• Aagaard, K., and P. Greisman, 1975: Towards new mass and heat budgets for the Arctic Ocean. J. Geophys. Res., 80 , 38213827.

  • Bryden, H. L., H. R. Longworth, and S. A. Cunningham, 2005: Overturning circulation in the North Atlantic. Nature, 438 , 655657.

  • Carmack, E., and Coauthors, 1997: Changes in temperature and tracer distributions within the Arctic Ocean: Results from the Arctic Ocean section. Deep-Sea Res., 44 , 14871502.

    • Search Google Scholar
    • Export Citation
  • Cullather, R. I., and L-B. Tremblay, 2008: Analysis of Arctic sea ice anomalies in a coupled model control simulation. Arctic Sea Ice Decline: Observations, Projections, Mechanisms and Implications, Geophys. Monogr., Vol. 180, Amer. Geophys. Union, 187–211.

    • Search Google Scholar
    • Export Citation
  • Deser, C., and H. Teng, 2008: Recent trends in Arctic sea ice and the evolving role of atmospheric circulation forcing, 1979-2007. Arctic Sea Ice Decline: Observations, Projections, Mechanisms and Implications, Geophys. Monogr., Vol. 180, Amer. Geophys. Union, 7–26.

    • Search Google Scholar
    • Export Citation
  • DeWeaver, E. T., C. M. Bitz, and L-B. Tremblay, Eds.,. 2008: Arctic Sea Ice Decline: Observations, Projections, Mechanisms and Implications. Geophys. Monogr., Vol. 180, Amer. Geophys. Union, 269 pp.

    • Search Google Scholar
    • Export Citation
  • Kelley, D. E., 1984: Effective diffusivities within oceanic thermohaline staircases. J. Geophys. Res., 89 , 1048410488.

  • Kelley, D. E., H. J. S. Fernando, A. E. Gargett, J. Tanny, and E. Ozsoy, 2003: The diffusive regime of double-diffusive convection. Prog. Oceanogr., 56 , 461481.

    • Search Google Scholar
    • Export Citation
  • Neal, V. T., S. Neshyba, and W. Denner, 1969: Thermal stratification in the Arctic Ocean. Science, 166 , 373374.

  • Padman, L., and T. M. Dillon, 1987: Vertical fluxes through the Beaufort Sea thermohaline staircase. J. Geophys. Res., 92 , 1079910806.

    • Search Google Scholar
    • Export Citation
  • Perovich, D. K., and B. Elder, 2002: Estimates of ocean heat flux at SHEBA. Geophys. Res. Lett., 29 , 1344. doi:10.1029/2001GL014171.

  • Perovich, D. K., T. C. Grenfell, J. A. Richter-Menge, B. Light, W. B. Tucker III, and H. Eicken, 2003: Thinner and thinner: Sea ice mass balance measurements during SHEBA. J. Geophys. Res., 108 , 8050. doi:10.1029/2001JC001079.

    • Search Google Scholar
    • Export Citation
  • Rothrock, D. A., Y. Yu, and G. A. Maykut, 1999: Thinning of the Arctic sea ice cover. Geophys. Res. Lett., 26 , 34693472.

  • Rothrock, D. A., J. Zhang, and Y. Yu, 2003: The Arctic ice thickness anomaly of the 1990s: A consistent view from observations and models. J. Geophys. Res., 108 , 3083. doi:10.1029/2001JC001208.

    • Search Google Scholar
    • Export Citation
  • Stocker, T. F., and D. G. Wright, 1991: Rapid transitions of the ocean’s deep circulation induced by changes in surface water fluxes. Nature, 351 , 729732.

    • Search Google Scholar
    • Export Citation
  • Turner, J. S., 1965: The coupled turbulent transport of salt and heat across a sharp density interface. Int. J. Heat and Mass Trans., 8 , 759767.

    • Search Google Scholar
    • Export Citation
  • Turner, J. S., 2005: The melting of ice in the Arctic Ocean: Double-diffusive transport of heat from below. Extended Abstracts, 16th National Congress, Canberra, Australia, Australian Institute of Physics, 85.

