Arctic Mediterranean Exchanges: A consistent volume budget and trends in transports from two decades of observations

Abstract. The Arctic Mediterranean (AM) is the collective name for the Arctic Ocean, the Nordic Seas, and their adjacent shelf seas. Into this region, water enters through the Bering Strait (Pacific inflow) and through the passages across the Greenland-Scotland Ridge (Atlantic inflow) and then modified within the AM. The modified waters leave the AM in several flow branches, which are grouped into two different categories: (1) overflow of dense water through the deep passages across the Greenland-Scotland Ridge, and (2) outflow of light water – here termed surface outflow – on both sides of Greenland. These exchanges transport heat, salt, and other substances into and out of the AM and are important for conditions in the AM. They are also part of the global ocean circulation and climate system. Attempts to quantify the transports by various methods have been made for many years, but only recently, has the observational coverage become sufficiently complete to allow an integrated assessment of the AM-exchanges based solely on observations. In this study, we focus on the transport of water and have collected data on volume transport for as many AM-exchange branches as possible between 1993–2015. The total AM-import (oceanic inflows plus freshwater) is found to be 9.1 ± 0.7 Sv (1 Sv = 106 m3 s−1) and has a seasonal variation of amplitude close to 1 Sv and maximum import in October. Roughly one third of the imported water leaves the AM as surface outflow with the remaining two thirds leaving as overflow. The overflow is mainly produced from modified Atlantic inflow and around 70 % of the total Atlantic inflow is converted into overflow, indicating a strong coupling between these two exchanges. The surface outflow is fed from the Pacific inflow and freshwater, but is still ~ 2/3rds from modified Atlantic water. For the inflow branches and the two main overflow branches (Denmark Strait and Faroe Bank Channel), systematic monitoring of volume transport has been established since the mid-1990s and this allows us to estimate trends for the AM-exchanges as a whole. At the 95 % level, only the inflow of Pacific water through the Bering Strait showed a statistically significant trend, which was positive. Both the total AM-inflow and the combined transport of the two main overflow branches also showed trends consistent with strengthening, but they were not statistically significant. They do suggest, however, that any significant weakening of these flows during the last two decades is unlikely and the overall message is that the AM-exchanges remained remarkably stable in the period from the mid-1990s to the mid-2010s. The overflows are the densest source water for the deep limb of the North Atlantic part of the Meridional Overturning Circulation (AMOC), and this conclusion argues that the reported weakening of the AMOC was not due to overflow weakening or reduced overturning in the AM. Although the combined data set has made it possible to establish a consistent budget for the AM-exchanges, the observational coverage for some of the branches is limited, which introduces considerable uncertainty. This lack of coverage is especially extreme for the surface outflows through the Denmark Strait, the overflow across the Iceland-Faroe Ridge, and the inflow over the Scottish shelf. We recommend that more effort is put into observing these flows as well as maintaining the monitoring systems established for the other exchange branches.

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Arctic Mediterranean exchanges: a consistent volume budget and trends in transports from two decades of observations

Ocean Science ◽

10.5194/os-15-379-2019 ◽

2019 ◽

Vol 15 (2) ◽

pp. 379-399 ◽

Cited By ~ 22

Author(s):

Svein Østerhus ◽

Rebecca Woodgate ◽

Héðinn Valdimarsson ◽

Bill Turrell ◽

Laura de Steur ◽

...

