Water Mass Variability in the Labrador Sea

The Labrador Sea is important to the global and regional climate systems because:
  1. wintertime cooling can result in deep convection to depths of 1000-2400m there,
  2. it is a receiving region for Arctic outflow, and
  3. it influences the Labrador Current and hence downstream regions.

The deep convection results in the intermittent formation of an important intermediate-depth water mass called Labrador Sea Water (LSW) which contributes to the lower limb of the Atlantic Meridional Overturning Circulation (AMOC) (sometimes referred to as the "global ocean conveyor belt"). This is important in the transport of carbon dioxide, heat and freshwater in the coupled atmosphere-ocean climate system.

In conjunction with AZOMP, scientists in OSD are investigating the variability of various water masses in the Labrador Sea, and their inter-relation with upstream and downstream variability in the AMOC and on the Atlantic Canadian shelf and slope

An important finding has been that there can be large interannual variability in the deep convection and formation of Labrador Sea Water, apparently related to atmospheric forcing.

Temperature distribution on the AR7W line
Temperature distribution on the AR7W line showing remnant Labrador Sea Water (LSW2000) from the early 2000s in spring 2007, and a newly-formed class of Labrador Sea Water (LSW2008) in spring 2008.
Time evolution
Time evolution of the vertical structure of temperature in the central Labrador Sea since 1970, based on the AR7W and earlier surveys. There is large decadal-scale variability associated with the intermittent formation of LSW.

The importance of LSW to global climate change is discussed in Chapter 5 (p.396) of the Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC).

For further information on related ocean monitoring, see Physical Oceanographic Monitoring of the Labrador Sea

For further information on the formation of LSW in winter 2008, see Yashayaev and Loder (2009).

For further information, contact Dr. Igor Yashayaev.


Yashayaev, I. 2007. Hydrographic changes in the Labrador Sea, 1960-2005. Progress in Oceanography, Vol.73, No. 3-4, 242-276. doi:10.1016/j.pocean.2007.04.015.

Yashayaev, I. and J.W. Loder. 2009. Enhanced production of Labrador Sea Water in 2008. Geophysical Research Letters, 36, L01606, doi:10.1029/2008GL036162.