The Cryosphere Discussions www.the-cryosphere-discuss.net 1994-0432 1994-0440 6 1 2012 10.5194/tcd-6-125-2012 http://www.the-cryosphere-discuss.net/6/125/2012/ http://www.the-cryosphere-discuss.net/6/125/2012/tcd-6-125-2012.html http://www.the-cryosphere-discuss.net/6/125/2012/tcd-6-125-2012.pdf 125 158 2012-01-13 Initial sea-ice growth in open water: properties of grease ice and nilas A. K. Naumann ann-kristin.naumann@zmaw.de D. Notz L. Håvik A. Sirevaag Max Planck Institute for Meteorology, Hamburg, Germany Bjerknes Centre for Climate Research, University of Bergen, Bergen, Norway To investigate initial sea-ice growth in open water, we carried out an ice-tank study with three different setups: grease ice grew in experiments with waves and in experiments with a current and wind, while nilas formed in a quiescent experimental setup. In this paper we focus on the differences in bulk salinity, solid fraction and thickness between these two ice types. <br></br> We find that the bulk salinity of the grease-ice layer remains almost constant until the ice starts to consolidate. In contrast, the bulk salinity of nilas is in the first hours of ice formation well described by a linear decrease of 2.1 g kg⁻¹ h⁻¹ independent of air temperature. Such rapid decrease in bulk salinity can be understood qualitatively in the light of a Rayleigh number, the maximum of which is reached while the nilas is still less than 1 cm thick. <br></br> Comparing three different methods to measure solid fraction in grease ice based on (a) salt conservation, (b) mass conservation and (c) energy conservation, we find that the method based on salt conservation does not give reliable results if the salinity of the interstitial water is approximated as being equal to the salinity of the upper water layer. Instead the increase in salinity of the interstitial water during grease-ice formation must be taken into account. We find that the solid fraction of grease ice is relatively constant with values of 0.25, whereas it increases to values as high as 0.5 as soon as the grease ice consolidates at its surface. In contrast, the solid fraction of nilas increases continuously in the first hours of ice formation. <br></br> The ice thickness is found to be twice as large in the first 24 h of ice formation in the setup with a current and wind compared to the other two setups, since the wind keeps parts of the water surface ice free. The development of the ice thickness can be reproduced well with simple, one dimensional models given only the air temperature or the ice surface temperature. Anderson,~D L.: Growth rate of sea ice, J. Glaciol., 3, 1170–1172, 1961. Bromley,~L A., Desaussure,~V A., Clipp,~J C., and Wright,~J S.: Heat capacities of sea water solutions at salinities of 1 to 12 % and temperatures of 2 \degreeC to 80 \degreeC, J. Chem. Eng. Data, 12, 202–206, doi:10.1021/je60033a013, 1967. Chiareli,~A O P. and Worster,~M G.: On measurements and prediction of the solid fraction within mushy layers, J. Cryst. Growth, 125, 487–494, 1992. Cox,~G F N. and Weeks,~W F.: Salinity variations in sea ice, J. Glaciol., 13, 109–120, 1974. Dai,~M., Shen,~H H., Hopkins,~M A., and Ackley,~S F.: Wave rafting and the equilibrium pancake ice cover thickness, J. Geophys. Res., 109, C07023, doi:10.1029/2003JC002192, 2004. De la Rosa,~S. and Maus,~S.: Laboratory study of frazil ice accumulation under wave conditions, The Cryosphere Discuss., 5, 1835–1886, http://dx.doi.org/10.5194/tcd-5-1835-2011doi:10.5194/tcd-5-1835-2011, 2011. %% De la Rosa,~S., Maus,~S., and Kern,~S.: Thermodynamic investigation of an evolving grease to pancake ice field, Ann. Glaciol., 52, 206–214, 2011. Freitag,~J.: Untersuchungen zur Hydrologie des arktischen Meereises – Konsequenzen für den kleinskaligen Stofftransport, Berichte zur Polarforschung 325, Alfred-Wegener Institut für Polar- und Meeresforschung, Bremerhaven, 1999 (in German). Haas,~C., Cottier,~F., Smedsrud,~L H., Thomas,~D., Buschmann,~U., Dethleff,~D., Gerland,~S., Giannelli,~V., Hoelemann,~J., Tison,~J.