Synchronicity between ice retreat and phytoplankton bloom in circum-Antarctic polynyas
Résumé
Phytoplankton in Antarctic coastal polynyas has a temporally short yet spatially variant growth
window constrained by ice cover and day length. Using 18-year satellite measurements (1997–2015) of sea
ice and chlorophyll concentrations, we assessed the synchronicity between the spring phytoplankton bloom
and light availability, taking into account the ice cover and the incident solar irradiance, for 50 circum-Antarctic
coastal polynyas. The synchronicity was strong (i.e., earlier ice-adjusted light onset leads to earlier bloom and
vice versa) in most of the western Antarctic polynyas but weak in a majority of the eastern Antarctic polynyas.
The west-east asymmetry is related to sea ice production rate: the formation ofmany eastern Antarctic polynyas
is associated with strong katabatic wind and high sea ice production rate, leading to stronger water column
mixing that could damp phytoplankton blooms and weaken the synchronicity.