Interannual Variability in the Extratropical Ocean Carbon System Scott Doney (WHOI) -Ubiquitous!! -Physical climate modes -Mechanisms & climate change -New approaches & experimental designs Hawaii Ocean Time-Series Dore et al. (2002)

Interannual Variability in Global Carbon Cycle Atmospheric CO2 growth rate Francey -Ocean sequesters ~30% of fossil fuel CO2 -Variability dominated by land sinks but role for the oceans -Primary global signal associated with ENSO events

Equatorial Pacific El Niño : 0.2-0.4 PgC/y Non El Niño : 0.7-0.9 PgC/y Average: 0.6±0.2 PgC/y -Dense time/space coverage -Agreement among field data, ocean models & “top-down” atmospheric estimates ocean model atmosphere data Bousquet et al. (2000) Le Quere et al. (2000) (also Obata et al. 2003) 1997-2002 Feely et al. (2003)

Natural Climate Modes NAO: North Atlantic Oscillation Surface Pressure Anomaly NAO: North Atlantic Oscillation PDO: Pacific Decadal Oscillation AAO: Antarctic Oscillation -Shift of mass from subpolar lows and subtropical highs -Changes in winds, SST, ocean convection, freshwater flux, … -”Intrinsic” atmospheric variability (ocean, stratosphere) -Tropical-extratropical interactions NAO Wang and Schimel (2003)

Regional Spatial Patterns -Modes expressed on regional (sub-basin) scales with significant cancellation (dipole pattern) -Historical and future climate change appear to project onto natural modes -Spatial patterns may evolve with time Wang and Schimel (2003) -0.6 Correlation +0.8 models NAO Index obs. 1900 1950 2000 2050

Subtropical North Atlantic Mixed Layer Negative NAO => +WML -SST +entrainment +production +CO2 uptake Extrapolate to subtropical gyre => ±0.2 PgC/y whole basin => ±0.3 PgC/y CO2 uptake Entrainment Transport Production Gruber et al. (2002)

Pacific Decadal Oscillation ML Anomaly Wang & Schimel (2003) + + PDO Depth Integrated Chlorophyll Subtropical nutrient limited prod. +ML => +Chlorophyll + Production Subpolar/Polar light limited prod. -ML => +Production multiple impacts on higher trophic levels (e.g. zooplankton, fisheries, mammels) Karl et al. (2001) Hare & Mantura (2000)

Climate Change Response productivity Sarmiento et al. (submitted) -Regional climate change signals -Surface warming, high latitude freshening, increased stratification, reduced mixed layer depths & sea-ice -Productivity lower in subtropics, higher in subpolar

Multi-Century Coupled Carbon/Climate Simulations +1.5 14.1 -1.5 13.6 Surface Temp. Net CO2 Flux (Pg C/yr) year 200 Fung, Doney, Lindsay & John -Fully prognostic land/ocn BGC and carbon/radiation -“Stable” carbon cycle and climate over 200y -Projection of climate change on natural modes -Detection & attribution

Variability Mechanisms Particle export Air-sea flux 1 .3 10 3 .1 Fresh- water mol C/m^2 -Regions of high variability in North Atlantic & Pacific, tropics and Southern Ocean -Mechanisms differ across regions Fung, Doney, Lindsay & John

Atmospheric Dust Deposition -Significant interannual variability, particularly in the North Atlantic -Driven mostly by atmospheric transport, not sources -Largest fraction is synoptic, within month variability (standard deviation/mean) Mahowald et al. (2003)

Iron flux Zonal Anomalies Air-sea CO2 flux N2 Fixation Doney, Dusenberry, Moore & Mahowald

SeaWiFS Ocean Color Data (1997-2003)

Coherent Regional-Scale Patterns SeaWiFS Monthly Anomaly SeaWiFS Monthly Anomaly Oct. 1998 April 2000

Antarctic Circumpolar Wave Le Quere et al. (2002) -Positive/negative physical anomalies propagate around southern ocean with 8-10 year time-scale -Ocean color variability appears coherent across basin -Differential regional biological responses to mixed layer depth changes depending on light versus nutrient limitation

New Technology & Observational Paradigms time space Local Globe Ocean Basin Regional (500 km) Centuries Decadal Inter-annual Seasonal Daily Remote sensing Hourly Process Studies Repeat Sections Surface transects Floats/drifters Ocean Observatories Ship Time-Series Moored Atm. CO2O2/N2 New Technology & Observational Paradigms

