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Long-Term Ocean Climate Observations (LOCO)

 

IRMINGER SEA

 

From the Gulfstream system warm and saline water enters the sub-arctic North Atlantic Ocean. There its properties change due to air-sea interaction. Sub-Arctic Mode Water (SAMW) is progressively formed in the cyclonic gyre of the North Atlantic Ocean by convective mixing in successive winters. One of the last stages of SAMW is found in the centre of the cyclonic sub-gyre in the Irminger Sea. Evidence is growing that in this ocean region occasionally deep convection occurs which homogenizes the water column to a depth of nearly 2000m. The heat, released to the atmosphere during the transformation of Gulfstream water to the much cooler SAMW is an important factor for the North Atlantic climate.

 

Annual hydrographic surveys during the WOCE and CLIVAR programmes as well as satellite altimetry have shown that the inter-annual and seasonal variability of the hydrography in the Irminger Sea are of the same order of magnitude. Eddy variability is definitely smaller. How these different types of variability interact, and how convective mixing in winter depends on this variability is not well known. Therefore Royal NIOZ started a monitoring programme with moored sensors in the summer of 2003. At three positions in the Irminger Sea near the annual WOCE-CLIVAR section, moorings fitted with a profiling CTD and with ADCPs will monitor the varying hydrographic structure from 2003 until at least 2008. Together with two profiling moorings from Woods Hole Oceanographic Institution and a European ANIMATE mooring the LOCO moorings will contribute to a pre-operational monitoring programme in the Irminger Sea.

 

ADCP

Near the central mooring site a sediment trap mooring has also been deployed to monitor the downward particle flux for 5 years. This will allow to determine the relation between climatic variability of the hydrography and the near bottom particle flux towards the sediment. from 2003 to 2004 additionally a internal wave array was deployed in the Irminger Sea.

 

 

Fig. The bathymetry of the Irminger Sea with depth contours every 500 m. The straight line shows the WOCE/CLIVAR section along which since 1990 until present nearly annually hydrographic surveys have been carried out. The red dots show the mooring locations and the four easternmost moorings form the internal wave array.

 


List of Research Cruises:

 

         North Atlantic Ocean [ D332 ] (Irminger Sea)

(Note: combined LOCO/VAMOC cruise)

- RRS Discovery (August/September 2008)

 

         North Atlantic Ocean [ D309/310 ]

- RRS Discovery (August/September 2006)

 

         North Atlantic Ocean [ 64PE240 ]

(Note: combined BSIK/CAMP/LOCO/CIS cruise)

- RV Pelagia (September/October 2005)

 

         North Atlantic Ocean [ CD163/164B ]

- RRS Charles Darwin (September/October 2004)

 

         North Atlantic Ocean [ 64PE216 ]

- RV Pelagia (August/September 2003)