Observations of the ocean response to cold air outbreaks and polar lows over the Nordic Seas

Isachsen, Pål Erik; Drivdal, Magnus; Eastwood, Steinar; Gusdal, Yvonne; Noer, Gunnar; Sætra, Øyvind

doi:10.1002/grl.50705

Cited by 15 publications

(26 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…These anticyclones drift westward in the basin, where they are trapped by the closed geostrophic contours. This view is supported by model simulations and by remote sensing and drifter datasets (Köhl 2007;Isachsen et al 2012). To date, however, there have been no direct observations of the water mass transformation process, the vertical structure of the eddies, or of their contribution to the lateral heat-salt flux in the Lofoten basin.…”

Section: Introductionmentioning

confidence: 84%

“…MLDs for 2010 were generally deeper than 2011; however, both series exhibit significant variability over time scales of several weeks. This variability likely reflects both the variability in air-sea interaction (e.g., passing storms; as in Isachsen et al 2013) and mesoscale eddy activity (e.g., Köhl 2007).…”

Section: ) Mixed Layer Depthmentioning

confidence: 99%

“…In the North Atlantic, the classic view of deep convection resulting from water mass transformation occurring only in a few isolated regions (e.g., the Labrador and Greenland Seas) has shifted to include densification occurring along the pathways of warmwater inflow (e.g., Mauritzen 1996a,b;Isachsen et al 2007). Further, the role of eddies shed by the warm-water boundary currents has also emerged as a key factor in the water mass modification and subsequent restratification, as seen in observations in the Labrador Sea (Lilly et al 2003;Chanut et al 2008;de Jong et al 2013) as well as models (Spall 2005;Deshayes et al 2009;Gelderloos et al 2011;Straneo 2006a,b).…”

Section: Introductionmentioning

confidence: 99%

“…1) in the transformation of Atlantic Water (AW) is increasingly being recognized (Isachsen et al 2007;Rossby et al 2009a). Situated between two branches of the inflowing current, the Lofoten basin exhibits the deepest AW layer of the entire Nordic Seas.…”

Section: Introductionmentioning

confidence: 99%

“…Through these lateral fluxes, the narrow boundary current is transformed into a broad region over which surface buoyancy losses are maximized (Spall 2011). Studies of the Nordic Seas have made use of rich but sparsely sampled hydrography (e.g., Nilsen and Falck 2006;Rossby et al 2009a;Mork et al 2014), surface altimetry (Volkov et al 2013), drifters (Andersson et al 2011;Poulain et al 1996;Koszalka et al 2013;Rossby et al 2009b;Voet et al 2010), and numerical models (Köhl 2007;Spall 2010;Isachsen et al 2012). High temporal resolution measurements of the vertical structure of hydrography and currents are currently lacking.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Observations of Water Mass Transformation and Eddies in the Lofoten Basin of the Nordic Seas

Richards

Straneo

2015

Journal of Physical Oceanography

View full text Add to dashboard Cite

The Lofoten basin of the Nordic Seas is recognized as a crucial component of the meridional overturning circulation in the North Atlantic because of the large horizontal extent of Atlantic Water and winter surface buoyancy loss. In this study, hydrographic and current measurements collected from a mooring deployed in the Lofoten basin from July 2010 to September 2012 are used to describe water mass transformation and the mesoscale eddy field. Winter mixed layer depths (MLDs) are observed to reach approximately 400 m, with larger MLDs and denser properties resulting from the colder 2010 winter. A heat budget of the upper water column requires lateral input, which balances the net annual heat loss of ;80 W m 22. The lateral flux is a result of mesoscale eddies, which dominate the velocity variability. Eddy velocities are enhanced in the upper 1000 m, with a barotropic component that reaches the bottom. Detailed examination of two eddies, from April and August 2012, highlights the variability of the eddy field and eddy properties. Temperature and salinity properties of the April eddy suggest that it originated from the slope current but was ventilated by surface fluxes. The properties within the eddy were similar to those of the mode water, indicating that convection within the eddies may make an important contribution to water mass transformation. A rough estimate of eddy flux per unit boundary current length suggests that fluxes in the Lofoten basin are larger than in the Labrador Sea because of the enhanced boundary current-interior density difference.

