A Simulation of Thermohaline Effects of a Great Salinity Anomaly

Häkkinen, Sirpa

doi:10.1175/1520-0442(1999)012<1781:asoteo>2.0.co;2

Cited by 131 publications

(84 citation statements)

References 27 publications

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“…Simulations of large events such as the GSA of the early 1970's show contrasting results. Häkkinen (1999) found in a regional model with no surface salinity restoring that GSAs strongly reduced the deep convection in the Labrador Sea and weakened the Atlantic MOC by up to 20%. Haak et al (2003) found in a higher resolution model with weak salinity restoring that convection in the Labrador Sea was only reduced for a few years and the Atlantic MOC was barely affected.…”

Section: Introductionmentioning

confidence: 75%

The role of salinity in the decadal variability of the North Atlantic meridional overturning circulation

2009

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An OGCM hindcast is used to investigate the linkages between North Atlantic Ocean salinity and circulation changes during . The focus is on the eastern subpolar region consisting of the Irminger Sea and the eastern North Atlantic where a careful assessment shows that the simulated interannual to decadal salinity changes in the upper 1500 m reproduce well those derived from the available record of hydrographic measurements. In the model, the variability of the Atlantic meridional overturning circulation (MOC) is primarily driven by changes in deep water formation taking place in the Irminger Sea and, to a lesser extent, the Labrador Sea. Both are strongly influenced by the North Atlantic Oscillation (NAO). The modeled interannual to decadal salinity changes in the subpolar basins are mostly controlled by circulation-driven anomalies of freshwater flux convergence, although surface salinity restoring to climatology and other boundary fluxes each account for approximately 25% of the variance. The NAO plays an important role: a positive NAO phase is associated with increased precipitation, reduced northward salt transport by the wind-driven intergyre gyre, and increased southward flows of freshwater across the Greenland-Scotland ridge. Since the NAO largely controlled deep convection in the subpolar gyre, fresher waters are found near the sinking region during convective events. This markedly differs from the active influence on the MOC that salinity exerts at decadal and longer timescales in most coupled models. The intensification of the MOC that follows a positive NAO phase by about 2 years does not lead to an increase in the northward salt transport into the subpolar domain at low frequencies because it is cancelled by the concomitant intensification of the subpolar gyre which shifts the subpolar front eastward and reduces the northward salt transport by the North Atlantic Current waters. This differs again from most coupled models, where the gyre intensification precedes that of the MOC by several years.3

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Section: Introductionmentioning

confidence: 75%

The role of salinity in the decadal variability of the North Atlantic meridional overturning circulation

2009

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“…Snow and ice cover have a large influence on both the local and remote climate (Magnusdottir et al 2004;Alexander et al 2004;Koenigk et al 2009;Deser et al 2010;Overland and Wang 2010). The export of freshwater from the Arctic alters the deep water formation in the North Atlantic (Häkkinen 1999;Haak et al 2003;Koenigk et al 2006). Dickson et al (1988) and Belkin et al (1998) suggested that the so called ''Great Salinity Anomaly'' in the early 70s was caused by previous large Fram Strait sea ice exports.…”

Section: Introductionmentioning

confidence: 98%

Arctic climate change in 21st century CMIP5 simulations with EC-Earth

et al. 2012

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The Arctic climate change is analyzed in an ensemble of future projection simulations performed with the global coupled climate model EC-Earth2.3. EC-Earth simulates the twentieth century Arctic climate relatively well but the Arctic is about 2 K too cold and the sea ice thickness and extent are overestimated. In the twenty-first century, the results show a continuation and strengthening of the Arctic trends observed over the recent decades, which leads to a dramatically changed Arctic climate, especially in the high emission scenario RCP8.5. The annually averaged Arctic mean near-surface temperature increases by 12 K in RCP8.5, with largest warming in the Barents Sea region. The warming is most pronounced in winter and autumn and in the lower atmosphere. The Arctic winter temperature inversion is reduced in all scenarios and disappears in RCP8.5. The Arctic becomes ice free in September in all RCP8.5 simulations after a rapid reduction event without recovery around year 2060. Taking into account the overestimation of ice in the twentieth century, our model results indicate a likely ice-free Arctic in September around 2040. Sea ice reductions are most pronounced in the Barents Sea in all RCPs, which lead to the most dramatic changes in this region. Here, surface heat fluxes are strongly enhanced and the cloudiness is substantially decreased. The meridional heat flux into the Arctic is reduced in the atmosphere but increases in the ocean. This oceanic increase is dominated by an enhanced heat flux into the Barents Sea, which strongly contributes to the large sea ice reduction and surface-air warming in this region. Increased precipitation and river runoff lead to more freshwater input into the Arctic Ocean. However, most of the additional freshwater is stored in the Arctic Ocean while the total Arctic freshwater export only slightly increases.

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“…Rudels et al, 2005;Latarius and Quadfasel, 2010), the Denmark Strait and the North Atlantic (Sutherland et al, 2009;Cox et al, 2010). Once in the North Atlantic, this freshwater and ice melt have the potential to influence deep convection and the thermohaline overturning (Manabe and Stouffer, 1999;Rennermalm et al, 2007;Talley, 2008) as well as the horizontal circulation in the subpolar gyre (Häkkinen, 1999).…”

Section: Introductionmentioning

confidence: 99%

Liquid export of Arctic freshwater components through the Fram Strait 1998–2011

et al. 2013

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Abstract. We estimated the magnitude and composition of southward liquid freshwater transports in the East Greenland Current near 79 • N in the Western Fram Strait between 1998 and 2011. Previous studies have found this region to be an important pathway for liquid freshwater export from the Arctic Ocean to the Nordic Seas and the North Atlantic subpolar gyre.Our transport estimates are based on six hydrographic surveys between June and September and concurrent data from moored current meters. We combined concentrations of liquid freshwater, meteoric water (river water and precipitation), sea ice melt and brine from sea ice formation, and Pacific Water, presented in Dodd et al. (2012), with volume transport estimates from an inverse model. The average of the monthly snapshots of southward liquid freshwater transports between 10.6 • W and 4 • E is 100 ± 23 mSv (3160 ± 730 km 3 yr −1 ), relative to a salinity of 34.9. This liquid freshwater transport consists of about 130 % water from rivers and precipitation (meteoric water), 30 % freshwater from the Pacific, and −60 % (freshwater deficit) due to a mixture of sea ice melt and brine from sea ice formation.Pacific Water transports showed the highest variation in time, effectively vanishing in some of the surveys. Comparison of our results to the literature indicates that this was due to atmospherically driven variability in the advection of Pacific Water along different pathways through the Arctic Ocean. Variations in most liquid freshwater component transports appear to have been most strongly influenced by changes in the advection of these water masses to the Fram Strait. However, the local dynamics represented by the volume transports influenced the liquid freshwater component transports in individual years, in particular those of sea ice melt and brine from sea ice formation.Our results show a similar ratio of the transports of meteoric water and net sea ice melt as previous studies.

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A Simulation of Thermohaline Effects of a Great Salinity Anomaly

Cited by 131 publications

References 27 publications

The role of salinity in the decadal variability of the North Atlantic meridional overturning circulation

The role of salinity in the decadal variability of the North Atlantic meridional overturning circulation

Arctic climate change in 21st century CMIP5 simulations with EC-Earth

Liquid export of Arctic freshwater components through the Fram Strait 1998–2011

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