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Results from the LOCO mooring: 2003-present

Results from the LOCO mooring: 2003-present. M. Femke de Jong, Hendrik M. van Aken , Geert-Jan Brummer , Lukas Jonkers , Laura de Steur. Mooring(s). LOCO (NIOZ Fys ) 2: Sept 2003 – present 3: Sept 2003 – Sept 2008 PIs: H.M. van Aken , M.F. de Jong. Presently L. de Steur .

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Results from the LOCO mooring: 2003-present

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  1. Results from the LOCO mooring: 2003-present M. Femke de Jong, HendrikM. van Aken, Geert-Jan Brummer, Lukas Jonkers, Laura de Steur

  2. Mooring(s) LOCO (NIOZ Fys) 2: Sept 2003 – present 3: Sept 2003 – Sept 2008 PIs: H.M. van Aken, M.F. de Jong. Presently L. de Steur. IRM (NIOZ Geo) Sept 2003 – Aug 2007 PIs: G.-J. Brummer, L. Jonkers

  3. Location: bathymetry Moored at approx. 3 km isobath. Near AR7E section. Under Greenland tip jet. LOCO2 close to CIS mooring (~30 nm).

  4. Location: Currents In agreement in top part of water column. Lavender et al., 2000

  5. Velocities Mean velocities Mooring blow down

  6. Influence of bottom topography

  7. Location: hydrography LOCO 2 Top in most weakly stratified part. Bottom in DSOW. LOCO 3 Top closer to Irminger Current.

  8. Results GEO Shown: mean annual cycle from 3 years of sediment trap data. • Blooms are species specific. • Light and temperature driven. Start as mixed layers shallow. Also visible in LOCO ADCP backscatter intensity. Jonkers et al., 2010

  9. Results LOCO: Deep waters Bottom microcats

  10. Local deep mixing Generally mixing within SPMW layer. Down to 1000 m during strong: • winter cooling • preconditioning OAflux: 2008: 279 W m-2 2009: 157 W m-2 2003-2010: 155 W m-2 de Jong et al., 2012

  11. Mixed waters It’s becoming quite clear that deep mixing takes place throughout the western Subpolar Gyre. (Pickartet al., 2003; Vågeet al., 2008; de Jong et al., 2010). Likely important as first stage in the formation of “classical LSW”. Exact volume unknown…

  12. Lateral scales of mixing Area involved with mixing potentially stretches out further north. Example: Jan 2012 Section from combined Argo profiles: Weak stratification extends north due to compensating salinity.

  13. Focus on coolingBut what about warming? Net surface heat flux is cooling the basin. 2002 to 2012: 25 W m-2. Would result in temperature change of -0.1 ˚C/year. Observed +0.03 ˚C/year. Import of heat by eddies? Fan et al., 2013.

  14. Interest in OOI • Extend time series and/or combine with CIS/LOCO. • Get lateral data on mixing extent & scales. • Get data on eddies / lateral heat flux. • Links with biology.

  15. Additional slides: Data recovery LOCO 2 & 3 • ADCPs: generally full data sets. • SBE37: T,S okay. Some broken P-sensors. • MMP: daily profiles, 21% to 98% of max. Instrument can become “stuck” due to biofouling. IRM Sediment traps • tilt generally < 2˚, max 6˚. • 19 / 16 day samples. (Local core sampling problematic)

  16. Scales of mixing Restratification occurs during the convective season as well as in spring/summer. And/or small mixing cells moving around.

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