Mixed layer depth (MLD) variability in the southern Bay of Biscay. Deepening of winter MLDs concurrent with generalized upper water warming trends?

Cabrillo, Raquel Somavilla; González-Pola, César; Ruiz-Villarreal, Manuel; Montero, Alicia Lavín

doi:10.1007/s10236-011-0407-6

Cited by 31 publications

(27 citation statements)

References 47 publications

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“…when heat loss is concentrated in intense mixing events, rather than distributed evenly but more weakly throughout the winter (Marshall & Schott, 1999;Somavilla et al, 2011;Våge et al, 2008). Thus, changes in the maximum heat loss registered every winter and in the number of heat loss events higher than the particular threshold defining strong heat loss events are also investigated.…”

Section: Changes In Air-sea Heat Exchangessupporting

confidence: 52%

“…convection episodes appear more likely to occur when the heat loss is concentrated in intense mixing events (Marshall & Schott, 1999;Somavilla et al, 2011;Våge et al, 2008). This could have been the case before the 1980s, thereby explaining the deeper d nb than h. After the 1980s, this could raise the question of whether our approach may be overlooking some intense mixing events that could have penetrated the dome.…”

Section: 1029/2018jc014249mentioning

confidence: 99%

“…As the amount of heat that must be removed from the buoyant waters by air-sea fluxes increases, it becomes more difficult for deep convection to reach a particular depth (Frajka-Williams et al, 2016). Conversely, once the water column has been completely homogenized from the surface to the bottom, the stratification is not recovered immediately, and convective mixing can easily progress to great depths the following winter (Frajka-Williams et al, 2016;Somavilla et al, 2011). This would have facilitated more frequent occurrences of deep convection before the 1980s.…”

Section: 1029/2018jc014249mentioning

confidence: 99%

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Draining and Upwelling of Greenland Sea Deep Waters

Somavilla

2019

JGR Oceans

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Since the beginning of the 1980s, deep convection has ceased in the Greenland Sea. The effects of this halt on the intense warming and salinification of Greenland Sea deep waters and on the “dome collapse” (sinking of the dome) have been intensively studied. However, their causes and the potential outflow of Greenland Sea deep and bottom waters toward southern adjacent basins have remained less investigated and are the focus of this work. Combining oceanic and atmospheric in situ data, together with satellite and reanalysis data, it is found that there is not a unique factor responsible for the halt of deep convection in the Greenland Sea. Changes in the Ekman pumping seem to only explain one tenth of the observed deepening of isopycnals of 1,300 m in the central Greenland Sea (dome collapse). Since the early 1980s, in addition, a decrease in the mean net heat loss from the ocean to the atmosphere and in the intensity and number of intense heat loss events would have contributed to the decrease in both the intensity of convective mixing and the generation of dense deep waters. The generation of waters not sufficiently dense to contribute to the reservoir of water below the Greenland Sea dome would have led to its emptying and sinking. More importantly, it is found that in situ evidence of a sustained bottom‐water upwelling driven by a secondary circulation cell whose major role in ventilating and draining the Greenland Sea deep and bottom waters has been largely underestimated.

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Section: Changes In Air-sea Heat Exchangessupporting

confidence: 52%

Section: 1029/2018jc014249mentioning

confidence: 99%

Section: 1029/2018jc014249mentioning

confidence: 99%

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Draining and Upwelling of Greenland Sea Deep Waters

Somavilla

2019

JGR Oceans

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“…A first driver potentially explaining deeper mixed layer depth for some years is the mechanical energy input (e.g. Duhaut and Straub, 2006;Huang et al, 2006;Elipot and Gille, 2009) related with the wind stress and the surface ocean velocity (the surface ocean velocity effect is generally smaller than The alternative source of convective processes deepening the mixed layer depth in winter is the heat fluxes (mostly latent and sensible heat fluxes in winter in the region following Somavilla et al, 2011). During the simulated period, the extremely cold and dry winter in 2005 (Somavilla et al, , 2011(Somavilla et al, , 2016 explains the deepest average mixed layer depth over the domain.…”

Section: Discussionmentioning

confidence: 99%

Interannual evolution of (sub)mesoscale dynamics in the Bay of Biscay

Charria¹,

Theetten²,

Vandermeirsch³

et al. 2017

Ocean Sci.

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Abstract. In the north-east Atlantic Ocean, the Bay of Biscay is an intersection between a coastal constrained dynamics (wide continental shelf and shelf break regions) and an eastern boundary circulation system. In this framework, the eddy kinetic energy is 1 order of magnitude lower than in western boundary systems. To explore this coastal complex system, a high-resolution (1 km, 100 vertical sigma layers) model experiment including tidal dynamics over a period of 10 years (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010) has been implemented. The ability of the numerical environment to reproduce main patterns over interannual scales is demonstrated. Based on this experiment, the features of the (sub)mesoscale processes are described in the deep part of the region (i.e. abyssal plain and continental slope). A system with the development of mixed layer instabilities at the end of winter is highlighted. Beyond confirming an observed behaviour of seasonal (sub)mesoscale activity in other regions, the simulated period allows exploring the interannual variability of these structures. A relationship between the winter maximum of mixed layer depth and the intensity of (sub)mesoscale related activity (vertical velocity, relative vorticity) is revealed and can be explained by largescale atmospheric forcings (e.g. the cold winter in 2005). The first submesoscale-permitting exploration of this 3-D coastal system shows the importance of (sub)mesoscale activity in this region with its evolution implying a potentially significant impact on vertical and horizontal mixing.

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“…Behrenfeld et al (2006) suggested a general trend has occurred of decreased convective mixing, increased stratification and consequent decrease in production in the Northeast Atlantic from 1999 onwards and predicts a decrease in productivity in a warming ocean. There has been a progressive warming of surface waters in the Bay of Biscay over the last 30 years (Garcia-Soto et al 2002, Somavilla et al, 2011Holt et al 2012;Taboada & Anadon, 2012, Garcia-Soto & Pingree, 2012. Winter mixing was studied extensively in Pingree & New (1989).…”

Section: Introductionmentioning

confidence: 99%