Complementarity of the Repeat Hydrography and Argo Programs by marcjackson

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									Complementarity of the Repeat Hydrography and Argo Programs
Gregory Johnson NOAA/Pacific Marine Environmental Laboratory

Sections

Floats

Complementarity

Temporal res.
Depth Horizontal res. Basin coverage

5-10 years
Full depth 0.5 degrees A few cuts

10 days
< 2000 dbar 3 degrees Full basin

Floats fill in for sections
Sections sample below floats Sections resolve eddies Floats fill in the interior

Boundary currents Velocity data
Calibrations Logistics

Resolved Density & ADCP
Pre, post, & in situ Primary ship user

Undersampled Dens. & 1000 m
Pre & historical Secondary user

Sections resolve boundaries Small x & t vs. large x & t.
Section data anchor floats Repeat Hydro deploys floats

Water-mass data Participants

Comprehensive Internatl’ climate

Temp. & salt Ditto

Opportunity for improvements Overlap in science interests

Floats:
(http://www.argo.ucsd.edu/)

•10-day intervals •3 degree spacing •Boundaries? •Covers all basins

Sections:
(http://www.clivar.org/carbon_hy dro/hydro_table.php)

•10-year intervals •0.5 degree spacing •Boundary currents •O(1) per basin

WOCE Section P16 (circa 1991)
(http://www-pord.ucsd.edu/whp_atlas/)

•Thisfor what of) what we get with Argo floats •But is (sort we get properties other than temperature, salinity (and velocity). . . water mass from a repeat section
–Full Waterto 2000 dbar (shallower for some locations) –Repeat Hydrography –Sampling column is nearly our only data source. –Resolves currents & better complement repeat hydro for other parameters? doesn’t blurred) –How might the Argo fronts from boundary to boundary & water mass boundaries are permit) –Lower spatial resolution than pictured (currents, fronts, (except when weather –Snapshot every decade but only .for a few longitudes (or latitudes) –But we get temporal information . .

Argo Deployments from Repeat Sections
January 27, 2005 at 46.5S, 150W aboard the R/V Revelle (CO2/CLIVAR line P16S)

Photo by Chris Sabine

Repeat Hydro Data Verify Argo Data
•Argo vs. P16S Repeat Hydro CTDs
–Blue hydro vs. red float –Usually co-located to 10 days and 50 km –Float goes only to 2000 dbar –Vertical spacing & finestructure? –Lateral Spacing & fronts?

•Zoom in on the mid-depth water
–12 floats deployed on P16S 2005
•Co-located 10 days and < 50 km •Float - Station S: 0.000  0.001

–10 floats deployed on P2 2004
•Float - Station S: -0.009  0.002

•Useful for climate research

Repeat Sections Quantify Water Masses
•South Pacific Eastern •WOCE P18 Section Data
–Along 103W in 1994 –Potential vorticity is low

•Subtropical Mode Water
–Hanawa & Talley (2001) –after Wong & Johnson (2003)

•Formed in High E-P region
–Winter evaporation & cooling –Warm salty over cold fresh –Turner angle is high –(Tu > 77 = density ratio < 1.6) –Potential for double diffusion

Argo Data Allow Temporal Analysis
•Seasonal Mode Water Ventilation •Float WMO 4900454
–Localized Near 20S, 112W

•Wintertime
–Latent cooling with . . . –Strong evaporation

•Low PV & Salty anomaly subducted

•Seasonal Anomaly Evolution
–High Spring Turner Angles –Favors Salt-fingering –Anomalies eroded –Migrate downward –after Johnson (2006)

•Interannual variations . . .

Argo Data Provide Large-Scale Context
•Willis et al. (2004)
–Theromosteric height anomalies to 750 m from situ temp profiles –SSH anomaly maps from satelllite altimeters –Correlate & map –Global, annual, mesoscale resolution

•Argo will allow expanded analysis
–Add halosteric component –2000 m depth
•Better correlations •Improved maps •Reduced errors
(Work with John Lyman & Josh Willis)

•Complementary to Repeat Hydrography
–Circulation shifts between occupations –Interior structure between sections –A16N repeats in 1993 vs. 2003 . . .

Perspective for A16N Repeat Differences
(40N to Iceland; after Johnson & Gruber, 2006)

SPWM
MOW

LSW

SPWM MOW LSW

Opportunity for Mutual Improvement?
(figures from Feely et al., 2005)

•Time Differences of AOU and DIC
–Big changes at SPMW base –Changes are well correlated

•Similar large AOU changes from decadal repeat sections in the:
–North Pacific –South Indian –Southern Ocean

•Repeat sections are sparse
–Only a few locations –Separated by decades

•Could floats help?

