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The Greenland ice sheet is melting, and the rate of ice loss has increased 6-fold since the 1980s. At the same time, the Arctic sea ice extent is decreasing. Meltwater runoff and sea ice reduction both influence light and nutrient availability in the coastal ocean, with implications for the timing, distribution, and magnitude of phytoplankton production. However, the integrated effect of both glacial and sea ice melt is highly variable in time and space, making it challenging to quantify. In this study, we evaluate the relative importance of these processes for the primary productivity of Disko Bay, west Greenland, one of the most important areas for biodiversity and fisheries around Greenland. We use a high-resolution 3D coupled hydrodynamic–biogeochemical model for 2004–2018 validated against in situ observations and remote sensing products. The model-estimated net primary production (NPP) varied between 90–147 gC m−2 yr−1 during 2004–2018, a period with variable freshwater discharges and sea ice cover. NPP correlated negatively with sea ice cover and positively with freshwater discharge. Freshwater discharge had a strong local effect within ∼ 25 km of the source-sustaining productive hot spots during summer. When considering the annual NPP at bay scale, sea ice cover was the most important controlling factor. In scenarios with no sea ice in spring, the model predicted a ∼ 30 % increase in annual production compared to a situation with high sea ice cover. Our study indicates that decreasing ice cover and more freshwater discharge can work synergistically and will likely increase primary productivity of the coastal ocean around Greenland.

The Danish Meteorological Institute (DMI) is the authority in charge of the sea ice service that supports mariners off the Greenlandic coast. DMI has offered ice charts and in-person consultancy for many years. Over time, the portfolio of sea ice products has extended to include forecast and automated retrievals and translations of remotely sensed data to sea ice products. Recently, DMI has launched an improved, high-resolution sea ice operational forecast system (SIOFS). The newly-launched DMI-SIOFS is updated with an improved model configuration with a nominal horizontal resolution of 5 km that predicts the ocean and sea ice states. The system is based on the coupling of the 3D ocean model Hybrid Coordinate Ocean Model (HYCOM; e.g., Chassignet et al. (2007)) with the Community Ice CodE model (CICE; e.g., Hunke and Dukowicz (1997); Hunke (2001)). Apart from the horizontal resolution, the sea ice component is improved with parameterization of features such as landfast sea ice and melt-ponds, as well as enhanced sea-ice salinity and thermodynamics schemes. The freshwater discharge from Greenland has also been upgraded by using inputs from the Geological Survey of Denmark and Greenland (GEUS; https://eng.geus.dk/) that improves the coastal ocean currents and, consequently, the sea ice transport nearshore Greenland. As a final product, a 144 hourly forecast of sea ice conditions is produced twice a day and released on Polarportal (http://polarportal.dk/en/home/).With a focus on the waters surrounding Greenland, this study introduces the DMI-SIOFS and provides the first evaluation for it in terms of predicted sea ice edge location – an essential diagnostic for mariners. To do so, we make use of the Integrated Ice Edge Error (IIEE) metric introduced by Goessling et al. (2016). In addition, we provide insights on the model response to different forcing.

In theory, the same sea-ice models could be used for both research and operations, but in practice, differences in scientific and software requirements and computational and human resources complicate the matter. Although sea-ice modeling tools developed for climate studies and other research applications produce output of interest to operational forecast users, such as ice motion, convergence, and internal ice pressure, the relevant spatial and temporal scales may not be sufficiently resolved. For instance, sea-ice research codes are typically run with horizontal resolution of more than 3 km, while mariners need information on scales less than 300 m. Certain sea-ice processes and coupled feedbacks that are critical to simulating the Earth system may not be relevant on these scales; and therefore, the most important model upgrades for improving sea-ice predictions might be made in the atmosphere and ocean components of coupled models or in their coupling mechanisms, rather than in the sea-ice model itself. This paper discusses some of the challenges in applying sea-ice modeling tools developed for research purposes for operational forecasting on short time scales, and highlights promising new directions in sea-ice modeling.

