Synchronicity between ice retreat and phytoplankton bloom in circum‐Antarctic polynyas

Abstract

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 of many 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.

The frequency and extent of sub-ice phytoplankton blooms in the Arctic Ocean

“…To restrict our interest to only Arctic sub-ice blooms, we excluded grid cells with less than 80% ice concentration, typically defined as the “marginal ice zone,” from the calculation (in contrast to J16, which included these regions when computing under ice primary production). As mentioned above, the marginal ice zone was previously considered the only site where sub-ice phytoplankton blooms were possible ( 38 , 39 ), but the focus of this study is on blooms underneath sea ice, where open-ocean or marginal ice zone processes, like wind-driven vertical mixing, are less important. We additionally exclude Baffin Bay from the study region to focus on the Arctic Basin alone.…”

Mapping and assessing variability in the Antarctic marginal ice zone, pack ice and coastal polynyas in two sea ice algorithms with implications on breeding success of snow petrels

“…While it is difficult to measure the fine-scale location of a polynya at 25 km spatial resolution, the lower sea ice concentrations provide an indication of some open water near the coast, which for seabirds provides a source of open water for foraging. We have previously tested mapping polynyas using a SIC threshold of 0.75 and 0.85 for the NASA Team and Bootstrap algorithms, respectively, and found that these thresholds provided consistent polynya areas between the two algorithms and matched other estimates of the spatial distribution of polynyas (see Li et al, 2016). However, for this study we chose just one threshold, a compromise between the two algorithms, so that we can better determine the sensitivity of using the same threshold on polynya area and timing of formation.…”

“…Both polynyas and the MIZ are biologically important regions of the sea ice cover that have implications for the entire trophic web, from primary productivity (Yun et al, 2015) to top predator species, such as seabirds. Near the ice edge and in the MIZ, the stable upper layer of the water column is optimal for phytoplankton production (e.g., Park et al, 1999).…”

Circumpolar analysis of the Adélie Penguin reveals the importance of environmental variability in phenological mismatch

“…Previous work has shown this metric to be highly correlated with phytoplankton‐bloom phenology, as deduced from ocean color, near Penguin breeding colonies (Li et al. ). We calculated bloom onset using a 250 km radius, which incorporates the size of most coastal polynyas (Arrigo and van Dijken , Arrigo et al.…”

“…This is calculated by taking the Julian day in which a particular light threshold is reached within a 250 km radius of the colony of interest, and applying a correction for light blocked by local sea ice (see Li et al. ). Previous work has shown this metric to be highly correlated with phytoplankton‐bloom phenology, as deduced from ocean color, near Penguin breeding colonies (Li et al.…”