The first major consolidated work to reconstruct the ice
sheets at the end of the last glaciation was published by
Denton and Hughes (1981). Their method of reconstruction
involved the assumption that the profile of the ice sheets was
parabolic (a hypothesis which is more or less valid for current
ice sheets but which is based on the assumption of a stationary state) and the use of geomorphological data to constrain the extent. Since moraine dating was not as accurate at
the time as it is now, in many areas it was assumed that the
moraines were from the Last Glacial Maximum even though
some had been formed during previous glaciations. Their
reconstructions (even the ‘minimal’ one) are therefore considerably overestimated compared to the values acknowledged today. These reconstructions were also in contradiction
with the global ice volume estimates from other sources
(marine sediments, Mix and Ruddiman 1984).
Afterwards, understanding quickly evolved into a more
dynamic view of ice sheets. For example, Boulton and Clark
(1990) proposed a history of the Laurentide and in particular
the migration and junction of the various domes (we will
return to this in the section on the Laurentide). As for
Fennoscandia, Lambeck et al. (2006) present its evolution
throughout the last glaciation and Hughes et al. (2016)
propose a chronology of the deglaciation. This type of
overview often requires input from several groups of
researchers and large-scale projects were established to
estimate the extent and dynamics of ancient ice sheets
(EPILOG 2002; QUEEN, Svendsen et al. 2004).
Fig. 24.6 The Eurasian ice sheet at various times in the past. Each
map, centered on the Urals, represents the same region of northern
Eurasia but at different times. The extent of the cap was determined
from geomorphological data. During the Saalien (the penultimate
glacial maximum, age >140 ka), the ice sheet extended particularly far
towards the south reaching almost its maximum size during the
Quaternary. The presence of lobes (the Dnieper during the Saalien and
the Don for the maximum expansion) should be noted. These lobes may
be the result of specific events called surges, during which the flow of
glaciers or ice streams is particularly rapid. A tongue of ice then forms
before disappearing, because its low altitude makes it prone to ablation.
It can be seen that at the beginning of the Ice Age (90 ka), the ice sheet
is prominent in the East but limited towards the West over Scandinavia.
During the Last Glacial Maximum, the situation is reversed. Note that
between each period represented here, there were periods when it was
relatively clear of ice and snow, with the disappearance of the ice sheet
located over the Sea of Barents and the separation into two sheets.
Adapted from Svendsen et al. (2004)
24 The Cryosphere and Sea Level
311
sheets at the end of the last glaciation was published by
Denton and Hughes (1981). Their method of reconstruction
involved the assumption that the profile of the ice sheets was
parabolic (a hypothesis which is more or less valid for current
ice sheets but which is based on the assumption of a stationary state) and the use of geomorphological data to constrain the extent. Since moraine dating was not as accurate at
the time as it is now, in many areas it was assumed that the
moraines were from the Last Glacial Maximum even though
some had been formed during previous glaciations. Their
reconstructions (even the ‘minimal’ one) are therefore considerably overestimated compared to the values acknowledged today. These reconstructions were also in contradiction
with the global ice volume estimates from other sources
(marine sediments, Mix and Ruddiman 1984).
Afterwards, understanding quickly evolved into a more
dynamic view of ice sheets. For example, Boulton and Clark
(1990) proposed a history of the Laurentide and in particular
the migration and junction of the various domes (we will
return to this in the section on the Laurentide). As for
Fennoscandia, Lambeck et al. (2006) present its evolution
throughout the last glaciation and Hughes et al. (2016)
propose a chronology of the deglaciation. This type of
overview often requires input from several groups of
researchers and large-scale projects were established to
estimate the extent and dynamics of ancient ice sheets
(EPILOG 2002; QUEEN, Svendsen et al. 2004).
Fig. 24.6 The Eurasian ice sheet at various times in the past. Each
map, centered on the Urals, represents the same region of northern
Eurasia but at different times. The extent of the cap was determined
from geomorphological data. During the Saalien (the penultimate
glacial maximum, age >140 ka), the ice sheet extended particularly far
towards the south reaching almost its maximum size during the
Quaternary. The presence of lobes (the Dnieper during the Saalien and
the Don for the maximum expansion) should be noted. These lobes may
be the result of specific events called surges, during which the flow of
glaciers or ice streams is particularly rapid. A tongue of ice then forms
before disappearing, because its low altitude makes it prone to ablation.
It can be seen that at the beginning of the Ice Age (90 ka), the ice sheet
is prominent in the East but limited towards the West over Scandinavia.
During the Last Glacial Maximum, the situation is reversed. Note that
between each period represented here, there were periods when it was
relatively clear of ice and snow, with the disappearance of the ice sheet
located over the Sea of Barents and the separation into two sheets.
Adapted from Svendsen et al. (2004)
24 The Cryosphere and Sea Level
311