We establish a methodology for assimilating satellite observations of ice surface temperature (IST) into a coupled ocean and sea-ice model. The method corrects the 2 meter air temperature based on the difference between the modelled and the observed IST. Thus the correction includes biases in the surface forcing and the ability of the model to convert incoming parameters at the surface to a net heat flux. A multi-sensor, daily, gap-free surface temperature analysis has been constructed over the Arctic region. This study revealed challenges estimating the ground truth based on buoys measuring IST, as the quality of the measurement varied from buoy to buoy. With these precautions we find a cold temperature bias in the remotely sensed data, and a warm bias in the modelled data relative to ice mounted buoy temperatures, prior to assimilation. As a consequence, this study weighted the modelled IST and the observed IST equally in the correction. The impact of IST was determined for experiments with and without the assimilation of IST and sea-ice concentration. We find that assimilation of remotely sensed data results in a cooling of IST, which improves the timing of the snow melt onset. The improved snow cover in spring is only based on observations from one buoy, thus additional good quality observations could strengthen the conclusions. The ice cover and the sea-ice thickness are increased, primarily in the experiment without sea-ice concentration assimilation.

Variations in sea ice freeze onset and regional sea surface temperatures (SSTs) in Baffin Bay and Greenland Sea are linked to autumn surface air temperatures (SATs) around coastal Greenland through 500 hPa blocking patterns, 1979–2014. We find strong, statistically significant correlations between Baffin Bay freeze onset and SSTs and SATs across the western and southernmost coastal areas, while weaker and fewer significant correlations are found between eastern SATs, SSTs, and freeze periods observed in the neighboring Greenland Sea. Autumn Greenland Blocking Index values and the incidence of meridional circulation patterns have increased over the modern sea ice monitoring era. Increased anticyclonic blocking patterns promote poleward transport of warm air from lower latitudes and local warm air advection onshore from ocean–atmosphere sensible heat exchange through ice-free or thin ice-covered seas bordering the coastal stations. Temperature composites by years of extreme late freeze conditions, occurring since 2006 in Baffin Bay, reveal positive monthly SAT departures that often exceed 1 standard deviation from the 1981–2010 climate normal over coastal areas that exhibit a similar spatial pattern as the peak correlations.

The Arctic marine environment is undergoing a transition from thick multi-year to first-year sea-ice cover with coincident lengthening of the melt season. Such changes are evident in the Baffin Bay-Davis Strait-Labrador Sea (BDL) region where melt onset has occurred ~8 days decade−1 earlier from 1979 to 2015. A series of anomalously early events has occurred since the mid-1990s, overlapping a period of increased upper-air ridging across Greenland and the northwestern North Atlantic. We investigate an extreme early melt event observed in spring 2013. (~6σ below the 1981–2010 melt climatology), with respect to preceding sub-seasonal mid-tropospheric circulation conditions as described by a daily Greenland Blocking Index (GBI). The 40-days prior to the 2013 BDL melt onset are characterized by a persistent, strong 500 hPa anticyclone over the region (GBI >+1 on >75% of days). This circulation pattern advected warm air from northeastern Canada and the northwestern Atlantic poleward onto the thin, first-year sea ice and caused melt ~50 days earlier than normal. The episodic increase in the ridging atmospheric pattern near western Greenland as in 2013, exemplified by large positive GBI values, is an important recent process impacting the atmospheric circulation over a North Atlantic cryosphere undergoing accelerated regional climate change.

A number of recent studies have shown enhanced retreat of tidewater glaciers over much of southern and western Greenland. One of the fastest retreats has occurred at Jakobshavn Isbrae, with the rapid retreat linked to the arrival of relatively warm and saline Irminger water along the west coast of Greenland. Similar links to changes in ocean water masses on the coastal shelf of Greenland were also seen on the east coast. This study presents hydrographic data from Disko Bay, additionally revealing that there was also a significant warming of the cold polar water entering Disko Bay from the mid-to-late 1990s onward. This layer, which lies at a depth of ~30–200 m, warmed by 1°–2°C. The heat content of the polar water layer increased by a factor of 3.6 for the post-1997 period compared to the period prior to 1990. The heat content in the west Greenland Irminger water layer between the same periods increased only by a factor of 2, but contained more total heat. The authors suggest that the changes in the polar water layer are related to circulation changes in Baffin Bay.

The NASA announcement of record surface melting of the Greenland ice sheet in July 2012 led us to examine the atmospheric and oceanic climatic anomalies that are likely to have contributed to these exceptional conditions and also to ask the question of how unusual these anomalies were compared to available records. Our analysis allows us to assess the relative contributions of these two key influences to both the extreme melt event and ongoing climate change. In 2012, as in recent warm summers since 2007, a blocking high pressure feature, associated with negative NAO conditions, was present in the mid-troposphere over Greenland for much of the summer. This circulation pattern advected relatively warm southerly winds over the western flank of the ice sheet, forming a heat dome' over Greenland that led to the widespread surface melting. Both sea-surface temperature and sea-ice cover anomalies seem to have played a minimal role in this record melt, relative to atmospheric circulation. Two representative coastal climatological station averages and several individual stations in south, west and north-west Greenland set new surface air temperature records for May, June, July and the whole (JJA) summer. The unusually warm summer 2012 conditions extended to the top of the ice sheet at Summit, where our reanalysed (1994-2012) DMI Summit weather station summer (JJA) temperature series set new record high mean and extreme temperatures in 2012; 3-hourly instantaneous 2-m temperatures reached an exceptional value of 2.2 degrees C at Summit on 11 July 2012. These conditions translated into the record observed ice-sheet wide melt during summer 2012. However, 2012 seems not to be climatically representative of future average' summers projected this century.

