The air-sea flux of carbon dioxide for the Chesapeake Bay

Alana Menendez

Outward flux = akw(pCO2,w – pCO2,a)

• T = temperature, S = salinity• a = carbon dioxide solubility in water = f(T, S,

total air pressure)• U = wind speed• kw = gas transfer velocity = f(U, T, S)

• pCO2,a= atmospheric pCO2 (known)

• pCO2,w= surface water pCO2 = f(T, S, alkalinity, pH)

20 weighted stations in nine subregions

Northern CB

Central CB

Southern CB

Eigen Vector Analysis from PCA for flux data

Eigen Vector Analysis from PCA for pCO2,w data

• Gas transfer velocity (Kw): Component 1 accounted for 79.6% of variance

• Solubility (a ): Component 1 accounted for 98.7% of variance• pCO2,a: Component 1 accounted for 99.9% of variance

Markov Chains

• Does a positive or negative carbon dioxide flux for the next month depend on that of the current month?

• Negative flux=0; Positive flux=1

Region Lag 1 Lag 21 0.4013 0.16712 0.2144 0.08633 0.1953 0.11744 0.2267 0.11675 0.3577 0.17416 0.4809 0.24527 0.413 0.28358 0.3781 0.24219 0.3883 0.2168

Testing significance of Slope/ Trendline

• Null hypothesis:b=0

• t= -1.8812• Test level= 5%• p=0.0354• p<0.05 so we reject

the null hypothesis

Conclusions from Analysis

• PCA analysis reveals differences in CO2 flux between the northern and southern Chesapeake Bay in component 2.

• PCA reveals differences in CO2 flux between the central and northern/southern CB in component 3.

• pCO2,w may be the parameter that is able to account for CO2 flux differences between subregions the most.

• Over 29 years, the trendline is significant: needs to be determined for all 9 subregions.