A 26oN update and U.S. AMOC Effort www.clivar.us.orgA new interagency program with a focus on AMOC monitoring

and prediction capability Present by Molly Baringer

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

NSF Geosciences programProcess studies, models, and observations

NOAA Climate Program Office Observing systems, monitoring, climate modeling

NASA Earth Science DivisionSatellite data analyses, modeling and space-based observations

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.

• 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?

Unanswered questions surrounding the AMOC include:

October 2007: Implementation Strategy for a JSOST Near-Term Priority: Assessing Meridional Overturning Circulation Variability: Implication for Rapid Climate Change

Western Boundary Time Series (WBTS)Western Boundary Time Series (WBTS)U.S. PI’s: M. O. BaringerU.S. PI’s: M. O. Baringer11, C. S. Meinen, C. S. Meinen11, S. L. Garzoli, S. L. Garzoli11 1 1 NOAA-Atlantic Oceanographic and Meteorological Laboratory

U.S. Collaborators: B. JohnsU.S. Collaborators: B. Johns22, L. Beal, L. Beal2 2 (MOCHA/NSF)(MOCHA/NSF) 2 2 RSMAS, University of Miami, Miami FL

International Collaborators: H. BrydenInternational Collaborators: H. Bryden33, S. Cunningham, S. Cunningham33, , T. KanzowT. Kanzow33, J. Marotzke, J. Marotzke4, 4, J. HirschiJ. Hirschi33 (RAPID/NERC) (RAPID/NERC) 3 National Oceanography Centre, Southampton, U.K. 4 Max Planck Institut, Hamburg, Germany

Goal:To provide time series observations of the two main components of the meridional overturning circulation in the Subtropical North Atlantic.

An Observing System for Meridional Heat Transport Variability An Observing System for Meridional Heat Transport Variability in the Subtropical Atlanticin the Subtropical Atlantic

Funding AgencyFunding Agency: NSF (Funded period 2004 – 2014): NSF (Funded period 2004 – 2014) U.S. PI’s: B. JohnsU.S. PI’s: B. Johns11, M. Baringer, M. Baringer22, L. Beal, L. Beal11, C. Meinen, C. Meinen22

1 RSMAS, University of Miami, Miami FL 2 NOAA/AOML, Miami, FL

International Collaborators’s: H. BrydenInternational Collaborators’s: H. Bryden33, S. Cunningham, S. Cunningham33, T. Kanzow, T. Kanzow33, J. Marotzke, J. Marotzke44 (RAPID/NERC) 3 National Oceanography Centre, Southampton, U.K. 4 Max Planck Institut, Hamburg, Germany

U.S. Collaborators: S. GarzoliU.S. Collaborators: S. Garzoli22 (WBTS/NOAA) (WBTS/NOAA)

GoalGoal:: “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

The RAPID-MOC 26.5°N Array

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WESTEASTINT )]()([)/()(0

Basin wide integratedinternal transports (TINT) from zonal density gradient

Transport through western boundary wedge (TWBW) from current meter measurements

Cunningham et al. (2007) Kanzow et al. (2007) Johns et al. (2008)

→ Funded through 2014 - will provide a 10 year time series

(2004-2014)

Driving Florida current Variability

with wind stress curl (WSC) variationsDiNezio et al, 2008, JPO, in press.Meinen et al, 2008, JGR, in press

Correlation between WSC and the NAO

Gulf Stream Transport through the Straits of Florida:Transport profiles

Transports [Sv]are projected on empirical verticalmode

Gulf Stream transport across 27N

[Sv/m]

Transport perunit of depthprofiles [Sv/m]

Part One Conclusions• Annual mean MOC transport = 18.8 ± 5 Sv is also slightly larger than estimates from WOCE period (16-18 Sv).

•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.

•Annual mean (2004-2006) MHT across 26°N = 1.36 ± 0.11 PW. Consistent with previous direct estimates (within errors), but at upper end.

