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.
Highlights
Air temperatures in the Arctic have increased substantially in recent years leading to a reduction in sea ice and the melting of glaciers at unprecedented rates (Bamber, Van Den, Ettema, Lenaerts, & Rignot, 2012; Comiso, Parkinson, Gersten, & Stock, 2008)
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
We find that ecosystem productivity during summer is higher in the fjord with marine-terminating glaciers compared to the fjord which only has land-terminating glaciers
Summary
Air temperatures in the Arctic have increased substantially in recent years leading to a reduction in sea ice and the melting of glaciers at unprecedented rates (Bamber, Van Den, Ettema, Lenaerts, & Rignot, 2012; Comiso, Parkinson, Gersten, & Stock, 2008). While the ecological consequences of the decreasing sea ice have received attention (Wassmann & Reigstad, 2011), the impact of increased glacial melting on Arctic marine ecosystems remains largely unstudied. The Greenland ice sheet currently discharges ~1000 Gt yearÀ1 of freshwater into the coastal ocean, originating from both meltwater runoff and solid ice discharge (Bamber et al, 2012). Our understanding of how glaciers and glacial meltwater impact the biogeochemistry and productivity of the coastal region around Greenland is currently limited, which makes it difficult to predict how this region will be affected by future climate change. We present data from two different fjord systems adjacent to Greenland ice sheet that are influenced by either land-terminating or marine-terminating glaciers. The resulting impact on the productivity of the coastal zone around Greenland could have large socio-economic implications
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