The vulnerable ocean: Decadal changes in the ocean carbon and oxygen cycles

Holger Brix1, Curtis Deutsch2, Scott C. Doney3, Arne Koertzinger4, Doug W. R. Wallace4, and Rik Wanninkhof5

Nicolas Gruber

Environmental Physics, Institute of Biogeochemistry and Pollutant Dynamics,ETH Zürich, Switzerland

(1) IGPP, UCLA, Los Angeles, USA; (2) Univ. of Washington, Seattle, USA; (3) WHOI, Woods Hole, USA; (4) Leibniz Inst. for Marine Sciences, GER; (5) NOAA AOML, Miami, USA.

1955-1998: Rate of 3.3x1021 J yr-1 = 0.2 W m-2 = 0.1 PW

APPA

REN

T O

XYG

EN

UTIL

IZA

TIO

NAAIW

MED

LAB

AAIW

NADW

MED

STMW

NADW

LAB

SPMW

SPMW

AOU = [O2sat] - [O2]

AO

U C

HA

NG

ES

20

03

-19

93

AO

U A

ND

DIC

CH

AN

GES

200

3-1

993

Expected change from anthropogenic CO2: max 0-8 mol/kg

IMBER-SOLAS CO2/CLIVAR Repeat Hydrography Program

status ~2005

ARGO: The next generation observing system

A global array of profiling floats that measure the temperature and

salinity of the upper 2000 m on a ~10 day repeat cycle.

How to get oxygen on ARGO floats: Promising oxygen sensors

Electrochemical sensor(Seabird SBE 43/IDO)

Optode sensor (Aanderaa 3830)

Measurement range:120% of surface saturation

Initial accuracy:2% of saturation

Response time:6 s (e-folding time)

Measurement range:0-120% of surface saturation(0-500 µM)

Precision:<1 µM (0.4%)

Initial accuracy:8 µM or 5% (whichever is greater)

Response time:25 s (63% e-folding time)

Principle: Life time based dynamic fluorescence quenching

Principle: Clark-type polarographic membrane sensor

UW floats(S. Riser)

Summary & Outlook

• Oxygen concentrations in the thermocline of the North Atlantic have decreased substantially over the last decade, accompanied by a faster than expected increase in DIC.

• The records are too short to attribute these changes to anthropogenic climate change or to natural variability.

• Oxygen is a very sensitive tracer for studying and understanding the response of ocean biogeochemistry to climate variability and global climate change.

• Most of these changes are likely due to a reduction in the circulation rate of thermocline waters, possibly related to the predominantly positive phase of NAO during the 1990s.

The End.

Apparent Oxygen Utilization

AOU = O2sat -O2

ΔO2 = ΔO2sat - ΔAOU

Fundamentals

(σθ)

σθ 26.8

σθ 26.4

(σθ )

DIC

CH

AN

GES

200

3-1

993