Modeling ice algal growth and decline in a seasonally ice‐covered region of the Arctic (Resolute Passage, Canadian Archipelago)

Abstract

[1] We have developed a coupled snow-ice-ice algae model to investigate the importance of different ice algal growth limitation terms, as well as different loss terms, in regulating the ice algal biomass accumulation at the bottom of landfast ice in the Canadian Archipelago. The model results are compared with data collected from May to July 2002 at a station near Resolute in Barrow Strait. Our results show that ice algae are light limited at the beginning of the bloom, then fluctuate between light and nutrient limitation, finally remaining nutrient limited toward the end of the bloom. The fortnightly tide modulates the ice algal biomass through the supply of nutrient to the ice algal layer but mainly through modulation of the bottom ice melt rate. We also demonstrate that the bottom ice melt rate regulates the maximum biomass attained in the region and that a rapid increase in ice temperature can lead to a significant decline in ice algal biomass. The eventual termination of the bloom is triggered by melting of the snow cover and results from (1) increased ice algal losses due to high bottom ice melt rate and (2) decreased ice algal growth due to nutrient limitation caused by the formation of a meltwater lens below the ice. Finally, our results show that the snow cover controls the length of the bloom, such that earlier snowmelt that is expected to accompany climate warming may lead to a reduction in ice algal production.

Role of sea ice in global biogeochemical cycles: emerging views and challenges

“…There are instances of mono-band [e.g., Lavoie et al, 2005] or multi-band schemes [Arrigo et al, 1993] in the literature, but all suffer from uncertainties, the largest being associated with the optical properties of snow [Pogson et al, 2011]. Furthermore, the required components for proper eco-dynamics are not known either.…”

“…Ice algae are typically shade adapted and can thrive at very low irradiances. Increasing light levels in late winter trigger the onset of ice-algal blooms [Lavoie et al, 2005;Meiners et al, 2012]. The decline of Arctic ice algal blooms depends on a variety of factors including nutrient limitation by nitrogen [Różańska et al, 2009] and silicic acid [Lavoie et al, 2005], self-shading , as well as temperature and brine salinity stress [Arrigo and Sullivan, 1992].…”

“…Hence, despite significant light levels, various chemical elements have been reported to limit ice algal production in Arctic sea ice in late spring / early summer: N in the Chukchi and Beaufort Seas, in June [Gradinger, 2009], and Si in the Canadian Arctic Archipelago in June [Lavoie et al, 2005]. Nutrient limitation of Antarctic sea ice algae has also been reported for both surface and bottom communities [e.g., Kristiansen et al, 1998;McMinn et al, 1999] but seems less widespread than in the Arctic, although it is not clear whether this is due to a lack of summer observations or to undocumented summer nutrient supply mechanisms.…”

“…First, the nutrient fluxes are based on simple formulations and do not account for brine transport. Consequently, the location of ice algal growth has to be prescribed, either at the base [e.g., Lavoie et al, 2005] or at the top of the ice cover [e.g., Arrigo et al, 1997;Saenz and Arrigo, 2012], and therefore the models are not general enough to handle both Arctic and Antarctic situations. Vancoppenolle et al [2010] and Jeffery et al [2011], have developed schemes to couple dissolved tracers to brine dynamics, and applied their model to successful simulations of silicate concentrations and salinity, respectively, but their approach has not yet been coupled to formulations of ecodynamics.…”

“…These models (see Figure 4c) can be viewed as testing tools focussing on undeformed sea ice and can be used in a single location but not globally. Originally inspired from ocean biogeochemistry models, they are based on simple N-P formulations [see, e.g., Sarmiento and Gruber, 2006] and include (i) a single plankton group (diatoms) located at a prescribed depth in the ice (surface or bottom), (ii) one or several limiting nutrients, assimilated by ice algae with prescribed elemental (Redfield) ratios, and simple physics [Arrigo et al, 1993;Lavoie et al, 2005;Jin et al, 2006;Saenz and Arrigo, 2012]. Those 1D models reasonably well simulate Arctic and the Antarctic sea ice algal developments over a few months.…”