• 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)

• The design and implementation of an AMOC monitoring system• An assessment of AMOC’s role in the global climate • An assessment of AMOC predictability

U.S. AMOC Scientific Objectives

• 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

Recommended Activities

U.S. PI’s: J. TooleU.S. PI’s: J. Toole11, R. Curry, R. Curry11, T. Joyce, T. Joyce11, M. McCartney, M. McCartney11 and W. Smethie, Jr. and W. Smethie, Jr.22

1 Woods Hole Oceanographic Institution, Woods Hole, MA 02543 1 Woods Hole Oceanographic Institution, Woods Hole, MA 02543

2 Lamont Doherty Earth Observatory, Palisades, NY 10964

International PI’s: J. SmithInternational PI’s: J. Smith3 3 3 Bedford Institute of Oceanography, Dartmouth, Nova Scotia B2Y 4T3 Canada

Line W: Volume transport time seriesLine W: Volume transport time series

Line W: A sustained measurement program sampling the North Line W: A sustained measurement program sampling the North Atlantic Deep Western Boundary Current and Gulf Stream at 39Atlantic Deep Western Boundary Current and Gulf Stream at 39°°NN

Export Pathways from the Export Pathways from the Subpolar North AtlanticSubpolar North AtlanticFunding AgencyFunding Agency: NSF (2007 – 2008): NSF (2007 – 2008)

PI’s: Amy BowerPI’s: Amy Bower11 and Susan Lozier and Susan Lozier22

1 Dept. of 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

GoalGoal:: 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

Pathways of meridional circulation in the North Atlantic Ocean U.S. PI’s: P.B. RhinesU.S. PI’s: P.B. Rhines11, S. Hakkinen, S. Hakkinen22

1 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 currentsassociated 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.

15 years of surface currents shows that the

North Atlantic Current is stronger when the

subtropical gyre is weaker (and vice-versa)

strong NAC

weak subtropical

NACLC

subtropical

Assessing Meridional Transports in the North Assessing Meridional Transports in the North Atlantic OceanAtlantic OceanU.S. PI’s: K. A. KellyU.S. PI’s: K. A. Kelly11, L. Thompson, L. Thompson

1 1 Applied Physics Lab, University of Washington , Seattle, WA 2 School of Oceanography, U. Washington, Seattle, WA

Evaluation of Meridional Transport of Water and Heat in the Atlantic Ocean Using Satellite Data PI: W. Timothy Liu, Co-I: Xiaosu XiePI: W. Timothy Liu, Co-I: Xiaosu Xie

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.

1 1 Jet Propulsion Laboratory, NASA, Pasadena, California

Decadal Climate Predictability and Predictions – Decadal Climate Predictability and Predictions – Focus on the AtlanticFocus on the AtlanticU.S. PI’s: T.L. Delworth, A.J. RosatiU.S. PI’s: T.L. Delworth, A.J. Rosati

Geophysical Fluid Dynamics Laboratory/NOAA Princeton, NJ, USAGeophysical Fluid Dynamics Laboratory/NOAA Princeton, NJ, USA

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.

Goal: Determine role of AMOC in producing observed climatic variability

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)

U.S. PI’s: P. ChangU.S. PI’s: P. Chang11, R. Saravanan, R. Saravanan22 and R. Zhang and R. Zhang33

1Dept of Oceanography, Texas A&M University, College Station, TX

2Dept of Atmospheric Sciences, Texas A&M University, College Station, TX

3Geophysical Fluid Dynamics Laboratory, Princeton, NJ

Towards An Understanding Of The Role of The Atlantic Thermohaline and Wind-Driven Circulation In Tropical Atlantic Variability (TAV)

• 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

• 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

New U.S. AMOC Projects starting soon:

Recommended Activities

• 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?

1. What is the optimal observing system design for the AMOC? How could the system components be prioritized and phased to accommodate funding constraints?

2. Is there an identifiable and measurable AMOC fingerprint that can be used to constrain the requirements for an AMOC observing system?

3. What aspects or regions of the circulation are likely to require more intensive measurements, based on existing observations?

4. How should critical societal impacts of AMOC guide observing system

design and phasing?

Outcomes

AMOC Open Science MeetingMay 4-6 2009, Annapolis, MD

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.