Synthetic Float Analysis in HYCOM Synthetic floats were released in an ocean model to study how the upper-limb (northward return flow) of the Atlantic meridional overturning circulation crosses the equator and flows to high northern latitudes An animation of a subset of the released synthetic floats is presented in the file floats_carib_all.avi Background information for this animation is presented in the subsequent slides

Properties of the HYCOM Simulation Model Domain and Grid –Atlantic Ocean, 30S to 70N –1.4 degrees horizontal resolution –25 vertical layers Forcing –NCEP/DOE reanalysis climatology Some Model Properties –KPP vertical mixing –Simple energy loan ice model –Surface S relaxation to climatology –Relaxation b.c. at north and south 30-year Spinup from Climatology 10-year Simulation with Synthetic Floats

Synthetic Float Experiment Synthetic Floats –Advected by 3-D Velocity Field –Interpolation to Float Space – 2 nd order polynomial Time – 4 th order Runga-Kutta Southern Hemisphere Release Experiment –7200 Floats Released Domain –5-14S, 28-32W Horizontal Resolution –1 degree in both longitude and latitude Depths –12 depths »25 to 300 m at 25 m intervals Release Times –Monthly during the first year of the 10-year integration »600 per month

The Animation Of the 7200 floats released in the southern hemisphere, 2646 eventually entered the Caribbean Sea during the 10-year integration Floats entering the Caribbean represent fluid particles that flow from the southern hemisphere into the North Atlantic subtropical gyre flow to eventually reach high latitudes. Selection of this subset of floats clearly illustrates pathways of the upper limb of the MOC The animation is contained in the file floats_carib_all.avi –The depth of each float is indicated by color

Reference Scientific details are contained in the paper “A Synthetic Float Analysis of Upper-Limb Meridional Overturning Circulation Interior Ocean Pathways in the Tropical/Subtropical Atlantic” by Halliwell, Weisberg, and Mayer It is available on the HYCOM web page hycom.rsmas.miami.edu under “publications”