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A 26 o N update and U.S. AMOC Effort clivar

A 26 o N update and U.S. AMOC Effort www.clivar.us.org. A new interagency program with a focus on AMOC monitoring and prediction capability Presented at the Office of Climate Observations Annual Meeting on September 3, 2008 on behalf of the U.S.AMOC Science Team by Molly Baringer.

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A 26 o N update and U.S. AMOC Effort clivar

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  1. A 26oN update and U.S. AMOC Effort www.clivar.us.org A new interagency program with a focus on AMOC monitoring and prediction capability Presented at the Office of Climate Observations Annual Meeting on September 3, 2008 on behalf of the U.S.AMOC Science Team by Molly Baringer NASA Earth Science Division Satellite data analyses, modeling and space-based observations NOAA Climate Program Office Observing systems, monitoring, climate modeling NSF Geosciences program Process studies, models, and observations

  2. The National Ocean Research Priorities Plan and Implementation Strategy presents research priorities that focus on the most compelling issues in key areas of interaction between society and the ocean.

  3. Unanswered questions surrounding the AMOC include: • What is the current state of the AMOC? • How has the AMOC varied in the past on interannual to centennial time scales? • What governs AMOC changes? • Is the AMOC predictable on 10-100 year timescales? • What are the impacts of AMOC variability and change? October 2007: Implementation Strategy for a JSOST Near-Term Priority: Assessing Meridional Overturning Circulation Variability: Implication for Rapid Climate Change

  4. Western Boundary Time Series (WBTS) U.S. PI’s: M. O. Baringer1, C. S. Meinen1, S. L. Garzoli1 1 NOAA-Atlantic Oceanographic and Meteorological Laboratory U.S. Collaborators: B. Johns2, L. Beal2 (MOCHA/NSF) 2 RSMAS, University of Miami, Miami FL International Collaborators: H. Bryden3, S. Cunningham3, T. Kanzow3, J. Marotzke4, J. Hirschi3 (RAPID/NERC) 3 National Oceanography Centre, Southampton, U.K. 4 Max Planck Institut, Hamburg, Germany

  5. An Observing System for Meridional Heat Transport Variability in the Subtropical Atlantic Funding Agency: NSF (Funded period 2004 – 2014) U.S. PI’s: B. Johns1, M. Baringer2, L. Beal1, C. Meinen2 1 RSMAS, University of Miami, Miami FL 2 NOAA/AOML, Miami, FL International Collaborators’s: H. Bryden3, S. Cunningham3, T. Kanzow3, J. Marotzke4 (RAPID/NERC) 3 National Oceanography Centre, Southampton, U.K. 4 Max Planck Institut, Hamburg, Germany U.S. Collaborators: S. Garzoli2 (WBTS/NOAA) Goal:“To set in place a system for continuous observation of the meridional overturning circulation and northward heat transport in the Atlantic Ocean, with which to document its variability and its relationship to observed climate fluctuations, and to assess climate model predictions.” Specific Objectives: • Determine the “present day” mean MOC & MHT at 26°N and year-to-year variability • Determine the spectrum of MOC variability, and related mechanisms, to help optimize MOC observing systems • Provide a benchmark of MOC strength and variability for climate and ocean synthesis models Louise Bell / Neil White, CSIRO

  6. Driving Florida current Variability with wind stress curl (WSC) variations DiNezio et al, 2008, JPO, in press. Meinen et al, 2008, JGR, in press Correlation between WSC and the NAO

  7. Influence of the RAPID-MOC and Gulf Stream cable measurements on the ECCO-GODAE global state estimate J. Baehr, 2008, JPO, submitted

  8. Vertical structure of the Florida Current 87% Variance explained by the first EOF mode Using more than 100 insitu sections across the Florida Current to develop a technique to estimate the vertical structure of the current given only the total transport.