Keyword(s):

Ocean Circulation ◽

Atlantic Water ◽

Volume Transport ◽

Meridional Overturning Circulation ◽

The Arctic ◽

Global Ocean ◽

Bering Strait ◽

Data Set ◽

Considerable Uncertainty ◽

Denmark Strait

Abstract. The Arctic Mediterranean (AM) is the collective name for the Arctic Ocean, the Nordic Seas, and their adjacent shelf seas. Water enters into this region through the Bering Strait (Pacific inflow) and through the passages across the Greenland–Scotland Ridge (Atlantic inflow) and is modified within the AM. The modified waters leave the AM in several flow branches which are grouped into two different categories: (1) overflow of dense water through the deep passages across the Greenland–Scotland Ridge, and (2) outflow of light water – here termed surface outflow – on both sides of Greenland. These exchanges transport heat and salt into and out of the AM and are important for conditions in the AM. They are also part of the global ocean circulation and climate system. Attempts to quantify the transports by various methods have been made for many years, but only recently the observational coverage has become sufficiently complete to allow an integrated assessment of the AM exchanges based solely on observations. In this study, we focus on the transport of water and have collected data on volume transport for as many AM-exchange branches as possible between 1993 and 2015. The total AM import (oceanic inflows plus freshwater) is found to be 9.1 Sv (sverdrup, 1 Sv =106 m3 s−1) with an estimated uncertainty of 0.7 Sv and has the amplitude of the seasonal variation close to 1 Sv and maximum import in October. Roughly one-third of the imported water leaves the AM as surface outflow with the remaining two-thirds leaving as overflow. The overflow water is mainly produced from modified Atlantic inflow and around 70 % of the total Atlantic inflow is converted into overflow, indicating a strong coupling between these two exchanges. The surface outflow is fed from the Pacific inflow and freshwater (runoff and precipitation), but is still approximately two-thirds of modified Atlantic water. For the inflow branches and the two main overflow branches (Denmark Strait and Faroe Bank Channel), systematic monitoring of volume transport has been established since the mid-1990s, and this enables us to estimate trends for the AM exchanges as a whole. At the 95 % confidence level, only the inflow of Pacific water through the Bering Strait showed a statistically significant trend, which was positive. Both the total AM inflow and the combined transport of the two main overflow branches also showed trends consistent with strengthening, but they were not statistically significant. They do suggest, however, that any significant weakening of these flows during the last two decades is unlikely and the overall message is that the AM exchanges remained remarkably stable in the period from the mid-1990s to the mid-2010s. The overflows are the densest source water for the deep limb of the North Atlantic part of the meridional overturning circulation (AMOC), and this conclusion argues that the reported weakening of the AMOC was not due to overflow weakening or reduced overturning in the AM. Although the combined data set has made it possible to establish a consistent budget for the AM exchanges, the observational coverage for some of the branches is limited, which introduces considerable uncertainty. This lack of coverage is especially extreme for the surface outflow through the Denmark Strait, the overflow across the Iceland–Faroe Ridge, and the inflow over the Scottish shelf. We recommend that more effort is put into observing these flows as well as maintaining the monitoring systems established for the other exchange branches.

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Arctic Mediterranean Exchanges: A consistent volume budget and trends in transports from two decades of observations

10.5194/egusphere-egu2020-11076 ◽

2020 ◽

Author(s):

Svein Østerhus ◽

Rebecca Woodgate ◽

Héðinn Valdimarsson ◽

Bill Turrell ◽

Laura de Steur ◽

...

Keyword(s):

Ocean Circulation ◽

Integrated Assessment ◽

Volume Transport ◽

The Arctic ◽

Global Ocean ◽

Lower Latitude ◽

Bering Strait ◽

Transport Time ◽

Shelf Seas ◽

Global Ocean Circulation

Conditions in the Arctic are in part driven by the ocean state in the Arctic Mediterranean (AM), the collective name for the Arctic Ocean, the Nordic Seas, and their adjacent shelf seas. Exchange between the lower latitude ocean basins and this region occurs through the Bering Strait (Pacific inflow) and through the passages across the Greenland-Scotland Ridge (Atlantic inflow). These waters are subsequently modified within the AM. The modified waters leave the AM in several flow branches, which are grouped into two different categories: (1) overflow of dense water through the deep passages across the Greenland-Scotland Ridge, and (2) outflow of light water (surface outflow) on both sides of Greenland. These exchanges transport heat and salt into and out of the AM and are important for conditions in the AM. They are also part of the global ocean circulation and climate system. Attempts to quantify the transports by various methods have been made for many years, but only recently, the observational coverage has become sufficiently complete to allow an integrated assessment of the AM-exchanges based solely on observations.In this EGU contribution, we focus on the observations (incl. volume transport time series) of all the main AM-exchange branches collected in the last 20 to 30 years.

