Science Advisory Report  2014/050

Oceanographic conditions in the Atlantic zone in 2013

Summary

• Sea-surface temperatures were at record highs in September 2013 on the Grand Banks, and generally above-normal during ice-free months across the zone.
• Sea ice volume rebounded somewhat but remained low in the Gulf of St. Lawrence with the 6^th lowest volume since 1969, and decreased on the Newfoundland–Labrador (NL) Shelf to the 4^th lowest value since 1980. Almost no sea-ice was exported to the Scotian Shelf for the fourth consecutive winter.
• The Gulf of St. Lawrence Cold Intermediate Layer (CIL) was colder and thicker in 2013 than the record conditions (since the 1980s) of 2012, but was still generally thin and warm, similar to conditions of 2011. The Scotian Shelf CIL volume was near-normal (-0.4 SD) after a series record low in 2012, while on the Newfoundland and Labrador Shelves the CIL was mostly thinner than in 2012 with area anomalies ranging from -0.5 to -1.4 SD. While conditions were bimodal in 2012, being near-normal on the Newfoundland and Labrador Shelves and at record thin levels in the Gulf and on the Scotian Shelf, conditions were more uniform across the zone in 2013 with below-normal areas and volumes (i.e. warm conditions).
• Bottom temperatures were generally above-normal across the zone, but down from record highs of 2012 recorded in the northern Gulf at shallow depths and in parts of the Scotian Shelf. A series record high was however recorded in the northern Gulf in deeper waters (>100 m, +2.0 SD) associated with a warm anomaly first observed in Cabot Strait in 2010 that is propagating toward the heads of channels.
• The most widespread negative anomalies in surface (0-50 m) and subsurface (50-150 m) nitrate inventories of the time series were seen in 2010-2011. The relatively consistent recovery in nutrient inventories seen across most parts of the Scotian Shelf and Gulf of St. Lawrence in 2012 continued in 2013. In contrast, both surface and subsurface inventories of the Newfoundland–Labrador Shelf and Grand Banks were below normal, with the subsurface inventories deepening the decline that started in 2009.
• Chlorophyll inventories were near the long-term average throughout much of the Atlantic Zone in 2013.
• In 2013, zooplankton abundance indices demonstrated relatively large scale coherence. Copepod abundance on the Eastern Scotian Shelf and in the southern Gulf of St. Lawrence was below average in 2013 and had declined relative to 2012, whereas abundance was above normal across most of the Newfoundland Shelf.
• There have been notable changes in the phylogeny of key zooplankton taxa in both the Gulf of St. Lawrence and on the Newfoundland Shelf. On both regions, the period of maximum contribution of young (CI–III) and later (CIV-CV) copepodite stages have progressed toward occurring earlier in the summer, a change which appears to have started in 2006.

This Science Advisory Report is from the March 18-20, 2014 Sixteenth Annual Meeting of the Atlantic Zone Monitoring Program (AZMP). Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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