Abstract
Formation of melt ponds is pervasive on sea ice and ice shelves prior to
their disintegration. Such process should be critical for the
deglaciation of a snowball Earth but has never been considered in
previous studies. Here we develop a module to explicitly track the
initiation, growth and refreezing of melt ponds on ice. Incorporation of
the module into a climate model indicates that it provides a strong
positive feedback to the climate, and previous studies seriously
overestimated the threshold CO2 at which a snowball
Earth deglaciates. At CO2 level of 0.1 bar and without
the melt pond effect, the annual mean equatorial surface temperature is
only -7.7 °C, far from deglaciating. However, this temperature increases
to 6.1 °C in a few tens of years once melt pond effect is turned on. The
results also demonstrate unambiguously that the deglaciation of snowball
Earth should start from the equator, although seasonal melt ponds may
appear first in the subtropical regions.