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A stable Faroe Bank Channel overflow 1995–2015

10.5194/os-2016-56 ◽

2016 ◽

Author(s):

Bogi Hansen ◽

Karin Margretha Húsgarð Larsen ◽

Hjálmar Hátún ◽

Svein Østerhus

Keyword(s):

Acoustic Doppler Current Profiler ◽

Narrow Channel ◽

Volume Transport ◽

Meridional Overturning Circulation ◽

The Arctic ◽

Positive Trend ◽

The North ◽

Denmark Strait ◽

Current Profiler ◽

Meridional Overturning

Abstract. The Faroe Bank Channel is the deepest passage across the Greenland-Scotland Ridge (GSR), and through it, there is a continuous deep flow of cold and dense water passing from the Arctic Mediterranean into the North Atlantic and further to the rest of the World oceans. This FBC-overflow is part of the Atlantic Meridional Overturning Circulation (AMOC), which has recently been suggested to have weakened. From November 1995 to May 2015, the FBC-overflow has been monitored by a continuous ADCP (Acoustic Doppler Current Profiler) mooring, which has been deployed in the middle of this narrow channel. Combined with regular hydrography cruises and several short-term mooring experiments, this allows us to construct time series of volume transport and to follow changes in the hydrographic properties and density of the FBC-overflow. The mean kinematic overflow, derived from the velocity field solely, was found to be (2.2 ± 0.2) Sv (1 Sv = 106 m3 s−1) with a slight, but not statistically significant, positive trend. The coldest part, and probably the bulk, of the FBC-overflow warmed by a bit more than 0.1 °C, especially after 2002. This warming was, however, accompanied by increasing salinities, which seem to have compensated for the temperature-induced density decrease. Thus, the FBC-overflow has remained stable in volume transport as well as density during the two decades from 1995 to 2015. This is consistent with reported observations from the other main overflow branch, the Denmark Strait overflow, and the three Atlantic inflow branches to the Arctic Mediterranean that feed the overflows. If the AMOC has weakened during the last two decades, it is not likely to have been due to its northernmost extension – the exchanges across the Greenland-Scotland Ridge.

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The Norwegian node for the European Multidisciplinary Seafloor and water column Observatory

10.5194/egusphere-egu2020-7248 ◽

2020 ◽

Author(s):

Thibaut Barreyre ◽

Ilker Fer ◽

Bénédicte Ferré

Keyword(s):

