THOR Annual MeetingTHOR Annual Meeting

Paris, 24 November 2009Paris, 24 November 2009

Nuno Nunes,Nuno Nunes,

Jürgen Fischer,Rainer Zantopp, Martin VisbeckJürgen Fischer,Rainer Zantopp, Martin Visbeck

Recent changes in properties andRecent changes in properties and

transport in the Labrador Seatransport in the Labrador Sea

GreenlandScotland Ridge

O

erfl

Ve

ntila

tion

Compensating flow

v

OverflowWater 0°C

6 Sv

NADW 3°C16-18 Sv

6 Sv

Mixing 12 Sv

Arctic

CoolingLowlatitude

En

train

me

nt

6°CL

ab

rad

or S

ea

Ve

nt.: 4

-6 S

v

Up-welling

Surface outflow 3 Sv

Fresh-water

Atlantic inflow

ow

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 operationsMaria 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

K8

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 1997- July 1997 only

1999-2001: 2 moorings

2001-2003: 3 moorings

2003-2005: 1 mooring

2005-2007: 1 mooring

2007-2009: 3 moorings

2009-2011: 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

WBC at 53°N

THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck

LS Boundary Current Data1.Two years with full array2.10 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 + Errortime series

WBC at 53°N

THOR Annual Meeting – Paris 2009 – Nunes/Fischer/Zantopp/Visbeck

EOF‘s 1997-1999•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