Physical drivers of biogeochemical variability in the Polar Front Meander
journal contributionposted on 2023-05-21, 08:49 authored by Xiang YangXiang Yang, Peter StruttonPeter Strutton, Ajitha Cyriac, Helen PhillipsHelen Phillips, Pittman, NA, Clara Rodriguez Vives
The Southern Ocean plays a vital role in global ocean circulation, and the Polar Front (PF) is one of its most important physical features. The PF meander south of Tasmania, around 153°E, 55°S, is a very dynamic region which spawns mesoscale eddies, and influences local biogeochemistry and sea-air interaction. By using voyage and ancillary data, we investigated the unusually strong spring bloom in the vicinity of the PF meander in 2018. We infer that the upwelling of deep water at the front and in eddies, brings macronutrients and dissolved iron (dFe) to the surface. Chlorophyll concentration peaked at over 0.6 mg m −3, which is anomalously high for this area. With reduced iron limitation, the physiological characteristics of phytoplankton in the northern, downstream part of the study area also changed. The photochemical efficiency was improved and released this area from its usual high-nutrient low-chlorophyll (HNLC) status. This was mainly indicated by the increase in the dawn Fv/Fm maximum (indictor of photochemical efficiency) from 0.2 to over 0.5. With the biomass increase and healthier community status, we observed consumption of surface dissolved inorganic carbon and increased particulate organic carbon production to about 40 μmol L −1, forming a weak local carbon sink. Through the investigation of multiple years, a weak positive correlation between mixed layer depth shoaling and phytoplankton growth was found, but there was significant interannual variability in this relationship, likely caused by variable eddy conditions and dFe delivery.
Australian Research Council
Publication titleJournal of Geophysical Research: Oceans
Department/SchoolInstitute for Marine and Antarctic Studies
PublisherWiley-Blackwell Publishing Inc.
Place of publicationUnited States
Rights statement© 2022 The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) License, (https://creativecommons.org/licenses/by-nc/4.0/) which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.