The Atlantic Meridional Overturning Circulation (AMOC) is an important component of ocean thermohaline circulation. Melting of Greenland's ice sheet is freshening the North Atlantic; however, whether the augmented freshwater flux is disrupting the AMOC is unclear. Dense Labrador Sea Water (LSW), formed by winter cooling of saline North Atlantic water and subsequent convection, is a key component of the deep southward return flow of the AMOC. Although LSW formation recently decreased, it also reached historically high values in the mid-1990s, making the connection to the freshwater flux unclear. Here we derive a new estimate of the recent freshwater flux from Greenland using updated GRACE satellite data, present new flux estimates for heat and salt from the North Atlantic into the Labrador Sea and explain recent variations in LSW formation. We suggest that changes in LSW can be directly linked to recent freshening, and suggest a possible link to AMOC weakening., Labrador Sea convection and the Atlantic overturning circulation are sensitive to surface freshening of the North Atlantic. Here, the authors show that the recent increases in Arctic freshwater flux can directly weaken Labrador Sea convection and potentially affect the overturning circulation.

The effects of climate change on marine ecosystems and in particular on marine top predators are difficult to assess due to, among other things, spatial variability, and lack of clear delineation of marine habitats. The banks of West Greenland are located in a climate sensitive area and are likely to elicit pronounced responses to oceanographic changes in the North Atlantic. The recent increase in sea temperatures on the banks of West Greenland has had cascading effects on sea ice coverage, residency of top predators, and abundance of important prey species like Atlantic cod (Gadus morhua). Here, we report on the response of one of the top predators in West Greenland; the harbour porpoise (Phocoena phocoena). The porpoises depend on locating high densities of prey species with high nutritive value and they have apparently responded to the general warming on the banks of West Greenland by longer residence times, increased consumption of Atlantic cod resulting in improved body condition in the form of larger fat deposits in blubber, compared to the situation during a cold period in the 1990s. This is one of the few examples of a measurable effect of climate change on a marine mammal population.

During the early 2000s the Greenland Ice Sheet experienced the largest ice-mass loss of the instrumental record 1 , largely as a result of the acceleration, thinning and retreat of large outlet glaciers in West and southeast Greenland 2‐5 . The quasi-simultaneous change in the glaciers suggests a common climate forcing. Increasing air 6 and ocean 7,8 temperatures have been indicated as potential triggers. Here, we present a record of calving activity of Helheim Glacier, East Greenland, that extends back to about AD 1890, based on an analysis of sedimentary deposits from Sermilik Fjord, where Helheim Glacier terminates. Specifically, we use the annual deposition of sand grains as a proxy for iceberg discharge. Our record reveals large fluctuations in calving rates, but the present high rate was reproduced only in the 1930s. A comparison with climate indices indicates that high calving activity coincides with a relatively strong influence of Atlantic water and a lower influence of polar water on the shelf off Greenland, as well as with warm summers and the negative phase of the North Atlantic Oscillation. Our analysis provides evidence that Helheim Glacier responds to short-term fluctuations of large-scale oceanic and atmospheric conditions, on timescales of 3‐10 years. The forcings behind the rapid increase in mass loss from the Greenland Ice Sheet in the early 2000s (ref. 1) are still debated. It is unclear whether the mass loss will continue in the near future and,ifso,atwhatrate.Theseuncertaintiesareaconsequenceofour limited understanding of mechanisms regulating ice-sheet variability and the response of fast-flowing outlet glaciers to climate variability. In southeast Greenland, Helheim Glacier, one of the regions largestglaciers,thinned,acceleratedandretreatedduringtheperiod 20032005