  9. Heat Transport Meridional Heat Transport: Qnet=∫∫ρcp vθ dx dz Qnet = QFC + QEK + QWB + QINT QFC→ Cable voltage calibrated for temperature transport, (Shoosmith et al., 2005) r = 0.94, σ = 0.1 PW QEK→ QuickScat wind stress (daily) • Reynolds SST (weekly) QWB→ Directly calculated from moored CM’s/thermistors in Abaco WB array QINT→ Zonally-averaged interior transport profile from endpoint geostrophic moorings • Seasonally-averaged interior hyrdographic climatology (Hydrobase, R. Curry) Missing: Contribution to QINT by spatially correlated v,T variability across interior: “Gyre/eddy” heat transport = ∫∫ ρcp v'θ' dx dz

  10. Annual Mean Heat Transport Quantity Mean Value Std. error Bias error Qarray 1.26* ± 0.06 ± 0.08 (?) Qgyre/eddy 0.10 ± 0.03 - __________ ______________ _____________ 1.36 ± 0.07 ± 0.08 * deseasonalized → Qnet = 1.36 ± 0.11 PW RAPID/MOCHA XBT estimates

  11. Part One Conclusions • Annual mean (2004-2006) MHT across 26°N = 1.36 ± 0.11 PW. Consistent with previous direct estimates (within errors), but at upper end. • Annual mean MOC transport = 18.8 ± 5 Sv is also slightly larger than estimates from WOCE period (16-18 Sv). • Short term MHT variability is large. Range -> 0.1 – 2.5 PW, Std. Dev = 0.41 PW and. About half is due to Ekman transport variability, remainder due to geostrophic variability. Range of variability is consistent with eddy-permitting/eddy-resolving models, but geostrophic variability may play a bigger role than previously suggested by models (→ Hirschi et al., 2007) • Seasonal cycle emerging… in agreement w/ prior climatological estimates and model results. MOC dominated by FC and interior ocean while the MHT dominated by Ekman annual cycle. • Mean Volume and MHT estimates from the RAPID-MOC array should provide one of the best constrained benchmarks for indirect estimates of the ocean transports (from flux climatologies, TOA radiation, etc.), and for comparison with numerical models.

  12. U.S. AMOC Scientific Objectives • The design and implementation of an AMOC monitoring system • An assessment of AMOC’s role in the global climate • An assessment of AMOC predictability Recommended Activities • Develop an AMOC state estimate or “fingerprint” • Monitor AMOC transports • Evaluate coherence and connectivity of AMOC circulation and transports • Assess AMOC observing systems with ocean models • Reconstruct AMOC variability and associated property fields • Model the ocean state during the instrumental period • Develop longer-term proxies for AMOC variability • Diagnose mechanisms of AMOC variability and change • Assess AMOC predictability • Determine impact and feedback of AMOC variability • Assess role of AMOC in producing observed changes

  13. Evaluation of Meridional Transport of Water and Heat in the Atlantic Ocean Using Satellite Data PI: W. Timothy Liu, Co-I: XiaosuXie 1 Jet Propulsion Laboratory, NASA, Pasadena, California Comparing annual mean Atlantic meridional heat transport. Red curve is calculated from four components of satellite surface heat flux. The green curve is computed from ECCO data. Various symbols are from past studies, from surface heat flux or hydrographic data.

  14. Line W: A sustained measurement program sampling the North Atlantic Deep Western Boundary Current and Gulf Stream at 39°N U.S. PI’s: J. Toole1, R. Curry1, T. Joyce1, M. McCartney1 and W. Smethie, Jr.2 1 Woods Hole Oceanographic Institution, Woods Hole, MA 02543 2 Lamont Doherty Earth Observatory, Palisades, NY 10964 International PI’s: J. Smith3 3 Bedford Institute of Oceanography, Dartmouth, Nova Scotia B2Y 4T3 Canada Line W: Volume transport time series

