WHOI Calcification Workshop May 2001 Organic Carbon Remineralization and Calcium Carbonate Dissolution in the North Pacific Ocean R.A. Feely, C. L. Sabine, K. Lee, F.J. Millero, M. F. Lamb, J.L. Bullister, R.M. Key, R. Wanninkhof , T.-H. Peng, and A.

1
CLIVAR/CO2 Repeat Hydrography
R.A. Feely, C.L. Sabine, R. Wanninkhof, G.C.
Johnson, J.L. Bullister, M. Barringer, C.W.
Mordy, J.-Z. Zhang, M.F. Lamb, D. Greeley, F.J.
Millero, A.G. Dickson, Nicolas Gruber, Robert
H. Byrne and Aleck Wang
Goal
To quantify decadal changes in the inventory and
transport of heat, fresh water, carbon dioxide
(CO2), chlorofluorocarbon tracers and related
parameters in the oceans.
Approach
The sequence and timing of the CLIVAR/CO2 Repeat
Hydrography cruises have been selected so that
there is roughly a decade between them and the
WOCE/JGOFS global survey.
Achievements
The U.S. CLIVAR/CO2 Repeat Hydrography Program
has completed 6 of 19 cruises and is on schedule.
Global map of planned CLIVAR/CO2 Repeat
Hydrography Program hydrographic sections
http//ushydro.ucsd.edu/
2
Outline

• Present an overview changes in inorganic carbon
  (DIC)
• and related physical (CFC-12) and
  biogeochemical
• parameters (AOU and NO3) in the Atlantic and
  Pacific.

• Describe changes in DIC and AOU discuss
  implications.

• Provide an estimate of changes in inorganic
  carbon and
• anthropogenic carbon uptake and uncertainties
  therein.

• Discuss implications for future planning.

COP Annual Review 25-27 May 2005
3

• Concerns about how to obtain the decadal signal
  of anthropogenic CO2 in the ocean?
• ?DIC ? Canthro Intrinsic changes Climate
  induced changes
• Intrinsic and climate induced changes can be
  about the same order of magnitude as ? Canthro.
• Decrease in ventilation in upper thermocline of
  high and mid-latitude waters in N-Atlantic and
  North Pacific resulting in generally greater AOU
  and NO3 levels.
• Redfield stoichiometry is not always applicable
  since some of O2 changes are caused by changes in
  ventilation.
• Conventional analytical approaches to determine ?
  Canthro can be problematic and assumption in
  methods should be investigated and supported with
  modeling efforts.
• Need for higher resolution data in some regions.

COP Annual Review 25-27 May 2005
4
WOCE/JGOFS/OACES Global CO2 Survey
72,000 sample locations collected in the 1990s
DIC 2 µmol kg-1 TA 4 µmol kg-1
Mapped Inventory 10617 Pg C
marginal seas 6 6 Pg C
Arctic Ocean 6 6 Pg C
Total Inventory 11819 Pg C
Sabine et al (2004).
5
We must understand the temporal and spatial
changes of the global ocean carbon system and the
feedbacks to the climate system.
CLIVAR/CO2 Repeat Hydrography Program
6
Water Mass Formation Regions
Anthropogenic CO2 moves into the ocean interior
with mode, intermediate, deep and bottom water.
The highest inventories are found in areas where
water is sinking into the ocean interior taking
with it the anthropogenic CO2 accumulated at the
surface.
7
Figure supplied by Curtis Deutsch
8
Expected changes in surface ocean due to
increased atmospheric burden 11.6
µmol/kg (A16N decade) (18.6/11.88 ppm CO2 Mauna
Loa Revelle Factor 9.7 DIC 2059 pCO2(20)
347 T 20.8)
Equilibrium surface water CO2 increase
Atmospheric CO2 increase
9
Repeat Cruises in the Atlantic A16N 1988
OC202-AOU, CFC-12 1993 NA93-DIC 2003 A16N-AOU,
CFC-12, DIC A16S 1989 HYDROS4- AOU, CFC-12,
DIC 1989 Save5- AOU, CFC-12, DIC 2005 A16S-
AOU, CFC-12, DIC A22 August-September
1997 October-November 2003 A20 July-August
1997 August-September 2003
10
High-resolution tracers in the Atlantic Ocean
All transects show excellent precision pCFC
0.005 pmol kg-1 AOU 1-2 µmol kg-1 DIC 1-2
µmol kg-1
11
Decadal changes in the Atlantic Ocean

• All transects show
• regions in the upper thermocline with
• CFC-12 changes gt 0.9 pmol kg-1
• AOU changes gt 20 µmol kg-1
• DIC changes gt 30 µmol kg-1
• Greater than expected changes due to
• Movement of fronts/eddies
• watermasses
• Changes in ventilation
• Changes in remineralization

