A 17-year dataset of surface water fugacity of CO₂ along with calculated pH, aragonite saturation state and air–sea CO₂ fluxes in the northern Caribbean Sea

A high-quality dataset of surface water fugacity of CO2 (fCO2w)1, consisting of over a million observations, and derived products are presented for the northern Caribbean Sea, covering the time span from 2002 through 2018. Prior to installation of automated pCO2 systems on cruise ships of Royal Caribbean International and subsidiaries, very limited surface water carbon data were available in this region. With this observational program, the northern Caribbean Sea has now become one of the best-sampled regions for pCO2 of the world ocean. The dataset and derived quantities are binned and averaged on a 1∘ monthly grid and are available at http://accession.nodc.noaa.gov/0207749 (last access: 30 June 2020) (https://doi.org/10.25921/2swk-9w56; Wanninkhof et al., 2019a). The derived quantities include total alkalinity (TA), acidity (pH), aragonite saturation state (ΩAr) and air–sea CO2 flux and cover the region from 15 to 28∘ N and 88 to 62∘ W. The gridded data and products are used for determination of status and trends of ocean acidification, for quantifying air–sea CO2 fluxes and for ground-truthing models. Methodologies to derive the TA, pH and ΩAr and to calculate the fluxes from fCO2w temperature and salinity are described.

A17-year dataset of surface water fugacity of CO₂, along with calculated pH, Aragonite saturation state, and air-sea CO₂ fluxes in the Northern Caribbean Sea

A high-quality dataset of surface water partial pressure/fugacity of CO2 (pCO2w/fCO2w), comprised of over a million observations, and derived products are presented for the Caribbean Sea covering the timespan from 2002 through 2018. Prior to installation of automated pCO2 systems on cruise ships of the Royal Caribbean Cruise Lines and subsidiaries, very limited surface water carbon data were available in this region. With this observational program, the Northern Caribbean Sea has now become one of the best sampled regions for pCO2 of the world's ocean. The dataset, and derived quantities are provided on a 1-degree monthly grid at http://accession.nodc.noaa.gov/0207749, DOI: https://doi.org/10.25921/2swk-9w56 (Wanninkhof et al., 2019a). The derived quantities include total alkalinity (TA), acidity (pH), Aragonite saturation state (ΩAr) and air-sea CO2 flux, and cover the region from 15° N to 28° N and 88° W to 62° W. The data and products are used for determination of status and trends of ocean acidification, for quantifying air-sea CO2 fluxes, and for ground truthing models. Methodologies to derive the inorganic carbon system parameters and to calculate the fluxes from fCO2w are described.

Experimental grain growth of quartz aggregates under wet conditions and its application to deformation in nature

Grain growth of quartz was investigated using two quartz samples (powder and novaculite) with water under pressure and temperature conditions of 1.0–2.5 GPa and 800–1100 ∘C. The compacted powder preserved a substantial porosity, which caused a slower grain growth than in the novaculite. We assumed a grain growth law of dn-d0n=k0fH2Orexp⁡(-Q/RT)t with grain size d (µm) at time t (seconds), initial grain size d0 (µm), growth exponent n, a constant k0 (µmn MPa−r s−1), water fugacity fH2O (MPa) with the exponent r, activation energy Q (kJ mol−1), gas constant R, and temperature T in Kelvin. The parameters we obtained were n=2.5±0.4, k0=10-8.8±1.4, r=2.3±0.3, and Q=48±34 for the powder and n=2.9±0.4, k0=10-5.8±2.0, r=1.9±0.3, and Q=60±49 for the novaculite. The grain growth parameters obtained for the powder may be of limited use because of the high porosity of the powder with respect to crystalline rocks (novaculite), even if the differences between powder and novaculite vanish when grain sizes reach ∼70 µm. Extrapolation of the grain growth laws to natural conditions indicates that the contribution of grain growth to plastic deformation in the middle crust may be small. However, grain growth might become important for deformation in the lower crust when the strain rate is < 10−12 s−1.

Experimental grain growth of quartz aggregates under wet conditions and its application to deformation in nature

The grain growth of quartz was investigated using two samples of quartz (powder and quartzite) with water under pressure and temperature conditions of 1.0–2.5 GPa and 800–1100 °C. The compacted powder preserved a large porosity, which caused a slower grain growth than in the dense quartzite. We assumed a grain-growth law of dn-d0n = k0 fH2Or exp⁡(−Q/RT)t with grain size d (µm) at time t (second), initial grain size d0 (µm), growth exponent n, a constant k0 (µmn MPa−r s−1), water fugacity fH2O (MPa) with the exponent r, activation energy Q (kJ/mol), gas constant R, and temperature T in Kelvin. The parameters we obtained were n = 2.5 ± 0.4, k0 = 10−8.8 ± 1.4, r = 2.3 ± 0.3, and Q = 48 ± 34 for the powder, and n = 2.9 ± 0.4, k0 = 10−5.8 ± 2.0, r = 1.9 ± 0.3, and Q = 60 ± 49 for the quartzite. The grain-growth parameters obtained for the powder may be of limited use because of the high porosity of the powder with respect to crystalline rocks, even if the differences between powder and quartzite vanish when grain sizes reach ~ 70 µm. Extrapolation of the grain-growth laws to natural conditions indicates that the contribution of grain growth to plastic deformation in the middle crust may be small. However, grain growth might become important for deformation in the lower crust when the strain rate is