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The waters on the West Greenland continental shelf and slope play an important role in the global climate system with their link to the subpolar North Atlantic Ocean circulation system and the Greenland Ice Sheet. Lately, low temperature waters on the West Greenland shelf have been observed as far south as ∼64°N and associated with a cold and relatively saline water mass originating north of Davis Strait in Baffin Bay referred to as Baffin Bay Polar Water (BBPW). Here we use long, seasonal hydrographic time series from West Greenland at ∼64°N to study how frequently BBPW is reaching this far south. The analysis covers the period 1950–2018 with a data gap between 1988 and 2005. BBPW was observed frequently and was responsible for the temperature changes observed in the late 1960s–1980s and more intermittently post-2008. Some of the large temperature changes we observe in the time series have previously been ascribed to “Great Salinity Anomalies” (GSAs) propagating around the subpolar North Atlantic Ocean circulation system. The prevailing view of the propagation of GSAs has been ascribed to advection of anomalies along the large-scale circulation system. Our study shows that BBPW may play an important role in the interpretation of GSAs and melt of the Greenland Ice Sheet. Large temporal temperature changes at ∼64°N are associated with arrival of BBPW from the north and not advection of anomalies with the large-scale current system from the south. This advocates for a shift in water masses caused by changes in the position and/or strength of oceanic currents.

Fjords form the gateway between the open ocean and the Greenland Ice Sheet (GIS) and consequently play a crucial role for the stability of the Ice Sheet. Hydrographic observations, especially with seasonal resolution, from these fjords are limited making it difficult to assess linkages between the fjord, coastal water masses, and freshwater discharge from GIS. Here we present a decade‐long monthly hydrographic time series from a southwest Greenland fjord in direct contact with GIS. Our observations reveal significant temporal and spatial water mass variations related to coastal, glacial, and atmospheric dynamics. During winter, the fjord circulation is dominated by seasonal dense coastal inflows and the timing of these inflows determines intermediate and deepwater temperatures. During summer, runoff from GIS leads to a pronounced freshening of the fjord. In general, the fjord's seasonal circulation system damps the seasonal variation in temperature in the fjord. This leads to a seasonal temperature range in the intermediate layer in the inner part of the fjord that is half the observed range at the fjord entrance. Changes in mean water temperatures in the intermediate layer seem predominantly linked to local coastal water masses, where cold winter/warm summer events decrease/increase the mean water temperatures. Consequently, these events play an important role in heat transport toward glacier termini.

The Greenland Ice Sheet releases large amounts of freshwater, which strongly influences the physical and chemical properties of the adjacent fjord systems and continental shelves. Glacial meltwater input is predicted to strongly increase in the future, but the impact of meltwater on the carbonate dynamics of these productive coastal systems remains largely unquantified. Here we present seasonal observations of the carbonate system over the year 2013 in the surface waters of a west Greenland fjord (Godthåbsfjord) influenced by tidewater outlet glaciers. Our data reveal that the surface layer of the entire fjord and adjacent continental shelf are undersaturated in CO2 throughout the year. The average annual CO2 uptake within the fjord is estimated to be 65 g C m-2 yr-1, indicating that the fjord system is a strong sink for CO2. The largest CO2 uptake occurs in the inner fjord near to the Greenland Ice Sheet and high glacial meltwater input during the summer months correlates strongly with low pCO2 values. This strong CO2 uptake can be explained by the thermodynamic effect on the surface water pCO2 resulting from the mixing of fresh glacial meltwater and ambient saline fjord water, which results in a CO2 uptake of 1.8 mg C kg-1 of glacial ice melted. We estimated that 28% of the CO2 uptake can be attributed to the input of glacial meltwater, while the remaining part is due to high primary production. Our findings imply that glacial melt\-water is an important driver for undersaturation in CO2 in fjord and coastal waters adjacent to large ice sheets.

Despite being a key zooplankton group, knowledge on krill biology from the Arctic is inadequate. The present study examine the functional biology and evaluate the trophic role of krill in the GodthAyenbsfjord (64 degrees N, 51 degrees W) SW Greenland, through a combination of fieldwork and laboratory experiments. Krill biomass was highest in the middle fjord and inner fjord, whereas no krill was found offshore. The dominating species Thysanoessa raschii revealed a type III functional response when fed with the diatom Thalassiosira weissflogii. At food saturation, T. raschii exhibited a daily ration of 1% body C d(-1). Furthermore, T. raschii was capable of exploiting plankton cells from 5 to 400 mu m, covering several trophic levels of the pelagic food web. The calculated grazing impact by T. raschii on the fjord plankton community was negligible. However, the schooling and migratory behaviour of krill will concentrate and elevate the grazing in specific areas of the euphotic zone

In order to assess the potential responses of Greenland’s coastal ecosystems to future climate change, we studied the hydrography and distribution of metazooplankton, along a transect from the slope waters beyond Fyllas Banke to the inner part of Godthåbsfjord, West Greenland, in July and August 2008, and estimated feeding rates for some of the larger species groups. Within the 4 regional domains that were covered in the study (continental slope, continental shelf, outer sill region, and main fjord basin), salty coastal water and glacial runoff mixed to various extents, and 7 water masses with specific characteristics were identified. The common large copepod species were Calanus finmarchicus, C. glacialis, C. hyperboreus, and Metridia longa. Small copepod genera included Microsetella, Pseudocalanus, and Oithona, while rotifers and gastropods (primarily pteropods) were also found in high abundance. Species could be linked to the specific water masses, e.g. Calanus spp. were primarily associated with oceanic or coastal waters, whereas M. longa, Microsetella sp., Pseudocalanus sp., and rotifers were mostly found inside the fjord. The combined biomass of the large zooplankton species (5.5 × 103 mg C m–2) was less than that of the small species (6.8 × 103 mg C m–2) averaged across all sampled stations along the transect. Estimated in situ grazing rates for the large copepod species were