THOR Annual Meeting Paris, 24 November 2009 Nuno Nunes, Jürgen Fischer,Rainer Zantopp, Martin Visbeck Recent changes in properties and transport in the Labrador Sea

Overturning Circulation in NA THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck

Overview Update on Labrador Sea mooring operations Variability of the WBC at 53°N Central Labrador Sea (K1) temperature timeseries THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck

Mooring operations Maria S. Merian 12/1 (May/June 2009) 4 moorings recovered and re-deployed 2 additional moorings on 53 N array will be serviced again in July 2010 (RV Meteor) THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck

Mooring operations THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck K8K8 K9 K10

Mooring operations THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck K9 drifted for 5 weeks prior to recovery Argo Watchdog allowed us to follow drift path Recovered approx. 75 nm from mooring position 10 out of 12 instruments recovered with full record AR recovered, locked: anchor chain corrosion?

Mooring operations THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck “normal” appearance of recovered chain …and what was left of K10's anchor chain!!!

Mooring operations THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck ?

Mooring operations K9 after 5 weeks adrift A bit of weather... (photo courtesy of T. Wasilewski) THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck

Complete array from June July 1997 only : 2 moorings : 3 moorings : 1 mooring : 1 mooring : 3 moorings : 5 moorings (funded elsewhere) 53°N Present -- DSOW part will be strengthened THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck WBC at 53°N

THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck LS Boundary Current Data 1.Two years with full array 2.10 years reduced coverage Full Array Reduced Array Structure by EOF‘s Expl. Variances Det. of uncertainties regress to EOF‘s Integrate 12 y BC Transport + Error time series

WBC at 53°N THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck EOF‘s Mode 0 – mean flow field Mode 1 – LC-mode with annual cycle Mode 2 – meander mode Mode 3 – BC pulsation Modes for annual subsets very similar! Modes 1-3 explain 80% of the variance

WBC at 53°N THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck

WBC at 53°N THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck

WBC at 53°N THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck

Central Lab Sea temperature THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck

Central Lab Sea temperature THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck Heat flux anomaly (Vage et al., 2008)

Central Lab Sea temperature Convection and bouyancy fluxes Patchy vs. basin- wide convection: connection with depth? What can Argo floats tell us? THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck