96 research outputs found
Distinct Seasonal Primary Production Patterns in the Sub-Polar Gyre and Surrounding Seas
Primary production (PP) in the sub-polar region appears to be important for ocean carbon uptake but how the different water masses contribute to the PP occurring here has not yet been described. Using two models based on satellite observations of surface chlorophyll, light and temperature, seasonal patterns in the distribution of PP are shown here to differ in the sub-polar gyre south of the Greenland-Scotland Ridge (GSR) and surrounding water masses. Monthly averages of PP (2003â2013) were determined. Total and seasonal PP were similar in both models. Average PP in five of the domains (0.47â0.77 g C mâ2 dâ1) was well above the global average (0.37 g C mâ2 dâ1). Over the East Greenland shelf, however, total annual PP was estimated to be only 0.19 g C mâ2 dâ1. The Norwegian shelf was the most productive of the regions studied. âSpring bloomsâ appear sporadically as spikes in the annual distribution of PP in some regions/years, but do not emerge as a dominant feature in the average annual development of PP in any of the domains. For all regions, âź25% of the annual PP takes place in the period January-May. PP peaked over most of the study area at or around maximum insolation or temperature. PP in the study region as a whole appears to be more related to latitude or water masses than to bathymetry. In waters over the East Greenland shelf, the Norwegian shelf, and north of the GSR up to 50% of annual PP had taken place when âź50% of the annual flux of light has reached the surface. In contrast, only about 35% of annual PP had taken place in the sub-polar gyre and waters over the southern open shelf by this time. Light-use efficiency differences may be explained by differences in mixed layer depth (MLD). Multi-model Earth System model studies have indicated that climate change may decrease the MLD in the sub-polar gyre and suggest this may lead to a decrease in the PP occurring here. The results presented here, however, suggest that a shallower MLD could lead to an increase in PP.publishedVersio
Distinct Seasonal Primary Production Patterns in the Sub-Polar Gyre and Surrounding Seas
Primary production (PP) in the sub-polar region appears to be important for ocean carbon uptake but how the different water masses contribute to the PP occurring here has not yet been described. Using two models based on satellite observations of surface chlorophyll, light and temperature, seasonal patterns in the distribution of PP are shown here to differ in the sub-polar gyre south of the Greenland-Scotland Ridge (GSR) and surrounding water masses. Monthly averages of PP (2003â2013) were determined. Total and seasonal PP were similar in both models. Average PP in five of the domains (0.47â0.77 g C mâ2 dâ1) was well above the global average (0.37 g C mâ2 dâ1). Over the East Greenland shelf, however, total annual PP was estimated to be only 0.19 g C mâ2 dâ1. The Norwegian shelf was the most productive of the regions studied. âSpring bloomsâ appear sporadically as spikes in the annual distribution of PP in some regions/years, but do not emerge as a dominant feature in the average annual development of PP in any of the domains. For all regions, âź25% of the annual PP takes place in the period January-May. PP peaked over most of the study area at or around maximum insolation or temperature. PP in the study region as a whole appears to be more related to latitude or water masses than to bathymetry. In waters over the East Greenland shelf, the Norwegian shelf, and north of the GSR up to 50% of annual PP had taken place when âź50% of the annual flux of light has reached the surface. In contrast, only about 35% of annual PP had taken place in the sub-polar gyre and waters over the southern open shelf by this time. Light-use efficiency differences may be explained by differences in mixed layer depth (MLD). Multi-model Earth System model studies have indicated that climate change may decrease the MLD in the sub-polar gyre and suggest this may lead to a decrease in the PP occurring here. The results presented here, however, suggest that a shallower MLD could lead to an increase in PP.publishedVersio
Multibeam bathymetry and CTD measurements in two fjord systems in southeastern Greenland
We present bathymetry and hydrological observations collected in the summer of 2014 from two fjord systems in southeastern Greenland with a multibeam sonar system. Our results provide a detailed bathymetric map of the fjord complex around the island of Skjoldungen in Skjoldungen Fjord and the outer part of Timmiarmiut Fjord and show far greater depths compared to the International Bathymetric Chart of the Arctic Ocean. The hydrography collected shows different properties in the fjords with the bottom water masses below 240âŻm in Timmiarmiut Fjord being 1â2âŻÂ°C warmer than in the two fjords around Skjoldungen, but data also illustrate the influence of sills on the exchange of deeper water masses within fjords. Moreover, evidence of subglacial discharge in Timmiarmiut Fjord, which is consistent with satellite observations of ice mĂŠlange set into motion, adds to our increasing understanding of the distribution of subglacial meltwater
Evidence of local and regional freshening of Northeast Greenland coastal waters
The supply of freshwater to fjord systems in Greenland is increasing as a result of climate change-induced acceleration in ice sheet melt. However, insight into the marine implications of the melt water is impaired by lack of observations demonstrating the fate of freshwater along the Greenland coast and providing evaluation basis for ocean models. Here we present 13 years of summer measurements along a 120âkm transect in Young Sound, Northeast Greenland and show that sub-surface coastal waters are decreasing in salinity with an average rate of 0.12âÂąâ0.05 per year. This is the first observational evidence of a significant freshening on decadal scale of the waters surrounding the ice sheet and comes from a region where ice sheet melt has been less significant. It implies that ice sheet dynamics in Northeast Greenland could be of key importance as freshwater is retained in southward flowing coastal currents thus reducing density of water masses influencing major deep water formation areas in the Subarctic Atlantic Ocean. Ultimately, the observed freshening could have implications for the Atlantic meridional overturning circulation
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