    • Search Google Scholar
    • Export Citation
  • Turner, J. S., and G. Veronis, 2000: Laboratory studies of double-diffusive sources in closed regions. J. Fluid Mech., 405 , 269304.

  • Turner, J. S., and G. Veronis, 2004: The influence of double-diffusive processes on the melting of ice in the Arctic Ocean: Laboratory analogue experiments and their interpretation. J. Mar. Syst., 45 , 2137.

    • Search Google Scholar
    • Export Citation
  • Wadhams, P., and N. R. Davis, 2000: Further evidence of ice thinning in the Arctic Ocean. Geophys. Res. Lett., 27 , 39733975.

  • Wells, M. G., and J. S. Wettlaufer, 2007: The long-term circulation driven by density currents in a two-layer stratified basin. J. Fluid Mech., 572 , 3758.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 287 174 0
PDF Downloads 243 143 0

The Melting of Ice in the Arctic Ocean: The Influence of Double-Diffusive Transport of Heat from Below

View More View Less
  • 1 Research School of Earth Sciences, Australian National University, Canberra, Australian Capital Territory, Australia
Restricted access

Abstract

This investigation was originally prompted by two oceanographic observations: an increased rate of melting of sea ice in the Arctic Ocean, and the advance of an anomalously warm tongue of Atlantic water intruding across the Arctic below the halocline over the past few decades. A series of laboratory model experiments has previously been carried out to explore the possibility that the extra heating at depth could be responsible for the enhanced melting rate. These experiments have demonstrated that a one-dimensional heat flux from below through a series of double-diffusive layers can in principle lead to faster melting of floating ice. However, it is now essential to test these ideas quantitatively under ocean conditions and to compare the results with other possible mechanisms of melting.

A simple calculation shows that there is enough heat in the intruding Atlantic water to melt all the ice in the Arctic in a few years if all the heat could be brought to the surface in this time. The vertical double-diffusive transport of heat is slower than this, but it is large enough to make a substantial contribution to the increased rate of melting over the last three or four decades. Another proposed mechanism for melting is the solar input to the surface mixed layer from the atmosphere. In particular years when detailed measurements and calculations have been made, this atmospheric input can explain both the seasonal cyclic behavior of ice and the increased melting rate. Given the large heat content in the intruding Atlantic layer, however, it seems worth exploring further other advective two-dimensional mechanisms that could transport this heat upward more rapidly than the purely vertical double-diffusive convection. For example, dense salty water produced by freezing on the shelves around the Arctic Basin could flow down the slope and penetrate through the halocline, thus mixing with the warm water and bringing it to the surface.

Corresponding author address: J. S. Turner, Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia. Email: stewart.turner@anu.edu.au

Abstract

This investigation was originally prompted by two oceanographic observations: an increased rate of melting of sea ice in the Arctic Ocean, and the advance of an anomalously warm tongue of Atlantic water intruding across the Arctic below the halocline over the past few decades. A series of laboratory model experiments has previously been carried out to explore the possibility that the extra heating at depth could be responsible for the enhanced melting rate. These experiments have demonstrated that a one-dimensional heat flux from below through a series of double-diffusive layers can in principle lead to faster melting of floating ice. However, it is now essential to test these ideas quantitatively under ocean conditions and to compare the results with other possible mechanisms of melting.

A simple calculation shows that there is enough heat in the intruding Atlantic water to melt all the ice in the Arctic in a few years if all the heat could be brought to the surface in this time. The vertical double-diffusive transport of heat is slower than this, but it is large enough to make a substantial contribution to the increased rate of melting over the last three or four decades. Another proposed mechanism for melting is the solar input to the surface mixed layer from the atmosphere. In particular years when detailed measurements and calculations have been made, this atmospheric input can explain both the seasonal cyclic behavior of ice and the increased melting rate. Given the large heat content in the intruding Atlantic layer, however, it seems worth exploring further other advective two-dimensional mechanisms that could transport this heat upward more rapidly than the purely vertical double-diffusive convection. For example, dense salty water produced by freezing on the shelves around the Arctic Basin could flow down the slope and penetrate through the halocline, thus mixing with the warm water and bringing it to the surface.

Corresponding author address: J. S. Turner, Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia. Email: stewart.turner@anu.edu.au

Save