Energetics of the Southern Ocean Mode

Jüling, André; Viebahn, Jan; Drijfhout, Sybren; Dijkstra, Henk A.

doi:10.1029/2018jc014191

Cited by 16 publications

(34 citation statements)

References 42 publications

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“…In this paper, we analysed the last 100 years of model output from a multi-century (250 years) control simulation of a highresolution version of CESM under a repeated seasonal forcing of the year 2000. We find four multiyear MRP events and, 20 in each event, (deep) convection causes vertical mixing of anomalous subsurface heat towards the surface where it melts the sea-ice and leads to the formation of the MRP. These processes of the formation and lifecycle of the MRP are broadly in agreement with the classical view as in Martinson et al (1981) and those described from other model results in Martin et al (2013), Dufour et al (2017) and Reintges et al (2017).…”

Section: Summary and Discussionmentioning

confidence: 88%

“…In the CESM, we find that the preconditioning of the subsurface density can be linked to an intrinsic dynamical ocean mode 25 in the Southern Ocean, the SOM, which is dominantly caused by eddy-mean flow interaction (Jüling et al, 2018). A positive phase of the SOM leads to positive subsurface OHC anomalies in the South Atlantic Ocean Le Bars et al (2016).…”

Section: Summary and Discussionmentioning

confidence: 90%

“…However, recently rather regular multidecadal patterns of internal variability have been found in strongly eddying ocean models Le Bars et al (2016). Analysis of the mechanism of this variability, the so-called Southern Ocean Mode (SOM), indicated that dynamical processes, involving eddy mean-flow interaction and eddy-topography interaction (Hogg and Blundell, 2006), are mainly responsible (Jüling et al, 2018). Recently, van Westen and Dijkstra (2017) have shown that the SOM variability also occurs in a high-resolution ocean-eddying version of the CESM.…”

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confidence: 99%

“…Recently, van Westen and Dijkstra (2017) have shown that the SOM variability also occurs in a high-resolution ocean-eddying version of the CESM. 20 In this paper, we pursue the idea of the possible existence of a preferred multidecadal time scale of MRP events in the Southern Ocean through preconditioning and subsequent convection, by analysing the results of an extended CESM simulation as in van Westen and Dijkstra (2017). In this multi-century CESM simulation, several MRP events are found and we analyse the processes involved in these events.…”

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confidence: 99%

“…Backtracking the particles (using the time-varying 3D velocity fields) shows that the particles mainly propagate along the Weddell Gyre and eventually enter the Polynya region(Figure 6b). The particles are initially released at 200 m and 500 m depths in the Polynya region on20 December model year 250. One obtains different trajectories when the particles are released in, for example, December model year 249.…”

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confidence: 99%

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Multidecadal Preconditioning of the Maud Rise Polynya Region

Westen¹,

Dijkstra²

2020

Preprint

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Abstract. In this paper, we consider Maud Rise polynya formation in a long (250 years) high-resolution (ocean 0.1°, atmosphere 0.5° horizontal model resolution) of the Community Earth System Model. We find a dominant multidecadal time scale in the occurrence of these Maud Rise polynyas. Analysis of the results leads us to the interpretation that a preferred time scale can be induced by the variability of the Weddell Gyre, previously identified as the Southern Ocean Mode. The large-scale pattern of heat content variability associated with the Southern Ocean Mode modifies the stratification in the Maud Rise region and leads to a preferred time scale in convection through preconditioning of the subsurface density, and consequently to polynya formation.

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Section: Summary and Discussionmentioning

confidence: 88%

Section: Summary and Discussionmentioning

confidence: 90%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Multidecadal Preconditioning of the Maud Rise Polynya Region

Westen¹,

Dijkstra²

2020

Preprint

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Eddy-mean flow interactions and vertical eddy energy redistribution associated with the standing meander in the Antarctic Circumpolar Current

Matsuta

Masumoto

2021

Preprint

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Recent studies suggest that local eddy-mean flow interactions associated with standing meanders play key roles in the dynamics of the Antarctic Circumpolar Current. Here we explore the importance of the local dynamics quantitatively with a viewpoint of energy transfer using the Lorentz diagram concept. Results confirm the importance of the eddy-mean flow interactions in the standing meander, showing that 55% of the wind energy input is converted to the eddy energy through the baroclinic instability in the standing meander region. It is also found that most of the eddy kinetic energy is dissipated local in the deeper layer due to the vertical energy redistribution governed by the vertical pressure flux. Contrary, the eddy effects are negligible outside the standing meander region.

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Circulation adjustment in the Arctic and Atlantic in response to Greenland and Antarctic mass loss

2021

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Following a high-end projection for mass loss from the Greenland and Antarctic ice-sheets, a freshwater forcing was applied to the ocean surface in the coupled climate model EC-Earthv2.2 to study the response to meltwater release assuming an RCP8.5 emission scenario. The meltwater forcing results in an overall freshening of the Atlantic that is dominated by advective changes, strongly enhancing the freshening due to dilution by Greenland meltwater release. The strongest circulation change occurs in the western North Atlantic subpolar gyre and in the gyre in the Nordic Seas, leaving the North Atlantic subpolar gyre the region where most advective salt export occurs. Associated with counteracting changes in both gyre systems, the response of the Atlantic Meridional Overturning Circulation is rather weak over the 190 years of the experiment; it reduces with only 1 Sv ($$= 10^6$$ = 10 6 m $$^3$$ 3 s $$^{-1}$$ - 1 ), compared to changes in the subpolar gyre of 5 Sv. This relative insensitivity of the AMOC to the forcing is attributed to enhanced convection in the Nordic Seas and stronger overflows that compensate reduced convection in the Labrador and Irminger Seas, and lead to higher sea surface temperatures (SSTs) in the former and lower SSTs in the latter region. The weakened subpolar gyre in the west also shifts the North Atlantic Current and the subpolar-subtropical gyre boundary; with the subtropical gyre expanding, and the western subpolar gyre contracting. The SST changes are associated with obduction of Atlantic waters in the Nordic Seas that would otherwise obduct in the western subpolar gyre. The anomalous SSTs also induce a coupled ocean-atmosphere feedback that further strengthens the Nordic Seas circulation and weakens the western subpolar gyre. This occurs because the anomalous SST-gradient enhances the westerlies, especially between 65$$^{\circ }$$ ∘ N and 70$$^{\circ }$$ ∘ N; the associated increase in windstress curl consequently enhances the gyre in the Nordic Seas. This feedback is driven by the Greenland mass loss; Antarctic meltwater discharge causes a weaker, opposite response and more particularly affects the South Atlantic salinity budget through northward advection of low-salinity waters from the Southern Ocean. This effect, however, becomes visible only hundred years after the onset of Antarctic mass loss. We conclude that the response to freshwater forcing from both ice caps can lead to a complex response in the Atlantic circulation systems with opposing effects in different subbasins. The relative strength of the response is time-dependent and largely governed by internal feedbacks; the forcing acts mainly as a trigger and is decoupled from the response.

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Energetics of the Southern Ocean Mode

Cited by 16 publications

References 42 publications

Multidecadal Preconditioning of the Maud Rise Polynya Region

Multidecadal Preconditioning of the Maud Rise Polynya Region

Eddy-mean flow interactions and vertical eddy energy redistribution associated with the standing meander in the Antarctic Circumpolar Current

Circulation adjustment in the Arctic and Atlantic in response to Greenland and Antarctic mass loss

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