BFM-SI: a new implementation of the Biogeochemical Flux Model in sea ice

CMCC Research Papers 03/2010; DOI: 10.2139/ssrn.1633366
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    ABSTRACT: In the last decades the scientific community has been making lot of efforts to understand the physics of sea ice. We currently have a good knowledge of the sea ice dynamics and thermodynamics and of their temporal and spatial variability. Sea ice biogeochemistry is instead largely unknown. There are only sparse localized observations and little knowledge of the functioning of sea ice biogeochemistry at larger scales. Modelling becomes then a necessary tool to qualify and quantify the role of sea ice biogeochemistry in the ocean dynamics. We used a different approach with respect to the previous attempts of modelling the sea ice biogeochemistry and in particular of its primary production. The central concept is the definition of the Biologically-Active-Layer (BAL), which is the time-varying fraction of sea ice that is continuously connected to the ocean via brines pockets and channels. A 1-D Enhanced Sea Ice halo-thermodynamic Model (ESIM2) is able to simulate the key physical properties of the BAL (thickness, temperature, brines salinity and volume, sea ice bulk salinity and irradiance), which are passed to the new implementation of the Biogeochemical Flux Model in sea ice (BFM-SI). The new BFM-SI uses those information to simulate the physiological and ecological response of the biological community in sea ice. The new model is also coupled to the pelagic BFM through the exchange of organic and inorganic matter at the boundaries between the two systems . This is done by computing the entrapment of matter and gases when sea ice grows and release to the ocean when sea ice melts and it is thus totally mass-conserving. The implementation of the BFM-SI model and coupling structure in General Circulation Models will add a new component to GCMs (and in general to Earth System Models), which will be finally able to estimate globally the role and importance of sea ice biogeochemistry in the global carbon cycle.
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    ABSTRACT: Sea ice is a fundamental component of the climate system and plays a key role in polar trophic food webs. Nonetheless sea ice biogeochemical dynamics at large temporal and spatial scales are still rarely described. Numerical models may potentially contribute integrating among sparse observations, but available models of sea ice biogeochemistry are still scarce, whether their relevance for properly describing the current and future state of the polar oceans has been recently addressed. A general methodology to develop a sea ice biogeochemical model is presented, deriving it from an existing validated model application by extension of generic pelagic biogeochemistry model parameterizations. The described methodology is flexible and considers different levels of ecosystem complexity and vertical representation, while adopting a strategy of coupling that ensures mass conservation. We show how to apply this methodology step by step by building an intermediate complexity model from a published realistic application and applying it to analyze theoretically a typical season of first-year sea ice in the Arctic, the one currently needing the most urgent understanding. The aim is to (1) introduce sea ice biogeochemistry and address its relevance to ocean modelers of polar regions, supporting them in adding a new sea ice component to their modelling framework for a more adequate representation of the sea ice-covered ocean ecosystem as a whole, and (2) extend our knowledge on the relevant controlling factors of sea ice algal production, showing that beyond the light and nutrient availability, the duration of the sea ice season may play a key-role shaping the algal production during the on going and upcoming projected changes.
    PLoS ONE 02/2014; 9(2):e89217. DOI:10.1371/journal.pone.0089217 · 3.23 Impact Factor

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Jun 1, 2014