The interaction between sea ice and salinity-dominated ocean circulation: implications for halocline stability and rapid changes of sea ice cover

Jensen, Mari F.; Nilsson, Johan; Nisancioglu, Kerim H.

doi:10.1007/s00382-016-3027-5

Cited by 22 publications

(18 citation statements)

References 59 publications

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“…For the stadial-interstadial transitions, these model results and the lack of synchronous changes in the data presented here suggest a large influence of atmospheric dynamics on the change in snow accumulation as well. This is further supported by other proxy evidence from central Greenland (Kapsner et al, 1995) and is similarly observed in West Antarctica . An increase of the advection of air masses from lower latitudes would result in an increase of the snow accumulation as more moisture is transported to the ice sheet but in unchanged sea-salt concentrations in the precipitation and subsequently the ice core, as these air masses still carry the same amount of sea-salt aerosol.…”

Section: Discussionsupporting

confidence: 87%

Decadal-scale progression of the onset of Dansgaard–Oeschger warming events

et al. 2019

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Abstract. During the last glacial period, proxy records throughout the Northern Hemisphere document a succession of rapid millennial-scale warming events, called Dansgaard–Oeschger (DO) events. A range of different mechanisms has been proposed that can produce similar warming in model experiments; however, the progression and ultimate trigger of the events are still unknown. Because of their fast nature, the progression is challenging to reconstruct from paleoclimate data due to the limited temporal resolution achievable in many archives and cross-dating uncertainties between records. Here, we use new high-resolution multi-proxy records of sea-salt (derived from sea spray and sea ice over the North Atlantic) and terrestrial (derived from the central Asian deserts) aerosol concentrations over the period 10–60 ka from the North Greenland Ice Core Project (NGRIP) and North Greenland Eemian Ice Drilling (NEEM) ice cores in conjunction with local precipitation and temperature proxies from the NGRIP ice core to investigate the progression of environmental changes at the onset of the warming events at annual to multi-annual resolution. Our results show on average a small lead of the changes in both local precipitation and terrestrial dust aerosol concentrations over the change in sea-salt aerosol concentrations and local temperature of approximately one decade. This suggests that, connected to the reinvigoration of the Atlantic meridional overturning circulation and the warming in the North Atlantic, both synoptic and hemispheric atmospheric circulation changes at the onset of the DO warming, affecting both the moisture transport to Greenland and the Asian monsoon systems. Taken at face value, this suggests that a collapse of the sea-ice cover may not have been the initial trigger for the DO warming.

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Section: Discussionsupporting

confidence: 87%

Decadal-scale progression of the onset of Dansgaard–Oeschger warming events

et al. 2019

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“…The process and triggering factor is, however, different from that proposed by Dokken et al (2013). Paper III, Stigebrandt (1981), Linders & Björk (2013) and Jensen et al (2016) all show that insufficient freshwater input at the surface is driving the change. This indicates that the Atlantic Water inflow is not a trigger, but a response variable to the "atlantification" and rapid climate shift events in the past, as discussed by Polyakov et al (2017) and Dokken et al (2013).…”

Section: Are the Changes Reversible?mentioning

confidence: 93%

“…Building on this model, Jensen et al (2016) found that the stratification in the model breaks down even for small freshwater inputs, before the vertical density difference vanishes, showing that a tiny stratification is not a possible solution. These findings correspond well with the mixing feedback and rapid climate shift documented in this thesis, and support that rapid climate shift events have taken place in the past climate history (Dokken et al, 2013).…”

Section: Are the Changes Reversible?mentioning

confidence: 99%

“…Hence, stratification and thickness of the sea ice cover are positively interrelated, and negatively correlated with the dependence on sea ice import/external freshwater input. Another, analytical study showed that when the stratification becomes weak enough, it breaks down abruptly before vanishing entirely (Jensen et al, 2016),…”

Section: In a Stage Of Transitionmentioning

confidence: 99%

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Arctic layer salinity controls heat loss from deep Atlantic layer in seasonally ice‐covered areas of the Barents Sea

Lind

Ingvaldsen

Furevik

2016

Geophysical Research Letters

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In the seasonally ice‐covered northern Barents Sea an intermediate layer of cold and relatively fresh Arctic Water at ~25–110 m depth isolates the sea surface and ice cover from a layer of warm and saline Atlantic Water below, a situation that resembles the cold halocline layer in the Eurasian Basin. The upward heat flux from the Atlantic layer is of major concern. What causes variations in the heat flux and how is the Arctic layer maintained? Using observations, we found that interannual variability in Arctic layer salinity determines the heat flux from the Atlantic layer through its control of stratification and vertical mixing. A relatively fresh Arctic layer effectively suppresses the upward heat flux, while a more saline Arctic layer enhances the heat flux. The corresponding upward salt flux causes a positive feedback. The Arctic layer salinity and the water column structures have been remarkably stable during 1970–2011.

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“…An increasing number of climate reconstructions from marine sediment cores support the existence of a temporal sea ice cover in the Nordic seas during the last glacial period (Dokken et al 2013;Hoff et al 2016). In particular, Dokken and Jansen (1999), Rasmussen and Thomsen (2004), Dokken et al (2013), and Ezat et al (2014) show that the hydrography of the eastern Nordic seas during stadial conditions resembles the Arctic Ocean today, with a warm subsurface below a cold and fresh surface layer, which is a stratification that may allow for the presence of a sea ice cover (Jensen et al 2016). During warm interstadials, the Nordic seas are shown to be less stratified, with warm Atlantic water close to the surface.…”

Section: Introductionmentioning

confidence: 99%

Large Changes in Sea Ice Triggered by Small Changes in Atlantic Water Temperature

2018

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The sensitivity of sea ice to the temperature of inflowing Atlantic water across the Greenland-Scotland Ridge is investigated using an eddy-resolving configuration of the Massachusetts Institute of Technology General Circulation Model with idealized topography. During the last glacial period, when climate on Greenland is known to have been extremely unstable, sea ice is thought to have covered the Nordic seas. The dramatic excursions in climate during this period, seen as large abrupt warming events on Greenland and known as Dansgaard-Oeschger (DO) events, are proposed to have been caused by a rapid retreat of Nordic seas sea ice. Here, we show that a full sea ice cover and Arctic-like stratification can exist in the Nordic seas given a sufficiently cold Atlantic inflow and corresponding low transport of heat across the Greenland-Scotland Ridge. Once sea ice is established, continued sea ice formation and melt efficiently freshens the surface ocean and makes the deeper layers more saline. This creates a strong salinity stratification in the Nordic seas, similar to today's Arctic Ocean, with a cold fresh surface layer protecting the overlying sea ice from the warm Atlantic water below. There is a nonlinear response in Nordic seas sea ice to Atlantic water temperature with simulated large abrupt changes in sea ice given small changes in inflowing temperature. This suggests that the DO events were more likely to have occurred during periods of reduced warm Atlantic water inflow to the Nordic seas.

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The interaction between sea ice and salinity-dominated ocean circulation: implications for halocline stability and rapid changes of sea ice cover

Cited by 22 publications

References 59 publications

Decadal-scale progression of the onset of Dansgaard–Oeschger warming events

Decadal-scale progression of the onset of Dansgaard–Oeschger warming events

Arctic layer salinity controls heat loss from deep Atlantic layer in seasonally ice‐covered areas of the Barents Sea

Large Changes in Sea Ice Triggered by Small Changes in Atlantic Water Temperature

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