TY - ABST
T1 - Holocene glacial history of the west Greenland Ice Sheet inferred from cosmogenic exposure ages and threshold lakes
AU - Larsen, Nicolaj Krog
AU - Kjaer, K. H.
AU - Colding, Sune Oluf
AU - Funder, S.
AU - Kjeldsen, Kristian Kjellerup
AU - Odgaard, Bent Vad
AU - Olsen, J.
AU - Linge, H. C.
PY - 2011/12/1
Y1 - 2011/12/1
N2 - In this study, we use a combination of 10Be exposure ages and threshold
lakes to constrain the ice sheet history in Godthåbs- and
Buksefjorden, west Greenland (63-64°N) during the Holocene. The 10Be
cosmogenic exposure ages have been used to quantify both the ice retreat
and thinning of the west Greenland Ice Sheet in 3 transects from the
coast to the present ice margin. Preliminary results (n=47) indicate
initial deglaciation of coastal areas around 11 ka in concert with
existing radiocarbon chronology, followed by a rapid retreat from the
outer coast to the present ice margin around 10 ka. Boulder samples from
the highest peaks demonstrate that the ice was warm-based whereas
bedrock samples often contain an inherited signal. These results may
have implications for other studies in Greenland, which have inferred
thin LGM ice based on 10Be ages of bedrock samples. The threshold lakes
are used to record episodes when the ice sheet was close-to-the present
extent, represented by beds of clastic sediments whereas
gyttja-deposition reflects periods when the glacier was behind the
threshold, and no glacial meltwater input. Our results demonstrates that
following the initial deglaciation the ice margin remained close to the
present ice margin until around 7 cal. ka BP before it retreated behind
the present extent during the Holocene Thermal Maximum (HTM). Here it
remained until the Little Ice Age (LIA) where it readvanced to the
present position around 0.5 cal. ka BP. Our results correspond to other
recent findings from south and west Greenland that show that the ice
sheet first began to retreat behind the present ice margin around 7 cal.
ka BP. However, it differs from the other areas because the ice sheet
first reappears at the present ice position during the LIA (i.e. no
Neoglacial advance) and this suggest that the ice sheet in this area may
have been more retracted and probably more sensitive to climate change
than other areas in south and west Greenland.
AB - In this study, we use a combination of 10Be exposure ages and threshold
lakes to constrain the ice sheet history in Godthåbs- and
Buksefjorden, west Greenland (63-64°N) during the Holocene. The 10Be
cosmogenic exposure ages have been used to quantify both the ice retreat
and thinning of the west Greenland Ice Sheet in 3 transects from the
coast to the present ice margin. Preliminary results (n=47) indicate
initial deglaciation of coastal areas around 11 ka in concert with
existing radiocarbon chronology, followed by a rapid retreat from the
outer coast to the present ice margin around 10 ka. Boulder samples from
the highest peaks demonstrate that the ice was warm-based whereas
bedrock samples often contain an inherited signal. These results may
have implications for other studies in Greenland, which have inferred
thin LGM ice based on 10Be ages of bedrock samples. The threshold lakes
are used to record episodes when the ice sheet was close-to-the present
extent, represented by beds of clastic sediments whereas
gyttja-deposition reflects periods when the glacier was behind the
threshold, and no glacial meltwater input. Our results demonstrates that
following the initial deglaciation the ice margin remained close to the
present ice margin until around 7 cal. ka BP before it retreated behind
the present extent during the Holocene Thermal Maximum (HTM). Here it
remained until the Little Ice Age (LIA) where it readvanced to the
present position around 0.5 cal. ka BP. Our results correspond to other
recent findings from south and west Greenland that show that the ice
sheet first began to retreat behind the present ice margin around 7 cal.
ka BP. However, it differs from the other areas because the ice sheet
first reappears at the present ice position during the LIA (i.e. no
Neoglacial advance) and this suggest that the ice sheet in this area may
have been more retracted and probably more sensitive to climate change
than other areas in south and west Greenland.
KW - [0726] CRYOSPHERE / Ice sheets
KW - [1105] GEOCHRONOLOGY / Quaternary geochronology
KW - [1150] GEOCHRONOLOGY / Cosmogenic-nuclide exposure dating
KW - [1621] GLOBAL CHANGE / Cryospheric change
M3 - Conference abstract for conference
ER -
