Air-Sea CO2 Exchange and Carbon Dynamics in Foxe Basin: Findings from a 2023 Oceanographic Survey

The ocean plays an important role in climate by removing large amounts of carbon dioxide (CO2) from the atmosphere through air-sea gas exchange. This process is particularly important in polar oceans, where sea-ice formation releases brine to the water column below and can create dense waters that sink and sequester dissolved carbon into deep waters. Foxe Basin, an inland sea north of Hudson Bay between Baffin Island and Melville Peninsula, is an ideal location to study this process as it is one of the few known places in Canada where sea-ice-driven deep water formation occurs consistently. A synoptic survey took place in Foxe Basin aboard the research icebreaker CCGS Amundsen in October 2023. Findings indicate that Foxe Basin was a weak sink for atmospheric CO2 during fall with a mean pCO2 of 396 ± 19 µatm and air-sea CO2 flux (FCO2) of -1.9 ± 2.1 mmol m⁻² day⁻¹. High pCO2 and positive FCO2 were associated with water column mixing and upwelling along the shelf break and Foxe Peninsula, while high pCO2 near Hall Beach reflected meteoric water input. Deep water bearing the signature of sea-ice brine formation (high salinity, low temperatures) and enriched in dissolved inorganic carbon (DIC) and total alkalinity (TA) was observed in Foxe Channel. A carbon budget attributed the 160 µmol kg⁻¹ enrichment in DIC between the surface and deep water to brine rejection (72%), respiration (24%), and gas exchange (4%). TA:DIC ratios showed no evidence that ikaite retention in sea ice affected bottom water carbonate chemistry. This thesis provides some of the first estimates of CO2 concentrations and carbon export in Foxe Basin, offering exciting insights into Arctic carbon cycling. This work highlights that sea-ice processes in Foxe Basin are particularly important for carbon export to deep water, making Foxe Basin an ideal location to study the role of sea ice in carbon export. These findings establish a foundation for future research necessary to achieve a comprehensive understanding of the basin's carbon dynamics.

Name thesis:degree_name

Master of Science (MSc)

Discipline thesis:degree_discipline

Geography

Grantor dc:publisher.institution

Graduate Studies

Year dc:date.issued

2026

Author dc:creator

• Purdon, Cassandra Charlotte

Advisor dc:contributor.advisor

• Else, Brent

Committee members dc:contributor.committeemember

• Tutolo, Benjamin
• Yackel, John

• Biogeochemistry
• Carbon dynamics
• Air-sea CO2 exchange
• Arctic
• Foxe Basin

Statement dc:rights

• University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.

Language dc:language.iso

en

DOI

https://dx.doi.org/10.11575/PRISM/51005

OAI identifier oai:identifier

oai:ucalgary.scholaris.ca:1880/123940