Calving event led to changes in phytoplankton bloom phenology in the Mertz polynya, Antarctica

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Liniger, G, Strutton, PG, Lannuzel, D, Moreau, S
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley-Blackwell Publishing Inc. 2020
• Subjects: calving event; phytoplankton bloom; phenology; Mertz polynya; Antarctica; Mertz Glacier; Mertz Glacier Tongue; Antarc*; Antarctica Journal; Sea ice
• Online Access: https://eprints.utas.edu.au/44047/; https://eprints.utas.edu.au/44047/1/141424%20-%20Calving%20event%20led%20to%20changes%20in%20phytoplankton%20bloom%20phenology_OA.pdf

Polynyas are subject to variability in winds and ocean circulation and are important sites of ecological productivity. In February 2010, the B09B iceberg collided with the Mertz Glacier Tongue (MGT), calving a 78x40 km giant iceberg which modified the icescape and primary productivity of the Mertz Polynya. In this study, we use satellite ocean color and sea‐ice concentration to investigate the variability, trends and drivers of phytoplankton blooms in the Mertz polynya since 1997. During the bloom, over 21 years, we found: (i) a later ice retreat time, (ii) an increase in sea‐ice concentration, (iii) a decrease in open‐water period, (iv) a later bloom start and (v) a decrease in bloom duration. Our results suggest that major post‐calving changes in the physical characteristics of the polynya, mainly its icescape, are the primary drivers of phytoplankton phenology. More specifically, the MGT calving event resulted in significant seasonal and regional changes, with higher eastern chl‐a and mean summer chl‐a post‐calving. While satellite data are useful to study long‐term variability in these inhospitable areas, they only focus on the ocean surface and are obscured by ice and clouds. Additional sub‐surface parameters from seal tags, gliders and moorings in the southernmost polar regions would strengthen our comprehension of phytoplankton and physical changes in ocean dynamics that may have far‐reaching consequences, from global circulation to carbon export.