Atmospheric conditions associated with oceanic convection in the south‐east Labrador Sea

Abstract

[1] It has been speculated that low-level reverse tip-jets, caused by the interaction of synoptic-scale atmospheric flow and Greenland, are an important mechanism for forcing open ocean convection in the south-east Labrador Sea. Here float data and meteorological reanalysis fields from the winter of 1996/1997, in combination with a simple mixedlayer ocean model, are used to show that, although relatively deep ocean convection did occur during this winter, the primary forcing mechanism was cold-air outbreaks from the Labrador coast rather than the smaller scale reverse tip-jets. During this winter, the North Atlantic Oscillation (NAO) was in a weak positive phase. Similar treatments of the winters of 1994/1995 (strong, positive NAO) and 1995/1996 (strong, negative NAO) suggest that the result is robust regardless of the state of the NAO.

Surprising return of deep convection to the subpolar North Atlantic Ocean in winter 2007–2008

“…As seen in Figure 5a, the wind vector anomalies in 2006-07 were generally from the east throughout most of the Labrador Sea. Furthermore, the anomaly pattern in the vicinity of southern Greenland for that winter is consistent with an atmospheric flow regime known as the reverse Greenland tip jet 23 , which typically does not lead to deep mixing 24 .…”

Multi‐event analysis of the westerly Greenland tip jet based upon 45 winters in ERA‐40

“…Hence modification by air-sea interaction in the Labrador Sea is somewhat reduced, and, as shown in section 5, tip jets are very effective at extracting heat from the southwestern part of the Irminger Sea. A marked difference in origin of the air comprising the westerly and easterly tip jets is likely a major reason why the latter is not believed to cause deep oceanic convection in the southeastern Labrador Sea (Sproson et al, 2008). Figure 7 also demonstrates that most of the trajectories curve around Greenland, suggesting that acceleration by deflection is a key mechanism of tip jet generation (e.g.…”

Argo - A Decade of Progress

“…This was a surprise after a decade of much less intense convection. The relation of the onset of convection in the Labrador Sea to atmospheric conditions is described by [38] and the implications of these surprising observations was reviewed by [39].…”