Maps of North Atlantic C* Distributions (C. Sabine)
Approach: • Make fits of C* to physical parameters from 2003 A16, A20, A22 repeat hydrographic sections (RMSE 5.6 µmol/kg, better than DIC RMSE of 11.4 µmol/kg)

• Apply fits to data from ARGO profiles from same year to map C* values across basin. • ARGO based C* distributions agree well with data along sections and maps are consistent with expected patterns. • Subtract WOCE maps from modern maps to determine anthropogenic accumulation.

Difficult to make good basin-scale maps of C* (or other parameters) from WOCE sections alone

Adding Oxygen Greatly Improves The Fit (C. Sabine)
Rmse = 11.4 µmol/kg without oxygen Rmse =3.7 µmol/kg with oxygen

Adding oxygen to ARGO floats globally will make these data much more relevant for biogeochemical studies.

Oxygen float project: Körtzinger, IFM-GEOMAR, Kiel/Germany
Oxygen (mmol m-3)
Pressure (dbar)

A

290 0

295

300

305

310

315

320

325

200

B

400

600

454

1600 Oxygen inventory Mixed layer depth

O2 m )

800

452 450 448 446 444 442 440 438 436 434

C

1400

Oxygen inventory (0-14000-1400 O m-2 ] 2 Oxygen inventory m) [mol m (mol

1000
1200 1000 800 600 400 200

Oct. 5, 2003 (profile 4) Oct. 26, 2003 (profile 7) Nov. 2, 2003 (profile 8) Dec. 7, 2003 (profile 13) Dec. 28, 2003 (profile 16) Feb. 8, 2004 (profile 22) Feb. 22, 2004 (profile 24) Mar. 21, 2004 (profile 28) Apr. 4, 2004 (profile 30) Apr. 11, 2004 (profile 31)

-2

1200

Mixed layer depth (m)

1400

1600

1800

432 0 250 270 290 310 330 350 5 25 45 65 85 470 490 510 530 550 250 270 290 310 330 350 370 390 410 430 450 105 125 145 165 185 2003

Julian day

2004

2000

Körtzinger et al. (2004). The ocean takes a deep breath. Science 306, 1337.

Also work by Riser, Freeland . . .

Conclusions
•Argo and Repeat Hydrography are highly complementary
•Sections:
•resolve boundary currents, fronts, eddies •sample to the bottom

•Floats:
•fill the interior between sections •fill in the years between repeat sections

•Adding oxygen to floats would increase usefulness for climate
•But there are jobs to do and funds to raise:
•Demonstrate sensor compatibility (need to show they won’t harm the floats)
•Provide and integrate well tested & calibrated hardware •Provide necessary increases in stored energy or float equivalents to offset energy use

•Finance increased telemetry costs
•Share in data management •Perform scientific quality control of data •Expectation of real-time data availability

Is it possible to use ARGO to estimate carbon changes?
Approach: Use MLR fits of shipboard data (A16N, A22, A20) to derive functions to estimate carbon from ARGO profiles.

Measured Parameters: T, S, P, Lat., Lon. http://www.argo.ucsd.edu/
2003 N. A. ARGO Profiles

Rmse = Measured Parameters: Temperature, Salinity, Pressure, Latitude, Longitude 5.6 µmol/kg 4.4 µmol/kg 11.4 Physical Parameters used in MLR Fits: Potential Temperature (θ), Salinity (S), Potential Density (σθ), Spiciness (π), Brunt-Vaisala frequency (N2)
Dissolved Inorganic Carbon Rmse = 11.4 µmol/kg

Examined Fits for a Variety of Carbon Parameters

Total Alkalinity Rmse = 4.4 µmol/kg

C* = DIC+0.688oxy0.5(Talk-0.094oxy) Rmse = 5.6 µmol/kg

C* = DIC+0.688oxy0.5(Talk-0.094oxy)

Another complication with C* approach is the assumption of constant Redfield ratios.

There appear to be large AOU changes on A16N that are of comparable magnitude to DIC changes.

∆AOU * 0.688 (µmol/kg)

Technology is ready and being implemented by a few investigators, but needs large-scale implementation to be most effective

Phase 2: Add pH to ARGO and use MLR fits of alk. to calculate full carbon system


								
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