Six historical sections across the West Greenland Current are examined. Three sections have been regularly occupied since the late 1950s, while the three southern ones have been taken since 1984. Significant variability is observed for the freshwater core of the coastal current on the shelf, with salinity varying by over 3 units between years. There is also significant variability in the shape and offshore position of the main shelf break front, leading to large variability in Eulerian velocities. Significant presence of Irminger Water is seen during the 1960s and the 2000s, being found right across the sections in recent years. Maximum mean transport relative to the 34.8 isohaline of 5.5 ± 3.9 Sv , relative to 700 db, for 1984–2005, is observed at the Cape Desolation section. Transports decrease to the north, with the majority of the exchange with the interior of the Labrador Sea occurring between Cape Desolation and Fylla Bank. Inter-decadal transport variability is observed at Fylla Bank while a decline in transports since peaks in the early 1990s is seen at Cape Farewell and Cape Desolation. Freshwater transport is largest at Cape Desolation, with a mean Summer transport of 60.2 ± 20.5 mSv . Freshwater transport increases slightly between Cape Farewell and Cape Desolation and we suggest it is related to local discharge by glaciers into Juliannehaab Bight, as well as the melting of sea-ice. We also find that years of high Greenland ice cap melt are consistently associated with years of high freshwater transport at Cape Desolation, suggesting a portion of the freshwater transport of the West Greenland Current may be associated with melt from the Greenland ice sheet. Finally, significantly enhanced freshwater transports (33 mSv at Cape Desolation compared to the long term mean) are seen in 2008, probably a signature of the record Arctic Ocean ice melt and export in 2007.

The response of the Greenland ice sheet to ongoing climate change remains an area of great uncertainty, with most previous studies having concentrated on the contribution of the atmosphere to the ice mass-balance signature. Here we systematically assess for the first time the influence of oceanographic changes on the ice sheet. The first part of this assessment involves a statistical analysis and interpretation of the relative changes and variations in sea-surface temperatures (SSTs) and air temperatures around Greenland for the period 1870-2007. This analysis is based on HadISST1 and Reynolds OI.v2 SST analyses, in situ SST and deeper ocean temperature series, surface-air-temperature records for key points located around the Greenland coast, and examination of atmospheric pressure and geopotential height from NCEP/NCAR reanalysis. Second, we carried out a novel sensitivity experiment in which SSTs were perturbed as input to a regional climate model, and document the resulting effects on simulated Greenland climate and surface mass balance. We conclude that sea-surface/ocean temperature forcing is not sufficient to strongly influence precipitation/snow accumulation and melt/runoff of the ice sheet. Additional evidence from meteorological reanalysis suggests that high Greenland melt anomalies of summer 2007 are likely to have been primarily forced by anomalous advection of warm air masses over the ice sheet and to have therefore had a more remote atmospheric origin. However, there is a striking correspondence between ocean warming and dramatic accelerations and retreats of key Greenland outlet glaciers in both southeast and southwest Greenland during the late 1990s and early 2000s. Copyright © 2008 John Wiley & Sons, Ltd.

Observations over past decades show a sudden switch of Jakobshavn Isbrae—a large outlet glacier feeding a deep-ocean fjord on Greenland’s west coast—from slow thickening to rapid thinning in 1997. This switch is associated with a doubling in glacier velocity. Hydrographic data show a concurrent sudden increase in subsurface ocean temperatures along the entire west coast of Greenland, suggesting that the changes in Jakobshavn Isbrae were triggered by the arrival of relatively warm water originating from the Irminger Sea. Observations over the past decades show a rapid acceleration of several outlet glaciers in Greenland and Antarctica1. One of the largest changes is a sudden switch of Jakobshavn Isbrae, a large outlet glacier feeding a deep-ocean fjord on Greenland’s west coast, from slow thickening to rapid thinning2 in 1997, associated with a doubling in glacier velocity3. Suggested explanations for the speed-up of Jakobshavn Isbrae include increased lubrication of the ice–bedrock interface as more meltwater has drained to the glacier bed during recent warmer summers4 and weakening and break-up of the floating ice tongue that buttressed the glacier5. Here we present hydrographic data that show a sudden increase in subsurface ocean temperature in 1997 along the entire west coast of Greenland, suggesting that the changes in Jakobshavn Isbrae were instead triggered by the arrival of relatively warm water originating from the Irminger Sea near Iceland. We trace these oceanic changes back to changes in the atmospheric circulation in the North Atlantic region. We conclude that the prediction of future rapid dynamic responses of other outlet glaciers to climate change will require an improved understanding of the effect of changes in regional ocean and atmosphere circulation on the delivery of warm subsurface waters to the periphery of the ice sheets.

