The roles of (physical and) biological
processes in determining oxygen and
pH levels in the
eastern Pacific Oceans
Francisco Chavez, Gernot Friederich,
Monique Messie, Jeff Sevadjian
Monterey Bay Aquarium Research Institute (MBARI)
Funding from David and Lucile Packard Foundation, NASA, and NOAA
Physics sets the boundaries, biology gets it done, chemistry results
Key message
• In the eastern Pacific Ocean, photosynthesis
and respiration strongly regulate surface
(and subsurface) ocean oxygen and pH –
two examples and speculation about future
Explain average delta pCO2 from Alaska to Chile
Intertidal
Low O2
Source water
,NO3
Chavez et al.
2006
Biology leaves a strong imprint on chemistry
SST
On a day (photosynthesis) night (respiration) cycle pH variations are an
order of magnitude larger than annual rate of acidification
Mooring
Intertidal
Primary production up to 2 grams carbon per m3
Large database of delta pCO2 from Alaska to Chile
Surface NO3 from WOA - DeltaN
+ O2
For carbon add an age
component using CFCs
to get initial pCO2
Preformed nitrate using AOU from WOA
Background is Chapter in the State of the Carbon Cycle
Report (SOCCR) where air-sea flux measurements
around North America were synthesized and a net flux
of 19 Teragrams of C per year out of ocean estimated
Chavez, F.P., T. Takahashi, W.-J. Cai, G. Friederich, B. Hales, R. Wanninkhof, and R.A. Feely (2007)
Coastal Oceans. In: The First State of the Carbon Cycle Report (SOCCR): The North American
Carbon Budget and Implications for the Global Carbon Cycle. A Report by the U.S. Climate Change
Science Program and the Subcommittee on Global Change Research[King, A.W., L. Dilling, G.P.
Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)].
National Oceanic and Atmospheric Administration, National Climatic Data Center, Asheville, NC, USA,
pp. 157-166.
MBARI
DATA
Space
LDEO
514977
MBARI
1448132
SOCAT
326571
Time
Season
High latitude sink
Tropical Source
44 TgC per year source
Not significantly different from 0
r = 0.57
Surface nitrate from WOA
r = 0.86
What happens if we remove biology?
What happens if we remove biology?
What will happen in the future?
Chlorophyll
Model
SeaWiFS
Chavez et al. 2011
San Diego to Monterey
Colder
More productive
Less oxygen
Oxygen
1990
2000
2010
More giantchange
squid
Ecosystem
pCO2
More CO2
pH
Lower pH
1990
1995
2000
2005
1992
2000
2010
Long term changes in oxygen
Deustch et al. 2011
2012
2003
Lower O2
Difference
Increased productivity and flux (more respiration at depth)
A corollary is that carbon, nitrogen and oxygen
are related so that a decrease in oxygen is
associated with an increase in carbon dioxide
and nitrate (in the source waters for upwelling)
Lower “ventilation” from oxygen rich high latitudes, either
from natural variability or a warmer world
Higher nitrate as well
Conclusions
• Southern hemisphere undersampled
• Southeastern tropical Pacific source
• High latitude sink
• Net flux is small (~0), trending positive
• Preformed nitrate and biological uptake
explain 74% of the variance in delta pCO2
• Photosynthesis (and respiration) regulate
ocean chemistry
• A no brainer: a healthy ocean is critical!