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Controls on the seasonal variability of calcium carbonate saturation states in the Atlantic gateway to the Arctic Ocean

Controls on the seasonal variability of calcium carbonate saturation states in the Atlantic gateway to the Arctic Ocean
Controls on the seasonal variability of calcium carbonate saturation states in the Atlantic gateway to the Arctic Ocean
In addition to ocean acidification due to a gradual anthropogenic CO2 uptake, strong seasonal variations in the carbonate system occur in the Arctic Ocean as a result of physical and biological processes. Understanding this seasonal variability is critical for predicting the onset of calcium carbonate mineral (?) undersaturation with increasing atmospheric CO2 concentrations. However, these variations are currently poorly understood because of a lack of winter data due to the challenging field conditions in this season. Here we report observations over an annual cycle of the carbonate system of surface waters in the Atlantic gateway to the Arctic Ocean, covering the region between Svalbard and mainland Norway. Dissolved inorganic carbon (DIC) concentrations ranged from 2137–2148 ?mol kg? 1 in winter to 1986–2094 ?mol kg? 1 in summer, and total alkalinity (TA) concentrations between 2312–2341 ?mol kg? 1 in winter and 2199–2317 ?mol kg? 1 in summer. This resulted in an increase in TA:DIC ratios from 1.077–1.090 in winter to 1.106–1.112 in summer, mainly due to the biological uptake of CO2 during spring and summer. Similarly, a significant seasonal variability was observed in ? (0.4–0.9), with lowest saturation states in winter (?aragonite ~ 1.8–2.1) and highest in spring and summer (?aragonite ? 2.4). Analysis of the biogeochemical and physical processes that impact aragonite saturation states (?ar) showed biological production to be the most important factor driving seasonal variability in ?ar in this area, accounting for 45–70% of the difference between winter and summer values. Future changes in these processes may alter the seasonal cycle of the carbonate system in both amplitude and timing, and further observations are required to determine the progress of ocean acidification in the Atlantic waters entering the Arctic Ocean.
CO2 dynamics, Carbonate system, Ocean acidification, Saturation states, Carbon cycle, Arctic Ocean
0304-4203
1-9
Tynan, Eithne
dfed4bbd-ea2a-4ff9-81f5-de2af563943b
Tyrrell, Toby
6808411d-c9cf-47a3-88b6-c7c294f2d114
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Tynan, Eithne
dfed4bbd-ea2a-4ff9-81f5-de2af563943b
Tyrrell, Toby
6808411d-c9cf-47a3-88b6-c7c294f2d114
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9

Tynan, Eithne, Tyrrell, Toby and Achterberg, Eric P. (2014) Controls on the seasonal variability of calcium carbonate saturation states in the Atlantic gateway to the Arctic Ocean. Marine Chemistry, 158, 1-9. (doi:10.1016/j.marchem.2013.10.010).

Record type: Article

Abstract

In addition to ocean acidification due to a gradual anthropogenic CO2 uptake, strong seasonal variations in the carbonate system occur in the Arctic Ocean as a result of physical and biological processes. Understanding this seasonal variability is critical for predicting the onset of calcium carbonate mineral (?) undersaturation with increasing atmospheric CO2 concentrations. However, these variations are currently poorly understood because of a lack of winter data due to the challenging field conditions in this season. Here we report observations over an annual cycle of the carbonate system of surface waters in the Atlantic gateway to the Arctic Ocean, covering the region between Svalbard and mainland Norway. Dissolved inorganic carbon (DIC) concentrations ranged from 2137–2148 ?mol kg? 1 in winter to 1986–2094 ?mol kg? 1 in summer, and total alkalinity (TA) concentrations between 2312–2341 ?mol kg? 1 in winter and 2199–2317 ?mol kg? 1 in summer. This resulted in an increase in TA:DIC ratios from 1.077–1.090 in winter to 1.106–1.112 in summer, mainly due to the biological uptake of CO2 during spring and summer. Similarly, a significant seasonal variability was observed in ? (0.4–0.9), with lowest saturation states in winter (?aragonite ~ 1.8–2.1) and highest in spring and summer (?aragonite ? 2.4). Analysis of the biogeochemical and physical processes that impact aragonite saturation states (?ar) showed biological production to be the most important factor driving seasonal variability in ?ar in this area, accounting for 45–70% of the difference between winter and summer values. Future changes in these processes may alter the seasonal cycle of the carbonate system in both amplitude and timing, and further observations are required to determine the progress of ocean acidification in the Atlantic waters entering the Arctic Ocean.

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More information

Published date: 20 January 2014
Keywords: CO2 dynamics, Carbonate system, Ocean acidification, Saturation states, Carbon cycle, Arctic Ocean
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 361844
URI: http://eprints.soton.ac.uk/id/eprint/361844
ISSN: 0304-4203
PURE UUID: cf26140c-e60e-42d7-a41f-cc3a24816473
ORCID for Toby Tyrrell: ORCID iD orcid.org/0000-0002-1002-1716

Catalogue record

Date deposited: 04 Feb 2014 12:02
Last modified: 31 Jul 2019 00:50

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