Decadal variability in the Indo-Pacific ocean inferred from satellite data and ECCO assimilation...
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![Page 1: Decadal variability in the Indo-Pacific ocean inferred from satellite data and ECCO assimilation Tong Lee NASA Jet Propulsion Laboratory, California Institute.](https://reader034.fdocuments.us/reader034/viewer/2022052608/5a4d1b877f8b9ab0599bd3f4/html5/thumbnails/1.jpg)
Tong LeeNASA Jet Propulsion Laboratory, California Institute of Technology
Michael McPhadenNOAA Pacific Marine and Environmental Laboratory
Decadal variability in the Indo-Pacific ocean inferred from satellite data and ECCO assimilation
Reference for observational part: Lee and McPhaden (2008), GRL, Jan. 15 issue
![Page 2: Decadal variability in the Indo-Pacific ocean inferred from satellite data and ECCO assimilation Tong Lee NASA Jet Propulsion Laboratory, California Institute.](https://reader034.fdocuments.us/reader034/viewer/2022052608/5a4d1b877f8b9ab0599bd3f4/html5/thumbnails/2.jpg)
MotivationLinkages of DecVar of ocean circulation in the Indo-Pacific region not well understood, e.g., the meridional overturning circulations (MOCs) of the two oceans were studied separately (McPhaden & Zhang 2002/2004, Lee 2004).
Approach• Analyze satellite observations of sea surface height (SSH) and ocean
surface wind in the past 15 years; infer ocean circulation changes. SSH: TOPEX/Poseidon (1992-2005) & JASON-1 (2001-present) altimeters; Wind: ERS (1991-2001) & QuikSCAT (1999-present) scatterometers.
• Quantify ocean circulation changes using ECCO (http://www.ecco-group.org) & ECCO-2 (http://ecco2-org, hi-res) ODA products.
![Page 3: Decadal variability in the Indo-Pacific ocean inferred from satellite data and ECCO assimilation Tong Lee NASA Jet Propulsion Laboratory, California Institute.](https://reader034.fdocuments.us/reader034/viewer/2022052608/5a4d1b877f8b9ab0599bd3f4/html5/thumbnails/3.jpg)
Decadal tendencies change sign around yr 2000. SSH in many regions forced by near-local wind (tilted arrows reflect ocean adjustment by Rossby waves)
SSH trend for 1993-2000 (T/P altimeter)
SSH trend for 2000-2006 (T/P,Jason-1 altimeters)
Wind stress curl trend for 1993-2000 (ERS scat)
Wind stress curl trend for 2000-2006 (QuikSCAT)
cm/yr
dyn/cm2/yr
![Page 4: Decadal variability in the Indo-Pacific ocean inferred from satellite data and ECCO assimilation Tong Lee NASA Jet Propulsion Laboratory, California Institute.](https://reader034.fdocuments.us/reader034/viewer/2022052608/5a4d1b877f8b9ab0599bd3f4/html5/thumbnails/4.jpg)
SSH time series (black curves) in key regions further illustrate the tendency change around 2000
• Tropical Pacific leads other regions.
• The role of ENSO residuals on decadal time scales?
![Page 5: Decadal variability in the Indo-Pacific ocean inferred from satellite data and ECCO assimilation Tong Lee NASA Jet Propulsion Laboratory, California Institute.](https://reader034.fdocuments.us/reader034/viewer/2022052608/5a4d1b877f8b9ab0599bd3f4/html5/thumbnails/5.jpg)
Schematics for zonally averaged view and horizontal view of time-mean Pacific & Indian-Ocean shallow MOCs
0N
Southeasterly trade wind Westerly
wind .
thermocline flow Cross-equatorial cell
10S20S
500 m
50 m
30S
Subtropical cell
Ekman flow
Indian OceanTrade wind
Ekman flow Ekman flow
Equatorward thermocline flow
Equatorward thermocline flow
N10S 10N
Pacific Ocean
Divergence of Ekman flow
Convergence of w. boundary & interior pycnocline flow
Ekman outflow
Pycnocline inflow
Bird’s eye view
![Page 6: Decadal variability in the Indo-Pacific ocean inferred from satellite data and ECCO assimilation Tong Lee NASA Jet Propulsion Laboratory, California Institute.](https://reader034.fdocuments.us/reader034/viewer/2022052608/5a4d1b877f8b9ab0599bd3f4/html5/thumbnails/6.jpg)
Implications of observed decadal wind & SSH to MOCsDecadal change of zonal wind ~ meridional Ekman flow (upper branch of MOC): reflect atmospheric bridge (anomalous Walker Circulation).
