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\begin{document}

\title{AN ESTIMATE OF THE VOLUME OF PHANEROZOIC ICE}



\author[1]{Christopher Scotese}%
\affil[1]{Northwestern University}%


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  \date{June 14, 2024}


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\begin{abstract}
We live in an ``Ice House'' world that has extensive ice cover at both
poles. However, it has not always been this way. During the last 540
million years there have been only 4 other time intervals characterized
by extensive polar ice caps (latest Ordovician, latest Devonian,
Permo-Carboniferous, and late Cenozoic). The combined duration of these
frigid intervals was approximately 160 million years, or
\textasciitilde{}30\% of Phanerozoic history. During the remaining 380
million years the Earth lacked permanent polar ice caps, though some
winter snow and ice may have accumulated at high latitudes during cool,
greenhouse intervals (Silurian-early Devonian, late Jurassic -- early
Cretaceous). The modern ice house world is probably the most severe of
all ice house worlds because it is the only time in Earth history when
the North and South polar regions were concurrently glaciated. Using the
compilation of lithologic indicators of glacial conditions (tillites,
dropstone, \& glendonites) compiled by Boucot et al. (2013), I have
mapped the areal extent of polar ice caps (millions of km2) for the time
periods when ice house conditions prevailed. Using a simple algorithm
that estimates the thickness of the ice based on the total area of the
ice cap, I have calculated the corresponding volume of continental ice
(millions of km3) for each of these time intervals. Converting solid ice
to liquid water, the equivalent volume of evaporated ocean water was
calculated. Expressed as a percentage of the present-day volume of ocean
water (1.35 billion km3), I estimated the amount of water removed from
the oceans during each of these ice house intervals. Preliminary
results, indicate that the five largest ice volume events were the
Hirnantian (444.5 Ma) -- 2\%, Modern World -- 2\%, Pliocene (3 Ma) --
2\%, early Permian (280 Ma) -- 1.5\%, and late Miocene (10-15 Ma) --
1.4\%. Since the water removed from the oceans by evaporation is
preferential enriched in 16O, it is possible to calculate the resulting
\selectlanguage{greek}δ\selectlanguage{english}18O of the remaining oceanic reservoir. These calculations may be
useful when estimating paleotemperatures from the \selectlanguage{greek}δ\selectlanguage{english}18O record of fossil
organisms.%
\end{abstract}%



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