Ocean Carbon Dioxide Uptake in the Tailpipe of Industrialized Continents

Palter, J. B.; Nickford, S.; Mu, L.

doi:10.1029/2023gl104822

Cited by 3 publications

(2 citation statements)

References 22 publications

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“…This systematic bias in wind speed translates to an 8% underestimate in the air‐sea CO 2 flux when using the ERA‐5 product in place of in situ wind speeds. The low bias increases to 9% when wind speed and significant wave height from ERA‐5 and the MBL zonal mean atmospheric p CO 2 product are used in place of in situ data, signaling that the true atmospheric p CO 2 is higher than its zonal mean in this region downwind of North America (Palter et al., 2023). These biases are similar as a percentage error whether using a wind‐only gas transfer velocity (e.g., Ho et al., 2006; Wanninkhof, 2014) or one that uses significant wave height to parameterize the bubble‐mediated flux (Deike & Melville, 2018), while the difference in average flux between these two gas transfer velocities is over 25%.…”

Section: Discussionmentioning

confidence: 99%

The Importance of Contemporaneous Wind and pCO₂ Measurements for Regional Air‐Sea CO₂ Flux Estimates

Nickford,

Palter,

2024

JGR Oceans

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Few observational platforms are able to sustain direct measurements of all the key variables needed in the bulk calculation of air‐sea carbon dioxide (CO2) exchange, a capability newly established for some Uncrewed Surface Vehicles (USVs). Western boundary currents are particularly challenging observational regions due to strong variability and dangerous sea states but are also known hot spots for CO2 uptake, making air‐sea exchange quantification in this region both difficult and important. Here, we present new observations collected by Saildrone USVs in the Gulf Stream during the winters of 2019 and 2022. We compared Saildrone data across co‐located vehicles and against the Pioneer Array moorings to validate the data quality. We explored how CO2 flux estimates differ when all variables needed to calculate fluxes from the bulk formulas are simultaneously measured on the same platform, relative to the situation where in situ observations must be combined with publicly‐available data products. We systematically replaced variables in the bulk formula with those often used for local and regional flux estimates. The analysis revealed that when using the ERA‐5 reanalysis wind speed in place of in situ observations, the ocean uptake of CO2 is underestimated by 8%; this underestimate grows to 9% if the NOAA Marine Boundary Layer atmospheric CO2 product and ERA‐5 significant wave height are also used in place of in situ observations. Overall our findings point to the importance of collecting contemporaneous observations of wind speed and ocean pCO2 to reduce biases in estimates of regional CO2 flux, especially during high wind events.

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Section: Discussionmentioning

confidence: 99%

The Importance of Contemporaneous Wind and pCO₂ Measurements for Regional Air‐Sea CO₂ Flux Estimates

Nickford,

Palter,

2024

JGR Oceans

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“…We assume that the uncertainty in our air-sea CO 2 flux estimate results from a 20% uncertainty in k (Wanninkhof, 2014) and the overall product uncertainty in estimated pCO 2 (θpCO 2 ; Section 3.3 below). As the uncertainty of ΔpCO 2 is dominated by the uncertainty in estimated surface ocean pCO 2 , we neglect the contribution from atmospheric CO 2 despite potential point source effects nearshore (Palter et al, 2023). In our study area there are minimal industrial sources along much of the coastline, prevailing westerlies, monthly averaging, and air-sea disequilibrium is most often large nearshore (e.g., Salish Sea; Section 5.1).…”

Section: Computation Of Air-sea Fluxesmentioning

confidence: 99%

High‐Resolution Neural Network Demonstrates Strong CO₂ Source‐Sink Juxtaposition in the Coastal Zone

