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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.

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.