The impact of the Greenland tip jet on the wintertime mixed layer of the southwest Irminger Sea is investigated using in situ moored profiler data and a variety of atmospheric datasets. The mixed layer was observed to reach 400 m in the spring of 2003 and 300 m in the spring of 2004. Both of these winters were mild and characterized by a low North Atlantic Oscillation (NAO) index. A typical tip jet event is associated with a low pressure system that is advected by upper-level steering currents into the region east of Cape Farewell and interacts with the high topography of southern Greenland. Heat flux time series for the mooring site were constructed that include the enhancing influence of the tip jet events. This was used to force a one-dimensional mixed layer model, which was able to reproduce the observed envelope of mixed layer deepening in both winters. The deeper mixed layer of the first winter was largely due to a higher number of robust tip jet events, which in turn was caused by the steering currents focusing more storms adjacent to southern Greenland. Application of the mixed layer model to the winter of 1994–95, a period characterized by a high-NAO index, resulted in convection exceeding 1700 m. This prediction is consistent with hydrographic data collected in summer 1995, supporting the notion that deep convection can occur in the Irminger Sea during strong winters.

Plankton samples and oceanographic data were obtained during transect studies across fishing banks over the Southwest Greenland shelf in June 1999, May, and July 2000. The study gives a detailed description of micro- and mesozooplankton distributions and community structures during spring bloom and post bloom periods. Plankton distributions were related to the physical environment described by a hydrodynamic ocean circulation model. More than 30 species and a larger number of taxonomic categories were identified in the zooplankton samples. Large copepodites of Calanus finmarchicus , Calanus glacialis , and Calanus hyperboreus generally dominated the micro- and mesozooplankton biomass, with Pseudocalanus spp., Metridia longa , and Oithona spp. comprising most of the remaining biomass. By number, bivalves larvae and relatively large copepod nauplii (>200 μm) dominated the zooplankton community (>50 μm) in May, whereas smaller copepod nauplii ( Thalassiosira spp. and Chaetoceros spp., generally dominated the biomass of the plankton community of the upper 100 m followed by heterotrophic flagellates, copepods, other invertebrates, and ciliates. Conversely in June (and July) during post bloom, large copepods were dominating. Hydrodynamic model simulations of ocean currents and trajectories of potential plankton transports showed differences in potential advection of plankton across shelf banks. The circulation around the banks seems to create retention areas entrapping plankton for periods. Model simulations predict that upwelling occurs west of the shelf banks and to a lesser extent in the deep channels separating the banks. This upwelling, caused by wind and tidal motions, probably increases productivity and carbon cycling over the shelf areas.

A review of the climate conditions off West Greenland during the past 50 years shows large variability in the atmospheric, oceanographic and sea-ice variables, as well as in fish stocks. A positive relationship is found between water temperature and the recruitment of cod and redfish, whereas the recruitment of shrimp and halibut is negatively related to temperature. Observed shifts in the hydrographic conditions during the second half of the 1990s indicate that some changes in the environment may be expected in the coming years. Relationships between the past variations in fish resources, hydrographic conditions, and the large-scale climatic conditions, as expressed by the North Atlantic Oscillation (NAO), strongly support the incorporation of environmental variability into prediction models for fish recruitment and therefore into the assessment of the fish resources.

The ocean circulation on the West Greenland shelf are modelled using a 3D finite element circulation model forced by wind data from the Danish Meteorological Institute-High-Resolution Limited Area Model operational atmospheric model for the Greenland area and tides at the open boundary. Residual anticyclonic eddies are generated around the shelf banks north of 64 ∘ N and areas of permanent upwelling are located west of the shelf banks. The potential distances of shrimp larvae transport from larval release to settling at the bottom were studied, using a particle-tracking model. Particles released (hatched shrimp larvae) south of 62 ∘ N had a probability of about 2% of being lost to the Canadian Shelf, whereas for particles released north of 64 ∘ N almost none were lost from the West Greenland Shelf. The particles tended to have long retention times at the shelf banks caused by the residual anticyclonic eddies. The retention times increased slightly for particles tracked at depths from 80 to 30 m with minor implications for potential transport distances of larval shrimp and plankton.

