The Loop Current Dynamics Study: Overview and Preliminary Results Peter Hamilton Science Applications International Corporation Raleigh, North Carolina Science Team Dr. Peter Hamilton – SAIC Moored current data analysis Dr. Kathleen Donohue & Dr. Randy Watts – URI PIES data analysis Dr. Robert Leben – University of Colorado (CCAR) Satellite data analysis Dr. Leo Oey – Princeton University Dr. D-P Wang – State University of New York Numerical modeling & syntheses Field Logistics and Chief Scientist: James Singer – SAIC 2 Key Program Objectives • Overall objective is to increase our knowledge of the dynamics of the Loop Current in the Gulf of Mexico through analysis and synthesis of observations and numerical modeling output. • The synthesis of results and model predictions is key! Major Objectives: . Upstream and Downstream Influences . Upper to Lower Layer Coupling . Lower-Layer Eddies and TRWs . Dynamics of Eddy Shedding . Role of Peripheral Cyclones . LC Variability 3 Process Investigations • Determine upper- and deep-layer vorticity budgets. • Diagnose the stream-coordinates-mean velocity and potential vorticity structure of the LC. • Quantify the eddy-mean exchanges of momentum and energy in the mean and in energetic events. • Conduct case-studies of the major eddy events and diagnose their kinematics and three-dimensional evolution. 4 Loop Current Dynamics Array & CICESE’s Arrays Deployment: April 2009 Rotation: July & Nov 2010 Retrieval: November 2011 5 Tall Mooring Instrument Placement 6 Maximum Loop Current Velocity Profiles and Tall Mooring Velocity Measurements 7 Tall Mooring Upper Layer T/S/P Measurements 8 Short Mooring Schematic 9 LC Variability & Array Location 10 Historical LC Separation Locations 11 Most Probable LC Location 12 One PIES provides point measurements supporting: • T(p,t),S(p,t), dynamic height(t) • Bottom pressure anomaly • Total sea surface height – steric + mass loading 13 An Array of PIES Maps 3-D Circulation • Map T,S, dynamic height • Map baroclinic geostrophic velocities • Level pressure • Map absolute geostrophic circulation • Map mean sea surface height 14 Modeling Component • Dynamical Interpretations • Upstream/Downstream Dynamics and Influences • Model/Observation Synthesis • Long-period Remote Regional Coupling 15 Model Domain 16 Preliminary Results Deployment 1: April 2009 to July 2010 Data Return : ~ 93% 17 Mooring Locations 18 A2 40-HLP Currents & Temperature 19 Surface Layer Statistics 20 Lower Layer Statistics 21 Potential Vorticity Constraints on Lower Layer Eddy Formation 22 Movie from PIES 23 Crest-Trough Upper-Lower Layer Coupling – July-Aug 2009 24 Ekman Separation Sequence 1 25 Ekman Separation Sequence 2 26 Hydrocarbon chemistry on 300 water samples (0 to 1,500 m) at 25 PIES sites in the LC in July 2010, analyzed by Texas A&M. No significant concentrations found. 27 Summary Observations so far (15 months): . 9 tall moorings (V,T,S,P) . 6 short moorings (V,T) . 25 PIES (τ,P,T) . Satellite Altimeter (SSH) & Remote Sensing (SST, etc.) Major Events: . Separation of Eddy Ekman (Aug–Sep 2009) . Subsequent northward extension of the LC through array . Formation of Eddy Franklin (April–July 2010) Dynamics: . Development of lower layer cyclones and anticyclones under LC frontal troughs and crests . Mean lower layer cyclone – anticyclone pair under LC . Bursts of lower layer current under advancing LC front 28 .