Sea ice meltwater and Circumpolar Deep Water drive contrasting productivity in three Antarctic polynyas

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Moreau, Sebastien, Lannuzel, Delphine, Janssens, Julie, Arroyo, Mar C., Corkill, Matthew, Cougnon, Eva, Genovese, Cristina, Legresy, Benoit, Lenton, Andrew, Puigcorbé, Viena, Ratnarajah, Lavenia, Rintoul, Stephen R., Roca-Martí, Montserrat, Rosenberg, Mark, Shadwick, Elizabeth H., Silvano, Alessandro, Strutton, Peter G., Tilbrook, Bronte
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Geophysical Union 2019
• Subjects: Polynyas; Primary productivity; Phytoplankton biomass; Ice shelves; Sea ice; Iron; Antarctic; Southern Ocean; The Antarctic; Antarc*; Antarctica; Australian Antarctic Division; Ice Shelf; Ice Shelves
• Online Access: https://hdl.handle.net/1912/24493

Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 124(5), (2019): 2943-2968, doi:10.1029/2019JC015071. In the Southern Ocean, polynyas exhibit enhanced rates of primary productivity and represent large seasonal sinks for atmospheric CO2. Three contrasting east Antarctic polynyas were visited in late December to early January 2017: the Dalton, Mertz, and Ninnis polynyas. In the Mertz and Ninnis polynyas, phytoplankton biomass (average of 322 and 354 mg chlorophyll a (Chl a)/m2, respectively) and net community production (5.3 and 4.6 mol C/m2, respectively) were approximately 3 times those measured in the Dalton polynya (average of 122 mg Chl a/m2 and 1.8 mol C/m2). Phytoplankton communities also differed between the polynyas. Diatoms were thriving in the Mertz and Ninnis polynyas but not in the Dalton polynya, where Phaeocystis antarctica dominated. These strong regional differences were explored using physiological, biological, and physical parameters. The most likely drivers of the observed higher productivity in the Mertz and Ninnis were the relatively shallow inflow of iron‐rich modified Circumpolar Deep Water onto the shelf as well as a very large sea ice meltwater contribution. The productivity contrast between the three polynyas could not be explained by (1) the input of glacial meltwater, (2) the presence of Ice Shelf Water, or (3) stratification of the mixed layer. Our results show that physical drivers regulate the productivity of polynyas, suggesting that the response of biological productivity and carbon export to future change will vary among polynyas. This work was cofunded by the Australian Antarctic Division research projects AAS 4131 and 4291. This project was also supported by the Australian Government Cooperative Research Centres Programme through the Antarctic Climate & Ecosystems (ACE CRC). S. ...