Conclusions -Common feature of almost all ocean time-series -Regional time-space structured by climate modes & biology -Natural experiments for studying climate change response -Require more spatially “extensive” design for ocean observation Acknowledgements J. Dusenberry & S. McCue WHOI K. Lindsay NCAR NSF and NSF/ONR NOPP CCSM & the NCAR CSL

Global & Extratropical Variability LeQuere: ±0.4 (70% Eq. Pac.) Obata: ±0.23 (>50% Eq. Pac. ~30% Southern) -Only partial reconciliation with atmosphere inversions -Poor data coverage outside of equatorial Pacific LeQuere et al. (2000) Obata et al. (2003) Bousquet et al. (2003)

Regional Spatial Patterns Wang and Schimel (2003) -0.6 Correlation +0.8 -0.6 Correlation +0.8 -Modes expressed on regional (sub-basin) scales with significant cancellation (dipole pattern) -Historical and future climate change appear to project onto natural modes -Spatial patterns may evolve with time

Monthly SeaWiFS Ocean Color Anomalies standard deviation standard deviation/mean

Equatorial Pacific -DIC supply (dominant) & export out of phase physics -DIC supply (dominant) & export out of phase -General agreement among field data, ocean models & “top-down” atmospheric estimates -But what about the extratropics? export air-sea flux Obata et al. (2003) Bousquet et al. (2000) ocean model atmosphere data Le Quere et al. (2000) Obata et al. (2003)

Antarctic Circumpolar Wave -Ocean response to annular mode in the atmosphere -Different regional biological responses to mixed layer depth changes -Air-sea CO2 flux correlated with wind stress/speed Le Quere et al. (2002) Wind Stress & CO2 flux Anomalies +0.1 -0.1 Obata et al. (2003)

Global Carbon Cycle -Ocean sequester ~30% of fossil fuel CO2 -Human perturbations overlay large natural background C cycle -Climate responses and feedbacks of ocean C sink not well known Human perturbations due to fossil fuel combustion and land-use change occur on top of a large natural background cycle coupling the land, atmosphere, and ocean -Ocean now sequestering ~30% of fossil fuel CO2 -Human perturbations overlay large natural background C cycle -Climate responses and feedbacks of ocean C sink not well known -Quantitative understanding needed of mechanisms controlling biological productivity Doney and Schimel (2001)

Physical & Biological Controls pCO2 = f(Temp., Salinity, DIC, Alkalinity) + (+) + - Net Community Prod. Winter mixed layer Circulation Light Nutrient/ DIC Supply Export Winds, Heat & Freshwater Fluxes Dust/iron CO2 O2 Remineralization Regenerated Prod.

Community Structure & Higher Tropic Levels -Impacts on both biomass and species competition -Multi-decadal “regime shifts” integrating higher frequency climate variability Time series of C. finmarchicus abundance from (a) the North Sea and (b) the Gulf of Maine/Scotian Shelf region. Time series are based on Continuous Plankton Recorder (CPR) data collected for C. finmarchicus from the North Sea since the late 1940s and from the Gulf of Maine/Scotian Shelf region since the late 1950s. Data from the Gulf of Maine are indicated by circles and from the Scotian Shelf by triangles. Methods of sample collection and processing have been described by Hardy (1939); Colebrook (1975), and Jossi and Goulet (1993). (c) Time series of the NAO index from 1955 to 1999. The NAO index is the mean difference, expressed as an anomaly from the long-term mean, in atmospheric pressure during winter between the subtropical high pressure system of the North Atlantic, measured in Lisbon, Portugal, and the subpolar low pressure system, measured in Stykkisholmur, Iceland (Hurrell, 1995). (d) Cross-correlation analyses between C. finmarchicus abundance and the NAO index. Results of the analyses of data from the North Sea are indicated by rectangles and from the Gulf of Maine during 1961–1989 and 1961–1999, respectively by triangles and circles. (e) Regression between C. finmarchicus abundance in the North Sea and the NAO index with no time lag. (f) Regression between C. finmarchicus abundance in the Gulf of Maine and the NAO index with a time lag of 4 years, 1961–1989 (dashed) and 1961–1999 (continuous). Greene et al. 2003 Chavez et al. 2003

Climate Modes & Change Change

SeaWiFS Ocean Color Data (1997-2003)