Duke,

Hamme,

Ianson

et al. 2024

JGR Oceans

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The role of coastal oceans in regulating atmospheric carbon dioxide remains poorly quantified and understood. Here, we use a two‐step neural network approach to generate estimates from sparse observational data in the coastal Northeast Pacific Ocean at an unprecedented spatial resolution of 1/12° with coverage in the nearshore (0–25 km offshore). We compiled partial pressure of carbon dioxide (pCO2) observations as well as a range of predictor variables including satellite‐based and physical oceanographic reanalysis products. With the predictor variables representing processes affecting pCO2, we created non‐linear relationships to interpolate observations from 1998 to 2019. Compared to in situ shipboard and mooring observations, our coastal pCO2 product captures broad spatial patterns and seasonal cycle variability well. A sensitivity analysis identifies that the parameters responsible for the neural network's ability to capture regional pCO2 variability are associated with mechanistic processes, including mixed layer deepening, mesoscale eddies, and gyre upwelling. Using wind speed and atmospheric CO2, we calculated air‐sea CO2 fluxes. We report an anticorrelation between annual air‐sea CO2 flux and its seasonal amplitude with the relationship driven by circulation, opposing seasonal upwelling/relaxation versus downwelling, and the effects of winter mixing and primary productivity. We show that the inclusion of nearshore net outgassing fluxes lowers the overall regional net flux. Overall, our results suggest that the region is a net sink (−0.7 mol m−2 yr−1) for atmospheric CO2 with trends indicating increasing oceanic uptake due to strong connectivity to subsurface waters.

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High‐Resolution Variability of the Ocean Carbon Sink

Gregor,

Shutler,

Gruber

2024

Global Biogeochemical Cycles

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Measurements of the surface ocean fugacity of carbon dioxide (fCO2) provide an important constraint on the global ocean carbon sink, yet the gap‐filling products developed so far to cope with the sparse observations are relatively coarse (1° × 1° by 1 month). Here, we overcome this limitation by using a novel combination of machine learning‐based methods and target transformations to estimate surface ocean fCO2 and the associated sea‐air CO2 fluxes (FCO2) globally at a resolution of 8‐day by 0.25° × 0.25° (8D) over the period 1982 through 2022. Globally, the method reconstructs fCO2 with accuracy similar to that of low‐resolution methods (∼19 μatm), but improves it in the coastal ocean. Although global ocean CO2 uptake differs little, the 8D product captures 15% more variance in FCO2. Most of this increase comes from the better‐represented subseasonal scale variability, which is largely driven by the better‐resolved variability of the winds, but also contributed to by the better‐resolved fCO2. The high‐resolution fCO2 is also capable of capturing the signal of short‐lived regional events such as hurricanes. For example, the 8D product reveals that fCO2 was at least 25 μatm lower in the wake of Hurricane Maria (2017), the result of a complex interplay between the decrease in temperature, the entrainment of carbon‐rich waters, and an increase in primary production. By providing new insights into the role of higher frequency variations of the ocean carbon sink and the underlying processes, the 8D product fills an important gap.

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Ocean Carbon Dioxide Uptake in the Tailpipe of Industrialized Continents

Cited by 3 publications

References 22 publications

The Importance of Contemporaneous Wind and pCO₂ Measurements for Regional Air‐Sea CO₂ Flux Estimates

The Importance of Contemporaneous Wind and pCO₂ Measurements for Regional Air‐Sea CO₂ Flux Estimates

High‐Resolution Neural Network Demonstrates Strong CO₂ Source‐Sink Juxtaposition in the Coastal Zone

High‐Resolution Variability of the Ocean Carbon Sink

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Ocean Carbon Dioxide Uptake in the Tailpipe of Industrialized Continents

Cited by 3 publications

References 22 publications

The Importance of Contemporaneous Wind and pCO2 Measurements for Regional Air‐Sea CO2 Flux Estimates

The Importance of Contemporaneous Wind and pCO2 Measurements for Regional Air‐Sea CO2 Flux Estimates

High‐Resolution Neural Network Demonstrates Strong CO2 Source‐Sink Juxtaposition in the Coastal Zone

High‐Resolution Variability of the Ocean Carbon Sink

Contact Info

Product

Resources

About

The Importance of Contemporaneous Wind and pCO₂ Measurements for Regional Air‐Sea CO₂ Flux Estimates

The Importance of Contemporaneous Wind and pCO₂ Measurements for Regional Air‐Sea CO₂ Flux Estimates

High‐Resolution Neural Network Demonstrates Strong CO₂ Source‐Sink Juxtaposition in the Coastal Zone