Open-ocean deep convection, one of the processes by which deep waters of the world's oceans are formed, is restricted to a small number of locations (for example, the Mediterranean and Labrador seas). Recently, the southwest Irminger Sea has been suggested as an additional location for open-ocean deep convection. The deep water formed in the Irminger Sea has the characteristic temperature and salinity of the water mass that fills the mid-depth North Atlantic Ocean, which had been believed to be formed entirely in the Labrador basin. Here we show that the most likely cause of the convection in the Irminger Sea is a low-level atmospheric jet known as the Greenland tip jet, which forms periodically in the lee of Cape Farewell, Greenland, and is associated with elevated heat flux and strong wind stress curl. Using a history of tip-jet events derived from meteorological land station data and a regional oceanic numerical model, we demonstrate that deep convection can occur in this region when the North Atlantic Oscillation Index is high, which is consistent with observations. This mechanism of convection in the Irminger Sea differs significantly from those known to operate in the Labrador and Mediterranean seas.

International audience; Sediment core ER07 from Sermilik Fjord by Helheim Glacier in Southeast Greenland was analysedfor alkenones to document sea surface temperature (SST) changes over the past 100 years. Thealkenone SST values, ranging from 8 to 12°C, contrasts with colder values (0-4°C) obtained fromrecent hydrographic surveys inside the fjord. We suggest that advection of allochtonous alkenonesproduced in the warm Irminger Current waters circulating on the shelf likely accounts for thisdifference. The temperature range of the alkenone-derived record is similar to in situ observationsof 8-11°C on the shelf just outside Sermilik Fjord, and its variability over the past 100 yearsresembles the constructed variability over the shelf using remote instrumental data. This suggeststhat oceanographic changes on the adjacent shelf are linked to regional changes of the IrmingerCurrent and the East Greenland Current. The subsurface water heat content has previously beensuggested as an important control on Greenland outlet glacier stability and underlined by an episodeof warm subsurface waters ~ 1940 concurrent with markedly increased calving and retreat ofHelheim Glacier. Our results therefore suggest that alkenone-derived SST time series from highsedimentation rate glacial fjords may provide a new approach for reconstruction of past changes ofshelf water properties and variability around Greenland.

Ice-rafted debris in fjord sediment cores provides information about outlet glacier activity beyond the instrumental time period. It tells us that the Helheim Glacier, Greenland’s third most productive glacier, responds rapidly to short-term (3 to 10 years) climate changes.

This chapter addresses aspects of open-ocean convection in the western North Atlantic, with particular emphasis on the area near southern Greenland and the impact of small-scale atmospheric patterns. Nearly a century ago it was hypothesized that deep convection occurred in the southwest Irminger Sea, and recently convection has been observed in the eastern Labrador Sea. It is argued that the interaction of wintertime low-pressure systems with the high topography of Greenland may lead to the deep mixed-layers in these two areas. Two small-scale atmospheric patterns, forward tip jets and reverse tip jets, result in intense winds on both sides of southern Greenland. The latter pattern is related to the barrier winds along southeast Greenland. In each case the winds blow over areas of closed oceanic circulation where the deep mixing appears to occur. The importance of the forward tip jet in the evolution of the mixed-layer of the southwest Irminger Sea has recently been established, and evidence suggests that during strong winters the overturning can be quite deep. Reverse tip jets may in turn have a similar impact on the eastern Labrador Sea, causing enhanced heat loss and convection. However, to demonstrate this conclusively, further work is necessary to sort out the interaction of the barrier winds and reverse tip jets with the oceanic circulation and pack-ice.

[1] We examine the historical variability of Irminger Water (IW) along 3 sections across the West Greenland Current over 1950–2005. Significant variability in the salinity, size and position of the IW core are seen over time. Some of the saltiest and warmest IW ever recorded have been seen since 1995 (comparable to previous maximums in the 1960s). During these periods, the volume of IW is also larger, leading to larger transports into the Labrador Sea. For the period 1984–2005 transports at Cape Farewell are 3.8 ± 0.9 Sv, 7.5 ± 2.2 × 1013 J and 8.5 ± 1.8 mSv of salt referenced to 35.0. LSW formation is also correlated to IW transport at Cape Farewell with a lag of one year (0.51).

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[1] The near-surface circulation of the Nordic Seas is basically cyclonic and consists of jets and recirculation cells, which are tightly linked to the bottom topography. Variable forcing by the large-scale rotation of the wind leads to a modulation in the strength of the gyres and their interconnecting jets. This is seen in drifter and altimeter data. Currents are stronger during winter and during phases of high North Atlantic Oscillation Index. The exchanges between the North Atlantic and the Nordic Seas do not seem to be directly affected by this variable forcing. The narrow boundary currents and the intergyre jets are subject to instability, causing mesoscale current fluctuations, which contribute to the stirring and mixing of Polar and Atlantic water masses.