Interannual Variability in the Extratropical Ocean Carbon System

Scott Doney (WHOI)

-Ubiquitous!!-Physical climate modes-Mechanisms & climate change-New approaches & experimental designs

Dore et al. (2002)

Hawaii Ocean Time-Series

Interannual Variability in Global Carbon Cycle

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

2

4

6

8

Global(NOAA)

Cape Grim(CSIRO)

0

30

Fossil Fuel

Pinatubo

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

-30

CO2 GROWTH RATE

El Nino

La Nina

Mauna Loa(Scripps/NOAA)

(R J Francey, pers. Com)

Atmospheric CO2 growth rate

El Niño : 0.2-0.4 PgC/yNon El Niño : 0.7-0.9 PgC/yAverage: 0.6±0.2 PgC/y

-Dense time/space coverage-Agreement among field data, ocean models & “top-down” atmospheric estimates

Feely et al. (2003)

Equatorial Pacific

Bousquet et al. (2000)

ocean modelatmosphere

data

Le Quere et al. (2000)(also Obata et al. 2003)

1997-2002

Natural Climate Modes

NAO

NAO: North Atlantic OscillationPDO: Pacific Decadal OscillationAAO: 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

Wang and Schimel (2003)

Surface Pressure Anomaly

Regional Spatial Patterns

Wang and Schimel (2003)

-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

Correlation-0.6 +0.8

NAO Index

20001950 20501900

obs.models

SubtropicalNorth Atlantic

Gruber et al. (2002)

Negative NAO => +WML -SST +entrainment +production +CO2 uptake

Extrapolate to subtropical gyre =>±0.2 PgC/y

whole basin =>±0.3 PgC/y

Mixed Layer

Entrainment

CO2 uptake

Production

Transport

PDO

Pacific Decadal Oscillation ML Anomaly

Wang & Schimel (2003)

Karl et al. (2001)

DepthIntegrated Chlorophyll

Hare & Mantura (2000)

++

Subtropicalnutrient limited prod.+ML => +Chlorophyll + ProductionSubpolar/Polarlight limited prod.-ML => +Productionmultiple impacts on higher trophic levels (e.g. zooplankton, fisheries, mammels)

Climate Change Response

-Regional climate change signals-Surface warming, high latitude freshening, increased stratification, reduced mixed layer depths & sea-ice -Productivity lower in subtropics, higher in subpolar

productivity

Sarmiento et al. (submitted)

Multi-Century Coupled Carbon/Climate Simulations

Net CO2 Flux (Pg C/yr)-1.5

+1.5

-Fully prognostic land/ocn BGC and carbon/radiation-“Stable” carbon cycle and climate over 200y-Projection of climate change on natural modes-Detection & attribution

Surface Temp.13.6

14.1

Fung, Doney, Lindsay & John2000 year

Variability Mechanisms Particle

exportAir-seaflux

1

.3

10

3

.1 Fresh-water

mol C/m^2

Fung, Doney, Lindsay & John

-Regions of high variability in North Atlantic & Pacific, tropics and Southern Ocean-Mechanisms differ across regions

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

Mahowald et al. (2003)

(standard deviation/mean)

Ironflux

Air-seaCO2 flux

Zonal Anomalies

N2 Fixation

Doney, Dusenberry, Moore & Mahowald

SeaWiFS Ocean Color Data (1997-2003)

April 2000Oct. 1998

Coherent Regional-Scale Patterns

SeaWiFS Monthly Anomaly SeaWiFS Monthly Anomaly

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

time

space

Local GlobeOceanBasin

Regional(500 km)

Centuries

Decadal

Inter-annual

Seasonal

DailyRemotesensing

Hourly

Process Studies

Repeat Sections

Surface transectsFloats/driftersOcean Observatories

ShipTime-Series

MooredTime-Series

Atm. CO2

O2/N2

New Technology & Observational Paradigms

Conclusions

AcknowledgementsJ. Dusenberry & S. McCue WHOI K. Lindsay NCARNSF and NSF/ONR NOPPCCSM & the NCAR CSL

-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

LeQuere et al. (2000)

Obata et al. (2003)

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

Bousquet et al. (2003)

Regional Spatial Patterns

Wang and Schimel (2003)

-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

Correlation Correlation-0.6 +0.8 +0.8-0.6

Monthly SeaWiFS Ocean Color Anomalies

standard deviation

standard deviation/mean

-DIC supply (dominant) & export out of phase-General agreement among field data, ocean models & “top-down” atmospheric estimates-But what about the extratropics?

Obata et al. (2003)

Obata et al. (2003)

physicsexport air-sea

flux

Equatorial Pacific

Bousquet et al. (2000)

ocean modelatmosphere

data

Le Quere et al. (2000)

Antarctic Circumpolar Wave

Le Quere et al. (2002)

+0.1

-0.1

Wind Stress& CO2 fluxAnomalies

Obata et al. (2003)

-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

Global Carbon Cycle

Doney and Schimel (2001)

-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

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.

Greene et al. 2003 Chavez et al. 2003

-Impacts on both biomass and species competition-Multi-decadal “regime shifts” integrating higher frequency climate variability

Community Structure & Higher Tropic Levels

Climate Modes & Change Change

SeaWiFS Ocean Color Data (1997-2003)