flux from submarine melting of the ice tongue. Using grounded terminus width (∼4,500 m), depth (∼250 m), and average velocity from March to May 2013 (∼6.9 km a −1 ), spring ice flux across the KNS grounding line was estimated to be 246 m 3 s −1 .…”

“…As such, the associated inputs of freshwater into the fjord at different depths from submarine melting may have a major impact on fjord water stratification, circulation and associated productivity (e.g., Motyka et al, 2013;Sciascia et al, 2013;Sutherland et al, 2014;Meire et al, 2017).…”

Upwelling of Macronutrients and Dissolved Inorganic Carbon by a Subglacial Freshwater Driven Plume in Bowdoin Fjord, Northwestern Greenland

“…Meire et al () have reported that phytoplankton productivity is regulated quite differently in fjords influenced by either marine‐terminating or land‐terminating glaciers. Phytoplankton are important primary producers, as they ensure a crucial energy supply to higher trophic animals within fjords.…”