Water Column ◽

Ocean Circulation ◽

Large Scale ◽

Water Mass ◽

Critical Role ◽

Meridional Overturning Circulation ◽

The Arctic ◽

Global Ocean ◽

Fram Strait ◽

Nordic Seas

NorEMSO is a coordinated, large-scale deep-ocean observation facility to establish the Norwegian node for the European Multidisciplinary Seafloor and water column Observatory (EMSO). The project aims to explore the under-sampled Nordic Seas to gain a better understanding of the critical role that they play in our climate system and global ocean circulation. An overarching scientific objective is to better understand the drivers for the temporal and spatial changes of water mass transformations, ocean circulation, acidification and thermo-chemical exchanges at the seafloor in the Nordic Seas, and to contribute to improvement of models and forecasting by producing and making available high quality, near real time data. NorEMSO will achieve this by combining expansion of existing and establishment of new observatory network infrastructure, as well as its coordination and integration into EMSO.NorEMSO comprises of three main components: moored observatories, gliders, and seafloor and water column observatory at the Mohn Ridge (EMSO-Mohn).Moored observation systems include an array of four moored observatories located at key positions in the Nordic Seas (Svin&#248;y, Station M, South Cape, and central Fram Strait).Gliders will be operated along five transects across both the Norwegian and the Greenland Seas to monitor circulation and water mass properties at those key locations. Transects in the Norwegian and Lofoten basins will focus on monitoring the Norwegian Atlantic Current, and a transect in Fram Strait will monitor properties and variability in the return Atlantic Water along the Polar Front in the northern Nordic Seas. In addition, transects in the Greenland and Iceland Seas will address the water mass transformation processes through wintertime open ocean convection, and the southbound transport of surface water from the Arctic Ocean and dense water that feeds the lower limb of the Atlantic Meridional Overturning Circulation in the East Greenland Current.EMSO-Mohn will establish, at the newly discovered hydrothermal site on the Mohn Ridge, a fixed-point seabed-water-column-coupled and wireless observatory with a multidisciplinary approach &#8211; from geophysics and physical oceanography to ecology and microbiology. It is primarily directed at understanding hydrothermal fluxes and associated hydrothermal plume dynamics in the water column and how it disperses in an oceanographic front over the Mohn Ridge.Following EMSO philosophy, NorEMSO will provide data and platforms to a large and diverse group of users, from scientists and industries to institutions and policy makers. The observations will serve climate research, ocean circulation understanding, numerical operational models, design of environmental policies, and education.

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Microbial responses to the release of DOC by sea ice and glacier melting in the East Greenland System

10.5194/egusphere-egu2020-10718 ◽

2020 ◽

Author(s):

Alba Filella Lopez de Lamadrid ◽

Anja Engel

Keyword(s):

Ocean Circulation ◽

Atlantic Water ◽

The Arctic ◽

Coastal System ◽

East Greenland ◽

East Greenland Current ◽

Enhanced Production ◽

Denmark Strait ◽

Variable Environments ◽

Microbial Responses

Freshwater discharge around Greenland has more than doubled during the last decade. Understanding the associated physical and biogeochemical impacts in the ocean is of great importance for future predictions of ocean circulation, productivity and feedbacks within the Earth system. In summer 2019 we performed several cross-shore sections passing through the highly variable environments and physical regimes along the east Greenland coastline. Microbial communities showed distinct latitudinal and meridional distributions. Water mass characteristics played a major role in controlling the abundances of organisms with few groups appearing in significant numbers in coastal (colder and fresher) waters. Surface polar waters rich in dissolved organic carbon (DOC) flow south in the East Greenland Current maintaining a high DOC signal in inshore waters. Further optical analyses on the DOC fraction will determine what fractions of this material originate from long scale transport out of the Arctic. Of particular interest was an enhanced production of gel particles rich in carbon in an area extending across Denmark Strait, from close to Scoresby Sund to north of Iceland. Significant concentrations (e.g. 80 &#181;g X.G. eq. L-1) of these transparent exopolymer particles (TEP) were even found deeper than 100m, which is highly unusual. Given the role of TEP as a binding agent for sinking particles, enhancing the sinking of carbon in the water column, it is of interest to know why such a TEP hotspot arises. We hypothesize that it could be either related to circulation through the Strait or the timing of bloom dynamics in this region prior to our cruise. &#160;Our main conclusion from preliminary data analysis is that the east Greenland coastal system is highly dynamic with mixed properties reflecting various degrees of mixing between southward flowing Polar Water and warmer Atlantic water masses.

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Characteristics and causes of Deep Western Boundary Current transport variability at 34.5° S during 2009–2014

10.5194/os-2016-76 ◽

2016 ◽

Author(s):

Christopher S. Meinen ◽

Silvia L. Garzoli ◽

Renellys C. Perez ◽

Edmo Campos ◽

Alberto R. Piola ◽

...

