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Observing system depiction of circulation in the SE US coastal ocean H. Seim, University of North Carolina at Chapel Hill L. Leonard, University of North Carolina at Wilmington F. Bingham, University of North Carolina at Wilmington M. Fletcher, University of South Carolina D. Savidge, Skidaway Institute of Oceanography C. Edwards, University of North Carolina at Chapel Hill
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Why a circulation climatology? In general: Simple characterization of existing data Important source of validation for models Motivate archival scheme For the SE United States coastline: Confirm existing depictions and develop digital form Examine adequacy of observing system design
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Hare et al., 2007 A specific interest – design of Marine Protected Areas – are they connected?
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Winter/SpringSummer Fall Depiction of Seasonal Cycle by Lee, Yoder and Atkinson (1991), Based on big DOE-funded deployments in ‘70s and ‘80s Distinguishes 3 shelf regimes, inner ( 40m), And the Gulf Stream. Cartoon depicts Gulf Stream, outer and mid shelf. Only variability
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Blanton et al. 2004 – digital model climatology, forced by mass field and climatological winds (COADS) – inner shelf regime hard to distinguish
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Observing System measurement locations (for SABSOON, Caro-COOPs, CORMP, NCCOOS and NDBC) 19 stations occupied between 2000-2007, inner and mid-shelf Area under study In this talk
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Coverage over time in the ‘climatology’ for ADCPs– only months with 50% or greater coverage are included
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20 cm/s 15 50 Small mean flow S of Cape Fear GS influence obvious on 40 m isobath Topographic steering Cape Fear Depth-averaged mean flow
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Wintertime Similar to mean Reasonable comparison to model 20 cm/s Depth-averaged flow
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Summer Whole shelf in motion to NE Minimum flow off SC – signature of gyre? Model underestimates inner shelf flow SC Depth-averaged flow 20 cm/s
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Fall Reduced flow at 40 m isobath Southward flow on middle, inner shelf Minima off SC again Schematic captures flow well Model misrepresents inner, middle shelf SC Depth-averaged flow GA
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SSW Climatological along-shore monthly mean wind (scaled 1cm/s:1m/s) MONTHLY MEAN ALONG- AND CROSS-SHORE CURRENT NNEOn- shore Off- shore ALONG CROSS Depth (m above bottom ) At Station Off GA
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Depth (m) 20 cm/s Depth-resolved flow - February Generally little vertical structure Exception at nearshore stations
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Depth-resolved flow - July 20 cm/s Depth (m) Significant veering Consistent with upwelling Should promote nutrient delivery from GS Exception at shallow stations off SC SC
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Depth-resolved flow - December 20 cm/s Depth (m) Confused flow, strongly divergent Veering mostly in opposite sense Offshore bottom flow – convection?
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40 cm/s Jan
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40 cm/s Feb
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40 cm/s Mar
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40 cm/s Apr
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40 cm/s May
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40 cm/s Jun
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40 cm/s Jul
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40 cm/s Aug
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40 cm/s Sep
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40 cm/s Oct
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40 cm/s Nov
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40 cm/s Dec
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Summary Assembled ADCP observations largely confirm qualitative depiction of Lee et al (1991) – reduced flow off SC consistent with gyre influence but gyre not represented in observations. Digital climatology of Blanton et al (2004) fails to represent inner shelf and equatorward mid-shelf flows Strong upwelling circulation in summer is evident Downwelling circulation present in fall/winter/spring but not shelf-wide Plan to continue assembly of currents and winds, temperature and salinity measurements
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