Other data sources - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 200

Figure 6.9. Estimates of sea level by Thompson and Goldstein (2005) with ages calculated
from open-system equations.
6.5.3 Mountain glaciers
Even in the tropics, the highest mountains are capped by ice. The boundary
between elevations where snowfall exceeds melting and elevations where melting
exceeds snowfall corresponds roughly to the position of the mean annual 0 C
isotherm (snowline). Moraines left behind by glaciers that were once more
extensive than they are today are easily identified on all of the world's snow-
capped mountains. Radiocarbon and cosmogenic isotope dating demonstrate
that these moraines formed during the peak of the Last Glacial Maximum
(LGM). Through careful mapping of these features, it has been possible to recon-
struct the elevation of the snowline at the LGM. In most places, lowering was in
the range 830 70m, after correction for the lowered sea level (Broecker, 2002).
Broecker concluded that on high mountains located from 45 Nto45 S the tem-
perature was probably more than 5 C colder than it is today. This change
produced shifts in vegetation zones on mountainsides to lower elevations, as evi-
denced by studies of pollen grains extracted from the sediments of mountainside
lakes and bogs.
Over the last three decades, ice core records have been recovered from 10
high-elevation ice fields, 9 of which are located in lower latitudes. These ice core
histories provide evidence that the growth and decay of the large ice fields in lower
latitudes are often asynchronous, both between hemispheres and with high-latitude
glaciation. Thompson et al. (2005) concluded that variability of precipitation
(rather than temperature change) was the primary driver of glaciation in lower
latitudes.