A Decline in the Northern A Decline in the Northern Hemisphere COHemisphere CO22 Sink Sink

from 1992 - 2003from 1992 - 2003

John MillerJohn Miller11, Pieter Tans, Pieter Tans11, Jim , Jim WhiteWhite22, Ken Masarie, Ken Masarie11, Tom , Tom

ConwayConway11, Bruce Vaughn, Bruce Vaughn22, Jim , Jim RandersonRanderson33, Neil Suits, Neil Suits44

1. NOAA/CMDL, Boulder2. INSTAAR, University of Colorado, Boulder3. U. of California, Irvine4. Colorado State University, Fort Collins

OutlineOutline

1.1. Trends in NH COTrends in NH CO22 data indicate a data indicate a change in the sink.change in the sink.

2.2. Two reasons why change originates Two reasons why change originates in the terrestrial biosphere.in the terrestrial biosphere.

3.3. What might be causing the change?What might be causing the change?

Conceptual ModelConceptual Model

FF

Rectifier Sink

COCO22 = CO = CO22 Site – CO Site – CO22 SPO = SPO =Fossil Fuel + Sink (+ rectifier)Fossil Fuel + Sink (+ rectifier)

Meridional COMeridional CO22 Gradient Gradient

19981992

2003

Gradient increasing; big jump from 1998-2003

MBLContinentalHi-Altitude

Fits to MBL

Sites used in studySites used in study

Determining trends at a siteDetermining trends at a site

SPO

ICE

CO

2 (p

pm

)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

bal

tap

uum

bme

bmw

gmi

key

kum

mhd mid

shm al

t

brw

ice

stm

zep

Site Code

Sit

e-S

PO

tre

nd

(p

pm

/yr)

Boreal marineTemperate marineContinental

Distribution of Trends: 1992-2003Distribution of Trends: 1992-2003

Expected trend from FF

•14/16 sites increase faster than expected: p < 0.01•Excluding 1992 and/or 2003 p < 0.05

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

ask ba

lb

sch

un

kzd

kzm lef

tap

uta

uu

mw

isw

lga

zrb

me

bm

wg

mi

key

kum

mh

dm

idsh

m alt

brw ice

stm

zep

Site code

Sit

e-S

PO

tre

nd

(p

pm

/yr)

Boreal marineTemperate marineContinental

Distribution of Trends: 1997-2003Distribution of Trends: 1997-2003

Expected trend from FF

Continental – Marine trend differences indicate a terrestrial origin.

Could continental Could continental trendtrend signal be Fossil? signal be Fossil?

-5

-4

-3

-2

-1

0

1

2

3

ask bal bsc hun kzd kzm lef tap uta uum wis wlg

site code

sit

e-M

BL

tre

nd

[p

pb

CO

/yr]

1.7 ppb/yr

MBL

Site

•Given a CO/CO2 emissions ratio of 10 ppb/ppm max. fossil fuel contribution of 0.2 ppm/yr.

What about changes in N/S transport ? What about changes in N/S transport ?

North/South SFNorth/South SF66 differences from 1997-2003 differences from 1997-2003 indicate a trend in inter-hemispheric exchange.indicate a trend in inter-hemispheric exchange.

Decreasing IHE implies less fossil emissions Decreasing IHE implies less fossil emissions stored in the NH.stored in the NH.

Thus, even larger sink changes are required to Thus, even larger sink changes are required to explain the observed gradient, 1997-2003.explain the observed gradient, 1997-2003.

11.1

1.21.3

1.41.5

1.61.7

1996 1998 2000 2002 2004

Inte

r-h

emis

ph

eric

exc

han

ge

tim

e [y

r]

Use 2D model to quantify sink Use 2D model to quantify sink changes.changes.

1.1. A 2D model of atmospheric transport to A 2D model of atmospheric transport to quantify the flux changes, andquantify the flux changes, and

2.2. Measurements of Measurements of 1313C/C/1212C in COC in CO22 ( (1313C) to help C) to help determine the origin.determine the origin.1313C is a tracer for terrestrial fluxes.C is a tracer for terrestrial fluxes.

CO213C

Ocean

Land

Total

18 – 53 N

Mid-latitudeMid-latitude non-fossil non-fossil Carbon Fluxes Carbon Fluxes

=1.5 Pg (1015g) C

• Changes in the terrestrial biosphere appear to drive the trend.•Biosphere trend is relatively insensitive to C3/C4 and other parameters.

p<0.01p<0.06

Correlation of Flux and Climate Correlation of Flux and Climate AnomaliesAnomalies

Zonally Averaged Climate

r =-0.7r = 0.3

Correlation of Flux and Climate Correlation of Flux and Climate AnomaliesAnomalies

Eurasian Average Climate

r =-0.4

Correlation of Flux and Climate Correlation of Flux and Climate AnomaliesAnomalies

North American Average Climate

r =-0.7

ConclusionsConclusions

1.1. NH carbon sink shrunk from 1992 – NH carbon sink shrunk from 1992 – 2003 by ~1.5 billion tons of C; 2003 by ~1.5 billion tons of C; probably driven by land.probably driven by land.

2.2. Regardless of whether this persists, Regardless of whether this persists, it demonstrates that surface uptake it demonstrates that surface uptake can change rapidly.can change rapidly.

3.3. Analysis of climate anomalies Analysis of climate anomalies hintshints at drought as a driver of variability at drought as a driver of variability in temperate NH.in temperate NH.