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Pan‐Arctic sea ice‐algal chl a biomass and suitable habitat are largely underestimated for multiyear ice |
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| Authors: | Benjamin A Lange Hauke Flores Christine Michel Justin F Beckers Anne Bublitz John Alec Casey Giulia Castellani Ido Hatam Anke Reppchen Svenja A Rudolph Christian Haas |
| Institution: | 1. Alfred‐Wegener‐Institut Helmholtz‐Zentrum für Polar‐ und Meeresforschung, Bremerhaven, Germany;2. Zoological Institute and Zoological Museum, Biocenter Grindel, University of Hamburg, Hamburg, Germany;3. Fisheries and Oceans Canada, Freshwater Institute, Winnipeg, MB, Canada;4. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada;5. Department of Earth and Space Sciences and Engineering, York University, Toronto, ON, Canada;6. Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada;7. Department of Chemical and Biological Engineering, University of British Columbia, Vancouver, BC, Canada;8. Institute of Geography, University of Erlangen‐Nuremberg, Erlangen, Germany |
| Abstract: | There is mounting evidence that multiyear ice (MYI) is a unique component of the Arctic Ocean and may play a more important ecological role than previously assumed. This study improves our understanding of the potential of MYI as a suitable habitat for sea ice algae on a pan‐Arctic scale. We sampled sea ice cores from MYI and first‐year sea ice (FYI) within the Lincoln Sea during four consecutive spring seasons. This included four MYI hummocks with a mean chl a biomass of 2.0 mg/m2, a value significantly higher than FYI and MYI refrozen ponds. Our results support the hypothesis that MYI hummocks can host substantial ice‐algal biomass and represent a reliable ice‐algal habitat due to the (quasi‐) permanent low‐snow surface of these features. We identified an ice‐algal habitat threshold value for calculated light transmittance of 0.014%. Ice classes and coverage of suitable ice‐algal habitat were determined from snow and ice surveys. These ice classes and associated coverage of suitable habitat were applied to pan‐Arctic CryoSat‐2 snow and ice thickness data products. This habitat classification accounted for the variability of the snow and ice properties and showed an areal coverage of suitable ice‐algal habitat within the MYI‐covered region of 0.54 million km2 (8.5% of total ice area). This is 27 times greater than the areal coverage of 0.02 million km2 (0.3% of total ice area) determined using the conventional block‐model classification, which assigns single‐parameter values to each grid cell and does not account for subgrid cell variability. This emphasizes the importance of accounting for variable snow and ice conditions in all sea ice studies. Furthermore, our results indicate the loss of MYI will also mean the loss of reliable ice‐algal habitat during spring when food is sparse and many organisms depend on ice‐algae. |
| Keywords: | CryoSat‐2 habitat classification hockey stick regression light transmittance piecewise regression sea ice algae sea ice bio‐optics the Last Ice Area |