Premium
How Should Snowball Earth Deglaciation Start
Author(s) -
Wu Jiacheng,
Liu Yonggang,
Zhao Zhouqiao
Publication year - 2021
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2020jd033833
Subject(s) - deglaciation , snowball earth , equator , geology , glacier , earth system science , climatology , latitude , glacial period , physical geography , oceanography , geodesy , geomorphology , geography
The 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. Deglaciation of a snowball Earth will start when the annual mean equatorial surface temperature is only −7.7°C rather than 0°C. At this point, seasonal melt ponds start to appear in the mid‐latitude region. Its positive feedback induces the appearance of perennial melt ponds within the equatorial region and can increase the annual mean temperature there to 6.1°C in less than 10 years. Thus, our results indicate that the threshold CO 2 required to deglaciate a snowball Earth will be greatly overestimated (by a factor of ∼4 for the model we use) if the annual mean surface temperature reaching 0°C is used as the criteria. The results also demonstrate unambiguously that the deglaciation of snowball Earth should start from the equator. We then speculate on what will happen to the tropical sea glacier after the surface melting starts.