12
A16N upper thermocline 26.8- 27.4
Causes of AOU changes ?DIC ? Canthro
Intrinsic changes Climate changes
O2/NO3
? NO3
? AOU
Greater O2 change
Greater NO3 change
NO3/ O2 16/170 0.094
If a canonical RNO stoichiometry holds,
remineralization cannot solely account for
changes in AOU
13
A16N upper thermocline 26.8- 27.4

• Multiparameter Linear Regression (MLR) technique
  gt15 N
• DIC(1993) a1 b1 T c1 S d1 AOU e1 NO3
• DIC(2003) a2 b2 T c2 S d2 AOU e2 NO3
• n3000, r2 0.98, standard error DIC 5
  µmol/kg
• E-MLR ?DIC (2003-1993) a2-1 b2-1 T c2-1 S
  d2-1 AOU e2-1 NO3
• Canthro (using 2003 T, S, AOU,
  NO3 data)

14

• Specific inventories A16N (gt 15 N)
• Large spatial variations in ?DIC
• Overcorrection using AOU
• MLR- no bottom water residual

Bin-averaged depth plots with smoothed curve
15
Higher throughput Using USF Seas Technology
Robert H. Byrne and Aleck Wang, USF
16
WOCE/JGOFS Global CO2 Survey
Portion of P16 covered by this cruise
includes P16S/P17S August 1991 P16A/P17A
October 1992 S4P March 1992
17
SAF
ACCF
18
SAF
ACCF
19
WOCE/JGOFS Global CO2 Survey
P2 Repeat cruise dates P2 July-August 1994 P2
July-August 2004
20
North Pacific DIC Changes (2004 - 1994)
MLR Procedure
Large positive DIC differences in surface waters
and 10 - 37 µmol/kg increases at intermediate
depths between 200 - 800m.
COP Annual Review 25-27 May 2005
21
?CANTH
?CANTH ?CMEAS - ?CORG - ?CTALK
2004 - 1994 P2 Repeat Hydrographic Section
Difference
COP Annual Review 25-27 May 2005
22
?CORG
?CORG (117/170) (AOU2004 - AOUCALC(MLR1994))
2004 - 1994 P2 Repeat Hydrographic Section
Difference
RC/O 0.688 from Anderson and Sarmiento (1994)
COP Annual Review 25-27 May 2005
23
?CTALK
?CTALK 0.5 (TALKMEAS TALKCALC(MLR1994))
2004 - 1994 P2 Repeat Hydrographic Section
Difference
COP Annual Review 25-27 May 2005
24
CO2 Growth Rate on Isopycnal Surfaces along 30N
Based on P2 2004 - 1994 Comparison
25
Carbon Increases in the Pacific and Atlantic
Oceans
Integrated uptakerate (mol m2 yr-1) Mixed layer uptake(µmol kg-1 yr-1) pCO2 increase (µatm yr-1) Approach Area of Study Years Depth Range (m) Reference
0.7 0.2 -- -- MLR North Atlantic 1993-2003 0-5000 This work
-- -- -- -- South Atlantic 1989-2005 0-5000 This Work
1.0 0.6 O.6 0.4 1.2 0.5 MLR, Obs North Pacific 1973-2004 0-1200 Sabine et al., (2004) Takahashi et al., (in prep)
-- -- -- MLR, Obs South Pacific 1993-2005 0-5000 This Work
COP Annual Review 25-27 May 2005
26
Deutsch and Thompson O2 changes (relative to
1960s)
27
Causes of oxygen change (1990s-1980s) sq 26.6
a)
b)
d)
c)
28
Conclusions

• Air-sea exchange, ventilation, and circulation
  processes are the
• primary control of the DIC increases in the
  surface and
• intermediate waters of the Atlantic and
  Pacific Oceans.

• We have observed mixed layer and intermediate
  water DIC
• increases ranging from 0.4 - 2.2 µmol kg-1
  yr-1 over the past
• decade, with significant regional
  differences.

• Changes in circulation cause significant decadal
  changes in DIC,
• but we must be able to distinguish natural
  process from climate
• change effects.

COP Annual Review 25-27 May 2005
29
Recommendations

• Increase Repeat Hydrography sample coverage in
  regions
• where active ventilation is occurring.

• Test new methods for high-resolution O2 and CO2
  profiling on
• Repeat Hydrography cruises. Provide support for
  profiling
• O2 and CO2 measurements.

• Develop basin-scale carbon models that accurately
  reproduce
• gas exchange, ventilation and
  biogeochemical processes.

• 4. Support international efforts for data
  synthesis and exchange.

COP Annual Review 25-27 May 2005
30
Onto our Next Cruise - P16N in 2006!