NODC ELECTRONIC DATA DOCUMENTATION FORM

Contributor Identification

John Reager
University of Delaware College of Marine Studies
102 Robinson Hall
Newark, DE 19716
USA
(302) 831-1194
jreager@udel.edu

Data Collector Identification

Dr. Richard Garvine
University of Delaware College of Marine Studies
Newark, DE 19716
(302) 831-2169
rgarvine@udel.edu

Dr. Charles Tilburg
University of Georgia
Athens, Georgia
tilburg@uga.edu

Dataset Title

DECADE PROJECT/Drifters/2003/Survey1-0304

Dataset Abstract

ftp://ftp.cms.udel.edu/pub/users/tilburg/data/DECADE/Drifters/2003/README

Dataset Purpose

Project Summary 
Discovering the primary processes that control across-margin transport of biologically, geologically, and chemically important materials has first rank priority in ocean science. A major component of this across-margin transport is the result of freshwater inflow from rivers and estuaries into the coastal ocean. The  evidence  to  date  from  model  studies  and  field  observations  is  that  coastal  Ekman  circulation, especially  upwelling  circulation,  is  the  most  effective  mixing  agent.  Consequently,  we  focus  on  this agent.  We  offer  four  related  hypotheses:  1)  During  upwelling,  the  offshore  advection  of  near  surface buoyancy or fresh water by the surface Ekman flux induces rapid vertical mixing of the fresh water with ambient shelf water.  2) The total mixing of plume water with ambient shelf water during upwelling wind events  exceeds  that  for  downwelling  events  of  the  same  magnitude.  3)  During  upwelling,  the  mixing action is concentrated at the offshore edge of the plume. 4) The mixing dynamics there is principally a balance between offshore advection of buoyancy or fresh water by the upwelling Ekman transport and vertical diffusion between buoyant water of the plume with the saltier ambient shelf water below.    The overall objective of this project is to determine the major elements in the mixing dynamics and the  circulation  in  a  buoyant  coastal  plume  during  upwelling  and  downwelling  circulation  events. 
Particular objectives are: 1) Compare mixing mechanisms during upwelling and downwelling events. 2) Find and compare the peak levels of vertical mixing in space for both upwelling and downwelling events. 3) Find and compare the bulk level of vertical mixing for the plume as a whole during both upwelling and downwelling  events.  4)  Find  the  level  of  vertical  diffusivity  (Kz)  during  both  events.  5)  Diagnose  the advective-diffusive  balance  for  buoyancy  near  the  plume  surface  during  both  events.    6) advance  the capability in numerical modeling of circulation and mixing in buoyant coastal plumes.     The project has three closely related elements: 1) field observations that include a moored array of instruments, purposeful dye tracing, and rapid shipboard surveys of the buoyant plume hydrographic and current fields, 2) numerical model studies of mixing processes in buoyant plumes, and 3) analysis and synthesis of the field data and model results.  We propose the use of new technology in the field work. We will conduct purposeful injection of a fluorescent dye as a tracer. It is able to measure 3-dimensional Lagrangian circulation and mixing.  We will also use another new method, called the variance method, a technique for recording and processing ADCP  data  that  yields  direct  measurement  of  turbulent  Reynolds  stresses  and  similar  turbulence quantities.  The  injection  and  subsequent  dispersion  of  dye  within  the  coastal  circulation will  be  reproduced using numerical simulations. The combination of field measurements and numerical simulations allows an  unprecedented  opportunity  to  evaluate  different  turbulence  closure  schemes  within  the  numerical model, especially as they pertain to the highly stratified flow conditions on the shelf.   The particular subject of the field and model studies is the Delaware Coastal Current. We selected this  system  because  it  is  of  intermediate  scale  among  buoyant  coastal  discharges  and  because  it  is logistically opportune. 

Dataset Collection dates

drifters deployed from 2003-04-14 to 2003-04-16

Dataset Location

Middle Atlantic Bight continental shelf / offshore Delaware Bay: 
drifter drop (Lon,Lat) = (-74.91, 38.60)

Instruments Used

(3x)Horizon Drifter using ARGOS system for location,
(1x)Brightwater Drifter using ARGOS system for location
(1x)Brightwater Drifter using GPS-ARGOS system for location

Parameters measured

Yearday/Hour/Minute,	Lon/Lat

Project Name

DECADE project - Survey1- drifters

File names

arg02873.dat, arg02877.dat, arg02887.dat, arg27105.dat, GPS27105.dat

Scientific Content of Dataset

The format for GPS?????.dat files is the following:
Month Day Year Hour Minute Second Longitude Latitude 

The format for arg?????.dat files is the following: 
Longitude Latitude YearDay Hour Minute 

All times are in UTC. The first entry is the time and location of the deployment. The last entry is the time and location of the recovery. Note that YearDay 104 = April 14. 

I edited the data to remove obviously spurious data and included only those locations that corresponded to the actual sampling period, not during times when the drifter was at Lewes or aboard the ship. 

Data Format of Dataset

FTP site: 
ftp://ftp.cms.udel.edu/pub/users/tilburg/data/DECADE/Drifters/2003/

see "README"

CONTACT:
JT Reager
jreager@udel.edu
(302) 831-1194
102 Robinson Hall
Newark, DE 19716

Relevant Publications

Houghton, R.W., C.E. Tilburg, R.W. Garvine, A. Fong, 2003. Delaware River Plume Response to a Strong Upwelling-Favorable 
	Wind Event. Geophysical Research Letters, in submission.