Transcript Powerpoint file - Oregon State University

Interaction of a Dye Tracer
with an Upwelling Front
during Variable Winds
Andy Dale, Jack Barth, Murray Levine,
Steve Pierce (COAS, Oregon State University)
Jay Austin (Old Dominion University)
NSF funded 2002-2004
With thanks to ….
Murray Stein and crew of New Horizon
Dennis Root (dye hardware etc.)
Anatoli Erofeev (visualization software)
Cambria Colt (Scripps res. tech.)
Help at sea ….
Said Ahmed
Allan Book
Renato Castelao
Anthony Kirincich
Larry O’Neill
Bob O’Malley
Michael Ott
Inspiration ….
Houghton, Ledwell etc.
Collaborations with ….
Tim Cowles’ group (bio-optical profiler/thin layers)
Minibat
Offshore Ekman
transport
Frontal region
What happens to this dye patch during an
upwelling-relaxation cycle??
Dye released as an
alongshelf streak on
a density surface…..
1 knot
Weighted
Minibat
~1 km
Minibat and dye diffuser
Minibat survey …..
Drogued
ARGOS/GPS
drifter
6-7 knots
Shipboard ADCP
Also CTD tow-yos at ~ 1 knot
Dye tanks and plumbing
Dye release 1 (fluorescein)
Dye release 2 (rhodamine)
46029
NOAA buoy 46029
Release 2
100 m
Upwelling
Downwelling
Release 1
NOAA buoy 46050
46050
OREGON
R/V New Horizon
Dye 1 - Fluorescein
ADCP velocity at 16m
START
Dye patch
released.
Size of dye patch 20
hours after release
~ 1.5km x 3.5 km
Dye
advects
south at
~0.6 m/s
FINISH
Survey of dye patch 20-25
hours post-release.
1 km
0.5 m/s
Ekman
Transport
~0.20 m/s
Plots
centered
on 120m
isobath
Wind at buoy 46050
Release
20 hours after release
Wind at buoy 46050
Release
23 hours after release
Wind at buoy 46050
Release
23.5 hours after release
Wind at buoy 46050
Release
24 hours after release
Wind at buoy 46050
Release
24.5 hours after release
Wind at buoy 46050
Release
34 hours after release
1
4
?
2
3
5
Mean and standard deviation of fluorescein density
Entrainment to
mixed layer
Continued
entrainment of
dye-free water
Dye 2 - Rhodamine
33 hours after release
Orange bar shows an inertial period
Release
43.1 hours after release
Release
62.6 hours after release
Release
Density
Temperature
Salinity
Rhodamine
Mean and standard deviation of rhodamine density
Entrainment
Relaxation/
restratification
Conclusions
 During strongly upwelling-favorable winds, steepening
of isopycnals combined with wind-induced mixing
generates a surface mixed layer which actively entrains
water beneath an upwelling front.
 When upwelling-favorable winds cease or reverse,
restratification is rapid with water from the frontal zone
becoming widely distributed across the shelf.
Plus …
 These dye releases have revealed other interesting
phenomena not covered here ….
10
20
30
Tow-yo section with bifurcated dye patch …
16 hours after
release
Density
Temperature
Salinity
Rhodamine
Tow-yo section with internal wave train …
13.9 hours
after release