Research
Fluid flow through sea ice
Polar sea ice is an indicator and regulator of climate change. Its presence greatly reduces solar heating of the polar oceans by reflecting incoming radiation, while its thinning and retreat show the effects of global warming. Sea ice is also a primary habitat for algal and bacterial communities, sustaining rich marine food webs. The fluid permeability of sea ice - how easy it is for brine or sea water to flow through the ice - is important to many problems in geophysics and biology, yet has remained poorly understood. We have developed a unified picture of sea ice permeability, combining analytical and numerical modeling, comparisons with laboratory and Arctic field measurements, and X-ray computed tomography of sea ice pore microstructure. Our work prepares the way for more realistic representations of sea ice evolution in climate and biogeochemical models. On the SIPEX expedition in 2007, we made the first measurements of fluid permeability in the Antarctic sea ice pack, and observed tracers moving through blocks of sea ice.
The brine microstructure of sea ice (a) controls its fluid permeabilty, while the permeability constrains processes important to climate such as the drainage of Arctic melt ponds (b) and the formation of snow-ice, as well as processes which are critical to sustaining microbial life, such as nutrient replenishment. We measure the permeability of sea ice by taking a core partially though the ice and then measure how quickly the water level rises in the hole (c). Here the water is about to flood the surface of the ice, a common situtation in the Antarctic. By pouring a tracer like fluorescein over inverted sea ice blocks (d), brine channels and structural transitions in the ice are exposed.
K. M. Golden, Climate change and the mathematics of transport in sea ice, invited article for the Notices of the American Mathematical Society, Volume 56, Number 5, pages 562-584 (including issue cover), May 2009. PDF (Additional References, PDF)
K. M. Golden, H. Eicken, A. L. Heaton, J. Miner, D. Pringle, and J. Zhu, Thermal evolution of permeability and microstructure in sea ice, Geophysical Research Letters, 34, L16501, doi:10.1029/2007GL030447, 6 pages and issue cover, 2007. PDF
K. M. Golden, A. L. Heaton, H. Eicken and V. I. Lytle, Void bounds for fluid transport in sea ice, Mechanics of Materials, 38, pp. 801-817, 2006. PDF
J. Zhu, A. Jabini, K. M. Golden, H. Eicken and M. Morris, A network model for fluid transport in sea ice, Annals of Glaciology, 44, pp. 129-133, 2006. PDF
Remote sensing of sea ice
Monitoring the polar sea ice packs on global or regional scales is an increasingly important problem, typically involving the interaction of an electromagnetic wave with sea ice, a composite of pure ice with brine, air and salt inclusions. In the quasistatic regime where the wavelength is much longer than the composite microstructural scale, the electromagnetic behavior is characterized by the effective complex permittivity. This paramater plays a key role in obtaining sea ice thickness information - important in assessing the impact of climate change - as well as in recovering from electromagnetic data other sea ice properties such as brine porosity. We have been developing mathematical methods to estimate the complex permittivity of sea ice and its dependence on the temperature and salinity of the ice, as well as inverse schemes for recovering microstructural information from permittivity measurements. On the SIPEX expedition in 2007, we measured the electrical properties of Antarctic sea ice, via direct measurements on cores and through a Wenner array, where ice resistivity profiles are reconstructed from surface impedance tomography.
An electromagnetic induction device, called the Worbot, mounted on the port side of the icebreaker Aurora Australis (a), measures sea ice thickness as the ship travels through the pack. Professor Golden sets up a Wenner array of metal probes to measure the electrical resistivity of the sea ice (b).
C. Sampson, K. M. Golden, A. Gully, and A. P. Worby, Surface impedance tomography for Antarctic sea ice, submitted to Deep Sea Research, 2010. PDF
A. Gully, L. G. E. Backstrom, H. Eicken, and K. M. Golden, Complex bounds and microstructural recovery from measurements of sea ice permittivity, Physica B, 394, pp. 357-362, 2007. PDF
K. M. Golden, M. Cheney, K. H. Ding, A. K. Fung, T. C. Grenfell, D. Isaacson, J. A. Kong, S. V. Nghiem, J. Sylvester, and D. P. Winebrenner, Forward electromagnetic scattering models for sea ice, IEEE Transactions on Geoscience and Remote Sensing, 36(5), pp. 1655-1674, 1998. PDF
K. M. Golden, D. Borup, M. Cheney, E. Cherkaeva, M. S. Dawson, K. H. Ding, A. K. Fung, D. Isaacson, S. A. Johnson, A. K. Jordan, J. A. Kong, R. Kwok, S. V. Nghiem, R. G. Onstott, J. Sylvester, D. P. Winebrenner and I. H. H. Zabel, Inverse electromagnetic scattering models for sea ice, IEEE Transactions on Geoscience and Remote Sensing, 36(5), pp. 1675-1704, 1998. PDF
Statistical mechanics of electrorheological fluids
When a sufficiently strong electric field is applied to a suspension of plastic spheres in oil, they quickly form chains (a) and then columns where the spheres are arranged in periodic lattice configurations. The suspension undergoes a rapid transition from fluid to solid-like behavior. When the spheres are metal, as in (b), they form connected clusters with fractal structure (W. Wen and K. Lu, Phys. Fluids Lett. 1996). These electrorheolgical (ER) fluids, and magnetic analogs called magnetorheolgical (MR) fluids, are being used in the car industry and in prosthetics. We're using ideas from statistical mechanics in the physics of phase transitions to study ER fluids.
K. M. Golden, Statistical mechanics of conducting phase transitions, Journal of Mathematical Physics, 36, pp. 5627-5642, 1995. PDF
K. M. Golden, Critical behavior of transport in lattice and continuum percolation models, Physical Review Letters, 78, pp. 3935-3938, 1997. PDF
Current Postdoctoral Researchers
Joyce Lin (VIGRE Research Assistant Professor) - Numerical models of sea ice and ER fluid microstructures; experiments on sea ice EM properties and ER fluids
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