Scope of activities

Cascading (or shelf convection) is a type of density-driven current, in which dense water is formed over continental shelves due to cooling/freezing events and descends down the slope to a greater depth (Shapiro et al., 2003, Ivanov et al, 2004) (see figure 1).  

Figure 1 - Cascading water formation

Alongside with open ocean deep convection, cascading contributes to the renewal of deep waters and the Meridional Overturning Circulation. Cascading is thought to be one of the major players in shelf-ocean interaction in the Arctic Ocean and to contribute to carbon export from continental shelves to the open ocean. Hence, it might influence the long-term sequestration of the carbon drawn-down from the atmosphere by biological production in shelf seas, with consequences for global climate (Huthnance et al., 2009, Holt et al., 2009). However because it is an episodic process, happening in winter time, it is difficult to observe. Recent modelling studies (Ivanov et al., 2015) suppose the existence of cascading events in the Laptev Sea, both sides of Greenland (Pickart et al., 2005; Marson et al., 2017) and in many locations around in the Arctic and Antarctic. Signatures of cascading processes have been found in observations: e.g. Aagard et al., 1981; Middtun, 1985; Quadfasel et al., 1988; Melling, 1993; Schauer, 1995; Weingartner et al., 1998; Schauer, and Fahrbach, 1999; Haarpaintner et al., 2001; Ivanov et al., 2004; Ivanov and Shapiro, 2005; Ivanov and Golovin, 2007, etc.

This team will use models with different vertical and horizontal resolutions on a multi-decadal time scale and observations to address the following problems:

  • Define cascading processes and their representation in models. Evaluate uncertainties and sensitivity of cascading processes representation in models to vertical and horizontal grid, vertical turbulent schemes, horizontal mixing, etc.;
  • Create the first ensemble model based database of cascades, evaluate vertical and cross–shelf dense water fluxes;
  • Identify the key locations on the Arctic shelves, where cascading is the most probable. Test it versus observations;
  • Examine the most important physical mechanisms driving cascading: relation with summer ice decline, atmospheric forcing (e.g. Arctic Ocean Oscillation), examine its temporal and spatial variability;
  • Clarify the role of cascading in deep water mass formation, carbon storage and climate change.

References


Team leaders

Paul Myers
University of Alberta

Maria Luneva
NOC Liverpool, UK


Accomplishments

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Questions?

Contact Andrey Proshutinsky, Senior Scientist, Woods Hole Oceanographic Institution at aproshutinsky@whoi.edu.