Keyword(s):

Volume Transport ◽

Horizontal Resolution ◽

Western Boundary Current ◽

Meridional Overturning Circulation ◽

Time Variability ◽

Western Boundary ◽

Boundary Current ◽

Meridional Heat Transport ◽

Data Set ◽

Deep Western Boundary Current

Abstract. The Deep Western Boundary Current (DWBC) at 34.5° S in the South Atlantic carries a significant fraction of the cold deep limb of the Meridional Overturning Circulation (MOC), and therefore its variability affects both the meridional heat transport and the regional and global climate. Nearly six years of observations from a line of pressure-equipped inverted echo sounders (PIES) have yielded an unprecedented data set for studying the characteristics of the time-varying DWBC volume transport at 34.5° S. Furthermore, the horizontal resolution of the observing array was greatly improved in December 2012 with the addition of two current-and-pressure-equipped inverted echo sounders (CPIES) at the midpoints of three of the existing sites. Regular hydrographic sections along the PIES/CPIES line confirm the presence of recently-ventilated North Atlantic Deep Water carried by the DWBC. The time-mean absolute geostrophic transport integrated within the DWBC layer, defined between 800–4800 dbar, and within longitude bounds of 51.5° W to 44.5° W is −15 Sv (1 Sv = 106 m3 s−1; negative indicates southward flow). The observed peak-to-peak range in volume transport using these integration limits is from −89 Sv to &plus;50 Sv, and the temporal standard deviation is 23 Sv. Testing different vertical integration limits based on time-mean water-mass property levels yields small changes to these values, but no significant alteration to the character of the transport time series. The time-mean southward DWBC flow at this latitude is confined west of 49.5° W, with recirculations dominating the flow further offshore. As with other latitudes where the DWBC has been observed for multiple years, the time variability greatly exceeds the time-mean, suggesting the presence of strong coherent vortices and/or Rossby Wave-like signals propagating to the boundary from the interior.

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Overflow of cold water across the Iceland-Faroe Ridge through the Western Valley

10.5194/os-2018-40 ◽

2018 ◽

Cited By ~ 2

Author(s):

Bogi Hansen ◽

Karin Margretha Húsgarð Larsen ◽

Steffen Malskær Olsen ◽

Detlef Quadfasel ◽

Kerstin Jochumsen ◽

...

Keyword(s):

Satellite Altimetry ◽

Cold Water ◽

Large Fraction ◽

Acoustic Doppler Current Profiler ◽

Atlantic Water ◽

Volume Transport ◽

Meridional Overturning Circulation ◽

Direct Measurements ◽

Current Profiler ◽

Meridional Overturning

Abstract. The Iceland-Faroe Ridge (IFR) is considered to be the third-most important passage for dense overflow water from the Nordic Seas feeding into the lower limb of the Atlantic Meridional Overturning Circulation with a volume transport on the order of 1 Sv (106 m3 s−1). The Western Valley, which is the northernmost deep passage across the IFR, has been presumed to supply a strong and persistent overflow (WV-overflow), contributing a large fraction of the total overflow across the IFR. However, prolonged measurements of this transport are so far missing. In order to quantify the flow by direct measurements, three instrumental packages were deployed close to the sill of the Western Valley for 278 days (2016–2017) including an Acoustic Doppler Current Profiler at the expected location of the overflow core. The average volume transport of WV-overflow during this field experiment was found to be less than 0.03 Sv. Aided by the observations and a two-layer hydraulic model, we argue that the reason for this low value is the inflow of warm Atlantic Water to the Norwegian Sea in the upper layers suppressing the deep overflow. The link between deep and surface flows explains an observed relationship between overflow and sea level slope as measured by satellite altimetry. This relationship, combined with historical hydrographic measurements allows us to conclude that the volume transport of WV-overflow most likely has been less than 0.1 Sv on average since the beginning of regular satellite altimetry in 1993. Our new direct measurements do not allow us to present an updated estimate of the total overflow across the IFR, but they indicate that it may well be considerably less than 1 Sv.

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A global high-resolution data set of ice sheet topography, cavity geometry and ocean bathymetry

10.5194/essd-2016-3 ◽

2016 ◽

Cited By ~ 4

Author(s):

Janin Schaffer ◽

Ralph Timmermann ◽

Jan Erik Arndt ◽

Steen Savstrup Kristensen ◽

Christoph Mayer ◽

...

