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| