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Aragonite dissolution kinetics and calcite/aragonite ratios in sinking and suspended particles in the North Pacific

Dong, Sijia and Berelson, William M. and Rollins, Nick E. and Subhas, Adam V. and Naviaux, John D. and Celestian, Aaron J. and Liu, Xuewu and Turaga, Nitya and Kemnitz, Nathaniel J. and Byrne, Robert H. and Adkins, Jess F. (2019) Aragonite dissolution kinetics and calcite/aragonite ratios in sinking and suspended particles in the North Pacific. Earth and Planetary Science Letters, 515 . pp. 1-12. ISSN 0012-821X. http://resolver.caltech.edu/CaltechAUTHORS:20190322-142418170

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Abstract

The lack of consensus on CaCO_3 dissolution rates and calcite to aragonite production and export ratios in the ocean poses a significant barrier for the construction of global carbon budgets. We present here a comparison of aragonite dissolution rates measured in the lab vs. in situ along a transect between Hawaii and Alaska using a ^(13)C labeling technique. Our results show a general agreement of aragonite dissolution rates in the lab versus in the field, and demonstrate that aragonite, like calcite, shows a non-linear response of dissolution rate as a function of saturation state (Ω). Total carbon fluxes along the N. Pacific transect in August 2017, as determined using sediment traps, account for 11∼23 weight % of total mass fluxes in the upper 200 m, with a PIC (particulate inorganic carbon) /POC (particulate organic carbon) mole ratio of 0.2∼0.6. A comparison of fluxes at depths of 100 m and 200 m indicates that 30∼60% PIC dissolves between these depths with 20∼70% attenuation in POC fluxes. The molar ratio of PIC to POC loss is 0.29. The simultaneous loss of PIC and POC in the upper 200 m potentially indicates PIC dissolution driven by organic matter respiration, or metazoan/zooplankton consumption. The calcite/aragonite ratio in trap material is significantly lower in the subtropical gyre than in the subarctic gyre. Aragonite fluxes vary from 0.07 to 0.38 mmol m^(−2) day^(−1) at 100 m, and 0.06 to 0.24 mmol m^(−2) day^(−1) at 200 m along the North Pacific transect, with no specific trend over latitude. The identification of suspended PIC mineral phases by Raman spectroscopy shows the presence of aragonite below 3000 m in the subtropical gyre, but none in the subpolar gyre. These multiple lines of evidence suggest that predictions based on a strictly thermodynamic view of aragonite dissolution, combined with measured aragonite fluxes, underestimate observed alkalinity excess and measured PIC attenuation in sinking particles. Our measured aragonite flux combined with our inorganic dissolution rate only account for 9% and 0.2% of the excess alkalinity observed in the North Pacific (Feely et al., 2004), assuming aragonite sinking rates of 1 m day^(−1) and 100 m day^(−1), respectively. However, respiration-driven dissolution or metazoan/zooplankton consumption, indicated by the simultaneous attenuation of PIC and POC in sediment traps, is able to generate the magnitude of dissolution suggested by observed excess alkalinity.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.epsl.2019.03.016DOIArticle
https://www.sciencedirect.com/science/article/pii/S0012821X19301645PublisherArticle
ORCID:
AuthorORCID
Dong, Sijia0000-0002-5811-9333
Subhas, Adam V.0000-0002-7688-6624
Celestian, Aaron J.0000-0003-0775-6380
Additional Information:© 2019 Elsevier B.V. Received 8 November 2018, Revised 8 March 2019, Accepted 10 March 2019, Available online 22 March 2019. This work was supported by NSF Ocean Acidification grants (numbers OCE1220600 and OCE1220302), USC Dornsife Doctoral Fellowship, Elizabeth and Jerol Sonosky Fellowship, the Sea Grant Fellowship, and the Resnick Sustainability Institute Graduate Fellowship. The authors would like to acknowledge editor Derek Vance, reviewer Jack Middelburg and another anonymous reviewer for their invaluable comments of the original manuscript. We thank the captain and crews on Kilo Moana for their assistance at sea. We also acknowledge Christopher Moore, Loraine Martell-Bonet for their help measuring pH and alkalinity during CDisK-IV; Yi Hou for leak-checking the Niskin Incubators by measuring dissolved Si concentrations; Doug Hammond for providing the in situ pumps; Johnny Stutsman and James Rae for their help deploying and recovering in situ pumps; as well as Abby Lunstrum and Huanting Hu for their help picking out swimmers from the sediment trap samples.
Group:Resnick Sustainability Institute
Funders:
Funding AgencyGrant Number
NSFOCE-1220600
NSFOCE-1220302
University of Southern CaliforniaUNSPECIFIED
Elizabeth and Jerol Sonosky FellowshipUNSPECIFIED
Sea Grant FellowshipUNSPECIFIED
Resnick Sustainability InstituteUNSPECIFIED
Subject Keywords:aragonite dissolution rate; calcite/aragonite ratio; North Pacific
Record Number:CaltechAUTHORS:20190322-142418170
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20190322-142418170
Official Citation:Sijia Dong, William M. Berelson, Nick E. Rollins, Adam V. Subhas, John D. Naviaux, Aaron J. Celestian, Xuewu Liu, Nitya Turaga, Nathaniel J. Kemnitz, Robert H. Byrne, Jess F. Adkins, Aragonite dissolution kinetics and calcite/aragonite ratios in sinking and suspended particles in the North Pacific, Earth and Planetary Science Letters, Volume 515, 2019, Pages 1-12, ISSN 0012-821X, https://doi.org/10.1016/j.epsl.2019.03.016. (http://www.sciencedirect.com/science/article/pii/S0012821X19301645)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94070
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:22 Mar 2019 23:01
Last Modified:22 Mar 2019 23:01

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