Keyword(s):

High Resolution ◽

Continental Shelf ◽

Ice Sheet ◽

The Arctic ◽

Global Ocean ◽

Data Set ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

Surface Topographies ◽

The Antarctic

Abstract. The ocean plays an important role in modulating the mass balance of the polar ice sheets by interacting with the ice shelves in Antarctica and with the marine-terminating outlet glaciers in Greenland. Given that the flux of warm water onto the continental shelf and into the sub-ice cavities is steered by complex bathymetry, a detailed topography data set is an essential ingredient for models that address ice-ocean interaction. We followed the spirit of the global RTopo-1 data set and compiled consistent maps of global ocean bathymetry, upper and lower ice surface topographies and global surface height on a spherical grid with now 30-arc seconds resolution. We used the General Bathymetric Chart of the Oceans (GEBCO_2014) as the backbone and added the International Bathymetric Chart of the Arctic Ocean version 3 (IBCAOv3) and the International Bathymetric Chart of the Southern Ocean (IBCSO) version 1. While RTopo-1 primarily aimed at a good and consistent representation of the Antarctic ice sheet, ice shelves and sub-ice cavities, RTopo-2 now also contains ice topographies of the Greenland ice sheet and outlet glaciers. In particular, we aimed at a good representation of the fjord and shelf bathymetry surrounding the Greenland continent. We corrected data from earlier gridded products in the areas of Petermann Glacier, Hagen Bræ and Sermilik Fjord assuming that sub-ice and fjord bathymetries roughly follow plausible Last Glacial Maximum ice flow patterns. For the continental shelf off northeast Greenland and the floating ice tongue of Nioghalvfjerdsfjorden Glacier at about 79° N, we incorporated a high-resolution digital bathymetry model considering original multibeam survey data for the region. Radar data for surface topographies of the floating ice tongues of Nioghalvfjerdsfjorden Glacier and Zachariæ Isstrøm have been obtained from the data centers of Technical University of Denmark (DTU), Operation Icebridge (NASA/NSF) and Alfred Wegener Institute (AWI). For the Antarctic ice sheet/ice shelves, RTopo-2 largely relies on the Bedmap-2 product but applies corrections for the geometry of Getz, Abbot and Fimbul ice shelf cavities. The data set is available in full and in regional subsets in NetCDF format from the PANGAEA database at https://doi.pangaea.de/10.1594/PANGAEA.856844.

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Impact of Arctic gateways closure on the Atlantic Meridional Overturning Circulation in the Pliocene

10.5194/egusphere-egu21-9760 ◽

2021 ◽

Author(s):

Julia Weiffenbach ◽

Michiel Baatsen ◽

Anna von der Heydt

Keyword(s):