Decadal change of E-W SSH difference ~ thermocline flow (lower branch of MOC): reflect oceanic linkage (wave-transmission from NW Pacific to SE Indian Oceans)
Anomalous pycnocline flowAnomalous
pycnocline flow
Stronger tradewind
Anomalous Ekman
Anomalous Ekman
Weaker tradewind
Stronger tradewind
Weaker tradewind
![Page 7: Decadal variability in the Indo-Pacific ocean inferred from satellite data and ECCO assimilation Tong Lee NASA Jet Propulsion Laboratory, California Institute.](https://reader034.fdocuments.us/reader034/viewer/2022052608/5a4d1b877f8b9ab0599bd3f4/html5/thumbnails/7.jpg)
Volume (left) & temperature (right) fluxes of the Indonesian throughflow estimated by ECCO products
![Page 8: Decadal variability in the Indo-Pacific ocean inferred from satellite data and ECCO assimilation Tong Lee NASA Jet Propulsion Laboratory, California Institute.](https://reader034.fdocuments.us/reader034/viewer/2022052608/5a4d1b877f8b9ab0599bd3f4/html5/thumbnails/8.jpg)
Observed decadal change of Indian-Ocean trade wind & MOC strength estimated by ECCO assimilation
Trade wind
Estimated MOC
![Page 9: Decadal variability in the Indo-Pacific ocean inferred from satellite data and ECCO assimilation Tong Lee NASA Jet Propulsion Laboratory, California Institute.](https://reader034.fdocuments.us/reader034/viewer/2022052608/5a4d1b877f8b9ab0599bd3f4/html5/thumbnails/9.jpg)
Comparison of SSH trend for 1993-2000 (indicative of DecVar): large-scale similarity
Altimeter data
ECCO-JPL estimate
Used to estimate gyre circulation changes
![Page 10: Decadal variability in the Indo-Pacific ocean inferred from satellite data and ECCO assimilation Tong Lee NASA Jet Propulsion Laboratory, California Institute.](https://reader034.fdocuments.us/reader034/viewer/2022052608/5a4d1b877f8b9ab0599bd3f4/html5/thumbnails/10.jpg)
Weakening Western Subarctic Gyre
Strengthening Kuroshio recirculation gyre
Strengthening North Central Pacific Gyre
Strengthening South Pacific Subtropical Gyre
Mean
Decadal change
Barotropic streamfunction: mean (left) & decadal change (lower)
![Page 11: Decadal variability in the Indo-Pacific ocean inferred from satellite data and ECCO assimilation Tong Lee NASA Jet Propulsion Laboratory, California Institute.](https://reader034.fdocuments.us/reader034/viewer/2022052608/5a4d1b877f8b9ab0599bd3f4/html5/thumbnails/11.jpg)
Summary
• Near-coherent decadal tendency changes SSH & wind in the Indo-Pacific region at the end of the 20th century: broader than PDO.
• Equatorial Pacific SSH, forced by local trade wind, leads the changes.
• Anti-correlated changes of MOCs in the Pacific & Indian Oceans, thus opposite roles in regulating tropical heat content: atmospheric connection via Walker circulation & oceanic linkage by ITF.
• Coherent variations of subtropical & subpolar gyres: atmospheric tele-connections.
![Page 12: Decadal variability in the Indo-Pacific ocean inferred from satellite data and ECCO assimilation Tong Lee NASA Jet Propulsion Laboratory, California Institute.](https://reader034.fdocuments.us/reader034/viewer/2022052608/5a4d1b877f8b9ab0599bd3f4/html5/thumbnails/12.jpg)
PDO index
Nino3.4 index
Decadal signals from Reynolds SST
![Page 13: Decadal variability in the Indo-Pacific ocean inferred from satellite data and ECCO assimilation Tong Lee NASA Jet Propulsion Laboratory, California Institute.](https://reader034.fdocuments.us/reader034/viewer/2022052608/5a4d1b877f8b9ab0599bd3f4/html5/thumbnails/13.jpg)
SSH time series (black curves) in key regions further illustrate the tendency change around 2000
• Tropical Pacific leads other regions.
• The role of ENSO residuals on decadal time scales?
NINO3 3.4 index
PDO index