Factors contributing to variability in pCO2 and omega

in the coastal Gulf of Maine.

J. Salisbury, D. Vandemark, C. Hunt, C. Sabine, S. Musielewicz and others

Terms for discussion: pCO2 and Ω

pCO2 – partial pressure of carbon dioxide (μatm) = CO2 concentration / solubility (k)

Omega () – Saturation index of the mineral aragonite

In terms of Ocean Acidification, the Gulf of Maine is an interesting place.

Big salinity rangeFreshwater endmember qualitiesBig temperature rangeVery productive

Two freshwater sources: both poorly buffered

DFO, Canada

Big seasonal temperature range > 15° C /year

DFO, Canada

During the growing season

High CO2

Low CO2

From Bozac et al., 2006 (North Sea Example)

During the mixing season

High CO2

High CO2

CO2

?

Coastal GOM highly productive and…..

both the surface and deep waters interact with the atmosphere over short time scales(~annual).

UNH time series stations in the Gulf of Maine

Data shown is primarily from the CO2 buoy,

with supporting pCO2 and bottle data from cruise stations (red)

xCO2

aragonite

Decadal variability: Do we observe OA from increased atm CO2?

Preliminary analyses on raw data

Mauna Loa was +2.2 ppm y-1 during this time

Note that omega and xCO2 are both positive!

SST +0.2°C y-1

xCO2

Omega_ar

Decadal variability from > atm CO2 ….. maybe!

+/- 0.34

+/- 0.001

Daily-to-seasonal variability in pCO2

δpCO2Observed = δpCO2

SOL + δpCO2AS + δpCO2

H + δpCO2V + δpCO2

NCP*  

Analysis of daily-seasonal pCO2 variability in the context of a time resolving 1-d model

Account for daily change in pCO2 within the mixed layer caused by the processes below: (units, change in pCO2 d-1)

Change induced by changes in solubility, f(temp, salinity)

Change attributable to air sea flux of CO2 out/in of mixed layer: f(wind, delta CO2, MLD)

Net change from horizontal mixing:

f(pCO2 gradient *time)

Net change from vertical mixing: f(ΔMLD, diffusion)

Biology: the residual of (observed – sum of modeled terms)

Similar to 1d models used by Shadwick et al, 2011 and Gruber et al, 1999

Model results:

changes in solubility > 3 atm d-1

Air-sea flux > 4 atm d-1

Model results:

Vertical processes > 4atm d-1

horizontal processes > 5atm d-1

Net biological processes> 5atm d-1

High frequency changes:

often > 20 atm d-1

individual components >10atm d-1

All components subject to future change

- hydrology - net warming- mixing- wind variability

Finally, use daily averaged pCO2

output to explore the components of seasonal variability

A seasonal cycle of controls on pCO2

Conclusions:

Changes in solubility, a-s flux, mixing, NCP, freshwater flux all significant sources of pCO2 and omega variability!!

Results indicate a system that works on an annual frequency, but changes at daily – monthly time step.

Unresolved issues:

Have not yet characterized the natural variability of the carbonate system in the Gulf of Maine!!!

Short term events important (storms, floods, NCP)

Effect of circulation and freshwater sourcing.

Apparent NCP in early summer?

Thanks:

Arctic-COLORS is a Field Campaign Scoping Study funded by NASA's Ocean Biology and Biogeochemistry Program that aims to improve understanding and prediction of land-ocean interactions in a rapidly changing Arctic coastal zone, and assess vulnerability, response, feedbacks and resilience of coastal ecosystems, communities and natural resources to current and future pressures.

Deliverable: a comprehensive report to NASA outlining the major scientific questions, and developing the initial study design and implementation concept for this new campaign

Focus on coastal ocean processes

A needed linkage between field campaigns focusing on the Arctic open ocean environment (e.g. ICESCAPE), and field activities focusing on Arctic river processes, chemistry and fluxes (e.g. ABoVE)

Overarching objective: better understand the impact of climate change on land-ocean interactions in the Arctic Ocean, and examine the effect of these changes on river-dominated coastal ocean biology, biogeochemistry, biodiversity.

Coastal Land Ocean Interactions

Arctic