Observations of Mesoscale* Ocean

Circulation: Present and Future

Observations of Mesoscale* Ocean

Circulation: Present and Future

Bo QiuDept of Oceanography University of Hawaii

Bo QiuDept of Oceanography University of Hawaii

A UH profiling float was being deployed from R/V Revelle in Kuroshio Extension, May ‘05

Schematic of Satellite Altimetry

* mesoscale = 10s~100s km

* mesoscale = 10s~100s km

Altimeter-derived rms sea surface height variability (cm)

Eddy “desert

”

Abundant mesoscale eddies

Altimeter-derived rms sea surface height variability (cm)

Schematic of NW Pacific Ocean Circulation

Semi-monthly Kuroshio Extension paths (1.7m SSH contours)

Stable yrs: 1993-94, 2002-04

Unstable yrs: 1996-2001, 2006-07

(a) Upstream KE path length (141-153°E)

(b) Eddy kinetic energy (141-153°E, 32-38°N)

Stable yrs: 1993-94, 2002-04

Unstable yrs: 1996-2001, 2006-07

Pacific Decadal Oscillations (Mantua et al. 1997)Pacific Decadal Oscillations (Mantua et al. 1997)

• Center of action of wind forcing is in the eastern half of the N Pacific basin

• Positive (negative) phase of PDO generates – (+) local SSH through Ekman divergence (convergence)

Yearly SSH anomaly field in the North Pacific Ocean

+

-

2004 stable

2005 unstable

20 floats 28 floats

UH-KESS profiling float measurements

1500db5 days

Kuroshio Extension System Study Observing Array/Timeline

Kuroshio Extension System Study Observing Array/Timeline

Distributions of semi-monthly profiling float T/S

data

(contours: SSH from satellite altimeters)

T(z) and PV(z) evolution in the KE recirculation gyre

mixed layer depth

subtropical mode water

KESS period

PV values on 25.4 σθ surface (~250m)

from mesoscale to submesoscale …from mesoscale to submesoscale …

What’s Next ?What’s Next ?

SSH snapshot from the NLOM model for 04/10/2006Right: from the original 1/32°-resolution output

Left: reduced to 1/2°-resolution (observable by current nadir-looking satellite altimeters)

SSH vs vorticity snapshot from the NLOM model for 04/10/2006

original 1/32°-resolution reduced 1/2°-resolution

original 1/32°-resolution

anticyclonic vorticity

cyclonic vorticity

PDF of modeled vorticity as a function of intensity

Ratio of anticycl./cyclonic vorticities

Recommended to NASA by the NRC Decadal Survey for Oceanographic and Hydrological Applications:

http://bprc.osu.edu/water

1. Point vs 200km-wide swath measurements

2. Repeat cycle: 10 days vs 3~5 days (at mid-high lat.)

“Surface Water and Ocean Topography (SWOT)” Mission

“Surface Water and Ocean Topography (SWOT)” Mission

Approximate Time and Space Scales of Oceanic Variability

Chelton (2001)

center of PDO

forcing

L

H

L

EKE level

SSHA along 34°N

SSH field

PDO index

145E 165E155E135E

Yearly-mean sea surface height field

Kuroshio Extension System Study (KESS) is designed to study KE’s transition/impact from a stable to unstable

state

KESS period

T(z), S(z) and PV(z) evolution in the KE recirculation gyre

mixed layer depth

subtropical mode water

Altimeter-derived rms sea surface height variability (cm)

Schematic of NW Pacific Ocean Circulation

Eddy “desert

”

Abundant eddies