-L., and Wadhams,~P.: Multidisciplinary ice tank study shedding new light on sea ice growth processes, EOS T. Am. Geophys. Un., 80, 507, doi:10.1029/EO080i043p00507-01, 1999. H\aavik,~L., Sirevaag,~A., Naumann,~A K., and Notz,~D.: Growing ice in a tank: the importance of brine release to the under ice boundary layer, The Cryosphere, in preparation, 2012. Hunke,~E C., Notz,~D., Turner,~A K., and Vancoppenolle,~M.: The multiphase physics of sea ice: a review for model developers, The Cryosphere, 5, 989–1009, http://dx.doi.org/10.5194/tc-5-989-2011doi:10.5194/tc-5-989-2011, 2011. %%ok Lebedev,~V V.: The dependence between growth of ice in Arctic rivers and seas and negative air temperature (in Russian: rost l'da v arkticheskikh rekakh i moriakh v zavisimosti ot otritsatel'nykh temperatur vozdukha), Problemy arktiki, 5, 9–25, 1938. Martin,~S. and Kaufmann,~P.: A field and laboratory study of wave damping by grease ice, J. Glaciol., 27, 283–313, 1981. Maykut,~G A.: Large-scale heat exchange and ice production in the Central Arctic, J. Geophys. Res., 87, 7971–7984, 1982. Maykut,~G A.: The surface heat and mass balance, in: The Geophysics of Sea Ice, edited by: Untersteiner,~N., Plenum Press, New York, 395–463, 1986. Naumann,~A K.: Physikalische Prozesse der Meereisbildung in offenem Wasser, Master's thesis, University of Hamburg, 2011 (in German). Newyear,~K. and Martin,~S.: A comparison of theory and laboratory measurements of wave propagation and attenuation in grease ice, J. Geophys. Res., 102, 25091–25099, 1997. Notz,~D.: Thermodynamic and Fluid-Dynamical Processes in Sea Ice, PH.D. thesis, University of Cambridge, UK, 2005. Notz,~D. and Worster,~M G.: In situ measurements of the evolution of young sea ice, J. Geophys. Res., 113, C03001, doi:10.1029/2007JC004333, 2008. Notz,~D. and Worster,~M G.: Desalination processes of Sea Ice, J. Geophys. Res., 114, C05006, http://dx.doi.org/10.1029/2008JC004885doi:10.1029/2008JC004885, 2009. Omstedt,~A.: Modelling frazil ice and grease ice formation in the upper layer of the ocean, Cold Reg. Sci. Technol., 11, 87–98, 1985. Shen,~H H., Ackley,~S F., and Yuan,~Y.: Limiting diameter of pancake ice, J. Geophys. Res., 109, C12035, doi:10.1029/2003JC0021232004, 2004. Smedsrud,~L H.: Frazil-ice entrainment of sediment: large-tank laboratory experiments, J. Glaciol., 47, 461–471, 2001. Smedsrud,~L H. and Skogseth,~R.: Field measurements of Arctic grease ice properties and processes, Cold Reg. Sci. Technol., 44, 171–183, 2006. Stefan,~J.: Über die Theorie der Eisbildung, insbesondere über die Eisbildung im Polarmeere, Sb. Kais. Akad. Wiss., Wien, Math.-Naturwiss., 98, 965–983, 1889 (in German). Weast,~R C.: Handbook of Chemistry and Physics, 52~edn., Chemical Rubber Co., Cleveland, OH, 1971. Weeks,~W F. and Ackley,~S F.: The growth, structure, and properties of sea ice, in: Geophysics of Sea Ice, edited by: Untersteiner,~N., Plenum Press, New York, 9–164, 1986. Wells,~A J., Wettlaufer,~J S., and Orszag,~S A.: Brine fluxes from growing sea ice, Geophys. Res. Lett., 38, L04501, doi:10.1029/2010GL046288, 2011. Wettlaufer,~J S., Worster,~M G., and Huppert,~H E.: Natural convection during solidification of an alloy from above with application to the evolution of sea ice, J. Fluid Mech., 344, 291–316, 1997. Wilkinson,~J P., DeCarolis,~G., Ehlert,~I., Notz,~D., Evers,~K.-U., Jochmann,~P., Gerland,~S., Nicolaus,~M., Hughes,~N., Kern,~S., de la Rosa,~S., Smedsrud,~L., Sakai,~S., Shen,~H., and Wadhams,~P.: Ice tank experiments highlight changes in sea ice types, EOS T. Am. Geophys. Un., 90, 81–82, 2009. Worster,~M G.: Instabilities of the liquid and mushy regions during solidification of alloys, J. Fluid Mech., 237, 649–669, 1992.