  15. Export Pathways from the Subpolar North Atlantic Funding Agency: NSF (2007 – 2008) PI’s: Amy Bower1 and Susan Lozier2 1 Dept. of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA 2 Earth and Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, NC Goal:To obtain a better understanding and description of the pathways of waters that constitute the lower limb of the Atlantic Meridional Overturning Circulation, with a focus on the Labrador Sea Waters Specific Objectives: • Conduct a field program with RAFOS floats seeded in the Labrador Sea to directly assess pathways • Conduct data and modeling studies to assess dynamics controlling these pathways and their temporal variability

  16. Pathways of meridional circulation in the North Atlantic Ocean U.S. PI’s: P.B. Rhines1, S. Hakkinen2 1 Dept of Oceanography, U. Washington, Seattle, WA 2 NASA Goddard Space Flight Center, Greenbelt, MD Surface drifter tracks show significant changes since year 2000 in the path of the surface currents associated with the North Atlantic Current. Surface drifter tracks entering (cyan) and leaving (magenta) the region (30-50W, 35-45N): during 1991-2000, top, and during 2001-2006, bottom.

  17. LC NAC subtropical strong NAC weak subtropical Assessing Meridional Transports in the North Atlantic Ocean U.S. PI’s: K. A. Kelly1, L. Thompson 1 Applied Physics Lab, University of Washington , Seattle, WA 2 School of Oceanography, U. Washington, Seattle, WA 15 years of surface currents shows that the North Atlantic Current is stronger when the subtropical gyre is weaker (and vice-versa)

  18. Decadal Climate Predictability and Predictions – Focus on the Atlantic U.S. PI’s: T.L. Delworth, A.J. Rosati Geophysical Fluid Dynamics Laboratory/NOAA Princeton, NJ, USA Goal: Determine role of AMOC in producing observed climatic variability Difference in simulated summer rainfall when the AMOC is weak (cold North Atlantic) versus when it is strong (warm North Atlantic). Units are cm per day. Blue indicates less rain when AMOC is weak. Results from GFDL CM2.1 model.

  19. Towards An Understanding Of The Role of The Atlantic Thermohaline and Wind-Driven Circulation In Tropical Atlantic Variability (TAV) U.S. PI’s: P. Chang1, R. Saravanan2 and R. Zhang3 Dept of Oceanography, Texas A&M University, College Station, TX Dept of Atmospheric Sciences, Texas A&M University, College Station, TX Geophysical Fluid Dynamics Laboratory, Princeton, NJ Fig. 1: Equatorial Atlantic ocean temperature change in response to North Atlantic fresh water input in GFDL CM2.1. Fig. 2: Simulated changes in monsoon rainfall over West Africa. (After Chang et al. 2008)

  20. Recommended Activities • Develop an AMOC state estimate or “fingerprint” • Monitor AMOC transports • Evaluate coherence and connectivity of AMOC circulation and transports • Assess AMOC observing systems with ocean models • Reconstruct AMOC variability and associated property fields • Model the ocean state during the instrumental period • Develop longer-term proxies for AMOC variability • Diagnose mechanisms of AMOC variability and change • Assess AMOC predictability • Determine impact and feedback of AMOC variability • Assess role of AMOC in producing observed changes New U.S. AMOC Projects starting soon: • Variability and Forcing Mechanisms of the Atlantic Meridional Overturning Circulation - Tong Lee/ Jet Propulsion Laboratory with Harvard University, University of Hamburg, and Laboratoire de Physique des Oceans • Atlantic MOC Observing System Studies Using Adjoint Models - Carl Wunsch/ MIT with AER, Inc. • A NOPP Partnership for AMOC: Focused Analysis of Satellite Data Sets - Peter Minnett/ Miami with Remote Sensing Systems, Inc. • Observing System Simulation Experiments for the Atlantic Meridional Overturning Circulation - George Halliwell/Miami with NOAA AOML

  21. Summary • U.S. effort is spinning up; some early tangible results • Continued partnership with international collaborators is essential to the community-wide goals of AMOC monitoring and prediction • Particular need for collaboration is for transatlantic measurements; the monitoring of subpolar North Atlantic and subtropical South Atlantic are key priorities.

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