show abstract

Section: Introductionmentioning

confidence: 84%

Section: ) Mixed Layer Depthmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Observations of Water Mass Transformation and Eddies in the Lofoten Basin of the Nordic Seas

Richards

Straneo

2015

Journal of Physical Oceanography

View full text Add to dashboard Cite

show abstract

Wind‐Driven Cross‐Shelf Exchange—West Spitsbergen Current as a Source of Heat and Salt for the Adjacent Shelf in Arctic Winters

2018

View full text Add to dashboard Cite

Cross‐shelf exchange can drive substantial hydrographic changes on shelves and along slopes. In this study, time series from moorings, profiles collected by a tagged seal, atmospheric reanalysis data, and weather regimes classification were used to investigate cross‐shelf exchange at the slope‐shelf interface south‐west of Spitsbergen during the four winters 2011–2014. Assessment of Ekman transport (ET) as a driving force and linking cross‐shelf exchange to large‐scale weather patterns were in focus. Strong positive correlations were found between zonal ET and hydrographic observations on the shelf, indicating its strong impact on cross‐shelf exchange. Strong negative correlations were found between the meridional ET and temperature and salinity measured on the shelf in winter 2012, indicating a suppressing role of westerly winds on fresher and colder outflows from the Barents Sea. The ETs in a wider area near the Svalbard Archipelago show substantial variations on short‐term, interannual and long‐term time scales due to changes in large‐scale atmospheric patterns. The regional wind speed shows a significant negative trend in winters between 1992 and 2016. At the same time, cumulative winter zonal ET increased on the north‐western Spitsbergen shelf, indicating a higher overall cross‐shelf exchange along the western Spitsbergen shelf break, while meridional ET south‐west of Spitsbergen decreased, indicating a reduced outflow of fresher and colder water from the Barents Sea. For the time period between 1980 and 2016, the winter air and sea surface temperatures (sea‐ice fraction) exhibit significant positive (negative) trends which even multiplied by factor of 2–3 in winters 2004–2016.

show abstract

Higher ocean wind speeds during marine cold air outbreaks

Kolstad

2017

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

Marine cold air outbreaks (MCAOs) are large‐scale events in which cold air masses are advected over open ocean. It is well‐known that these events are linked to the formation of polar lows and other mesoscale phenomena associated with high wind speeds, and that they therefore in some cases represent a hazard to maritime activities. However, it is still unknown whether MCAOs are generally conducive to higher wind speeds than normal. Here this is investigated by comparing ocean near‐surface wind speeds during MCAOs in atmospheric reanalysis products with different horizontal grid spacings, along with two case‐studies using a convection‐permitting numerical weather prediction model. The study regions are the Labrador Sea and the Greenland–Iceland–Norwegian (GIN) Seas, where MCAOs have been shown to be important for air–sea interaction and deep water formation. One of the main findings is that wind speeds during the strongest MCAO events are higher than normal and higher than wind speeds during less severe events. Limited evidence from the case‐studies suggests that reanalyses with grid spacings of more than 50 km underestimate winds driven by the large ocean–atmosphere energy fluxes during MCAOs. The peak times of MCAOs usually occur when baroclinic waves pass over the regions. Therefore, the strong wind episodes during MCAOs generally last for just a few days. However, MCAOs as defined here can persist for 50 days or more.

show abstract

Observations of the ocean response to cold air outbreaks and polar lows over the Nordic Seas

Cited by 15 publications

References 11 publications

Observations of Water Mass Transformation and Eddies in the Lofoten Basin of the Nordic Seas

Observations of Water Mass Transformation and Eddies in the Lofoten Basin of the Nordic Seas

Wind‐Driven Cross‐Shelf Exchange—West Spitsbergen Current as a Source of Heat and Salt for the Adjacent Shelf in Arctic Winters

Higher ocean wind speeds during marine cold air outbreaks

Contact Info

Product

Resources

About