Boundary Conditions ◽

North Atlantic ◽

Atlantic Meridional Overturning Circulation ◽

Meridional Overturning Circulation ◽

Sea Surface ◽

The Arctic ◽

Bering Strait ◽

Overturning Circulation ◽

The North ◽

Meridional Overturning

The mid-Pliocene climate is the most recent geological period with a greenhouse gas concentration of approximately 400 ppmv, similar to the present day. Proxy reconstructions indicate enhanced warming in the high North Atlantic in the mid-Pliocene, which has been suggested to be a response to a stronger Atlantic Meridional Overturning Circulation (AMOC). PlioMIP2 ensemble results show a stronger AMOC and simulated North Atlantic sea surface temperatures (SSTs) match reconstructions better than PlioMIP1. A major difference between PlioMIP1 and PlioMIP2 is the closure of the Bering Strait and Canadian Archipelago in the Pliocene. Previous studies have shown that closure of these Arctic gateways leads to an enhanced AMOC due to altered freshwater fluxes in the Arctic.Analysis of our Community Earth System Model (CESM1) simulations shows that the simulated increase in North Atlantic SSTs and strengthened AMOC in the Pliocene is a result of Pliocene boundary conditions rather than CO2 concentration increase. Here we compare results from two runs with pre-industrial boundary conditions and 280 and 560 ppmv CO2 concentrations and three runs with PlioMIP2 boundary conditions and 280, 400 and 560 ppmv CO2 concentrations. Results show a 10-15% stronger AMOC in the Pliocene simulations as well as enhanced warming and saltening of the North Atlantic sea surface. While there is a stronger AMOC, the Atlantic northward ocean heat transport (OHT) in the Pliocene simulations only increases 0-3% with respect to the pre-industrial. Analysis indicates there is an altered relationship between the AMOC and OHT in the Pliocene, pointing to fundamentally different behavior of the AMOC in the Pliocene simulations. This is supported by a specific spatial pattern of deep water formation (DWF) areas in the Pliocene simulations that is significantly different from that of the pre-industrial. In the Pliocene simulations, DWF areas adjacent to south Greenland disappear and new DWF areas appear further southwards in the Labrador Sea off the coast of Newfounland. These results indicate that insight into the effect of the palaeogeographic boundary conditions is crucial to understanding the Pliocene climate and its potential as a geological equivalent to a future greenhouse climate.

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Evaluating Met Office uncoupled and coupled forecasts during the Iceland Greenland Seas Project field campaign in 2018

10.5194/egusphere-egu21-12533 ◽

2021 ◽

Author(s):

Chris Barrell ◽

Ian Renfrew ◽

Steven Abel ◽

Andrew Elvidge ◽

John King

Keyword(s):

Sea Ice ◽

Ocean Circulation ◽

Rapid Change ◽

Coupled Model ◽

Vital Role ◽

Meridional Overturning Circulation ◽

Global Ocean ◽

Near Surface ◽

Field Campaign ◽

Important Region

<div> During a cold-air outbreak (CAO) a cold polar airmass flows from the frozen land or ice surface, over the marginal ice zone (MIZ), then out over the comparatively warm open ocean. This constitutes a dramatic change in surface temperature, roughness and moisture availability, typically causing rapid change in the atmospheric boundary layer.&#160;Consequently, CAOs are associated with a range of severe mesoscale weather phenomena and accurate forecasting is crucial.&#160;Over the Nordic Seas CAOs also play a vital role in global ocean circulation, causing densification and sinking of ocean waters that form the headwaters of the Atlantic meridional overturning circulation.&#160; </div><div> To tackle the lack of observations during wintertime CAOs and improve scientific understanding in this important region, the Iceland Greenland Seas Project (IGP) undertook an extensive field campaign during February and March 2018. Aiming to&#160;characterise&#160;the atmospheric forcing and the ocean response, particularly in and around the MIZ, the IGP made coordinated ocean-atmosphere measurements, involving a research vessel, a research aircraft, a meteorological buoy, moorings, sea gliders and floats.&#160;&#160; </div><div> The work presented here employs these novel observational data to evaluate&#160;output&#160;from&#160;the&#160;UK&#160;Met Office global operational&#160;forecasting&#160;system&#160;and&#160;from a pre-operational&#160;coupled&#160;ocean-ice-atmosphere&#160;system.&#160;The Met Office aim to transition to a coupled operational forecast in the coming years,&#160;thus&#160;verification of model versions in development is&#160;essential. Results show&#160;that&#160;this&#160;coupled model&#8217;s&#160;sea ice is&#160;generally&#160;more accurate&#160;than&#160;a persistent field.&#160;However,&#160;it&#160;can also suffer from cold-biased sea surface temperatures around the MIZ,&#160;which influences&#160;the modelled near-surface meteorology.&#160;Both these effects demonstrate the crucial importance of accurate sea ice simulation in coupled&#160;model forecasting&#160;in the&#160;high latitudes. Hence,&#160;an ice edge metric is then used to quantify the accuracy of&#160;the coupled model MIZ edge at two ocean grid resolutions.&#160; </div>

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