45
rated with water vapor which mole fraction can be computed from T. Partial pressure, (pCO 2 ) is then computed with knowledge of atmospheric pressure.
Alternatively, dye-based methods rely on equilibrating CO 2 between seawater
and a bromothymol blue dye solution across a gas permeable membrane, thus
changing the pH of the dye solution, and subsequent measurement of its resulting
optical absorption. Color changes are monitored at the diagnostic peaks of 440 and
620 nm referred to a nonabsorbing blank at 715 nm (DeGrandpre et al. 1995).
Current system design allows deployment for up to 1 year autonomous operation
with sampling at hourly intervals. Concurrent deployment of automated pH measuring systems such as those described above allows explicit solution of the carbonate
equilibrium equations discussed above (Grey et al. 2012).
Carbon Dioxide Measurements from Space
Placement in orbit of three satellites capable of measuring atmospheric CO 2 from
space, the Japanese Greenhouse Gas Observing Satellite (GOSAT), launched
in 2009, (https://www.env.go.jp/en/focus/docs/files/20120201-26.pdf accessed
11/13/2017); the US Orbiting Carbon Observatory-2 (OCO-2), launched in 2014,
(Eldering et al. 2017); and the Chinese Carbon Dioxide Observation Satellite
(TanSat) launched in 2016 (Liu et al. 2013), is now affording synoptic views of
spatial atmospheric CO 2 distribution with unprecedented resolution. In general,
spectrometers aboard these satellites measure sunlight reflection by atmospheric
CO 2 in narrow near and mid-IR CO 2 spectral absorption bands. While these satellites do not measure CO 2 in seawater, concurrent in situ measurements can help
refine estimates of sea-air CO 2 exchange. Indeed, Chatterjee et al. (2017) have used
OCO-2 data in conjunction with seawater CO 2 data from NOAA ocean buoys to
unravel the timing of the response of the ocean and the terrestrial carbon cycle during the 2015–2016 El Niño. Regionally pertinent data is afforded by the OCO-2
with a footprint of nominally 1.25 by 2.4 km.
2.3.4 Inorganic Nutrients Dissolved in Seawater
The lovely blue transparent waters of tropical beach resorts owe their pristine look
to their dearth of dissolved inorganic nutrients (plant fertilizer) that makes them
virtual ocean deserts. Productive ocean waters are green and turbid, teeming with
ocean life. The major elements carbon (C), nitrogen (N), and phosphorus (P) are
found in plant material in the molar ratios of 106 to 15 to 1 where they make up the
principal biochemical plant components: sugars, fats, proteins, and nucleic acids.
Living plants require these elements as dissolved inorganic nutrients for growth and
reproduction. While C is plentiful (around 2 mmol.kg
−1
as noted above), N and P are
in short supply in the ocean (rarely exceeding 45 and 3 μmol.kg
−1
, respectively) and
often become limiting for plant growth in stratified surface waters. In nearshore
2.3 Electrochemical Sensors for Coastal Ocean Observing
rated with water vapor which mole fraction can be computed from T. Partial pressure, (pCO 2 ) is then computed with knowledge of atmospheric pressure.
Alternatively, dye-based methods rely on equilibrating CO 2 between seawater
and a bromothymol blue dye solution across a gas permeable membrane, thus
changing the pH of the dye solution, and subsequent measurement of its resulting
optical absorption. Color changes are monitored at the diagnostic peaks of 440 and
620 nm referred to a nonabsorbing blank at 715 nm (DeGrandpre et al. 1995).
Current system design allows deployment for up to 1 year autonomous operation
with sampling at hourly intervals. Concurrent deployment of automated pH measuring systems such as those described above allows explicit solution of the carbonate
equilibrium equations discussed above (Grey et al. 2012).
Carbon Dioxide Measurements from Space
Placement in orbit of three satellites capable of measuring atmospheric CO 2 from
space, the Japanese Greenhouse Gas Observing Satellite (GOSAT), launched
in 2009, (https://www.env.go.jp/en/focus/docs/files/20120201-26.pdf accessed
11/13/2017); the US Orbiting Carbon Observatory-2 (OCO-2), launched in 2014,
(Eldering et al. 2017); and the Chinese Carbon Dioxide Observation Satellite
(TanSat) launched in 2016 (Liu et al. 2013), is now affording synoptic views of
spatial atmospheric CO 2 distribution with unprecedented resolution. In general,
spectrometers aboard these satellites measure sunlight reflection by atmospheric
CO 2 in narrow near and mid-IR CO 2 spectral absorption bands. While these satellites do not measure CO 2 in seawater, concurrent in situ measurements can help
refine estimates of sea-air CO 2 exchange. Indeed, Chatterjee et al. (2017) have used
OCO-2 data in conjunction with seawater CO 2 data from NOAA ocean buoys to
unravel the timing of the response of the ocean and the terrestrial carbon cycle during the 2015–2016 El Niño. Regionally pertinent data is afforded by the OCO-2
with a footprint of nominally 1.25 by 2.4 km.
2.3.4 Inorganic Nutrients Dissolved in Seawater
The lovely blue transparent waters of tropical beach resorts owe their pristine look
to their dearth of dissolved inorganic nutrients (plant fertilizer) that makes them
virtual ocean deserts. Productive ocean waters are green and turbid, teeming with
ocean life. The major elements carbon (C), nitrogen (N), and phosphorus (P) are
found in plant material in the molar ratios of 106 to 15 to 1 where they make up the
principal biochemical plant components: sugars, fats, proteins, and nucleic acids.
Living plants require these elements as dissolved inorganic nutrients for growth and
reproduction. While C is plentiful (around 2 mmol.kg
−1
as noted above), N and P are
in short supply in the ocean (rarely exceeding 45 and 3 μmol.kg
−1
, respectively) and
often become limiting for plant growth in stratified surface waters. In nearshore
2.3 Electrochemical Sensors for Coastal Ocean Observing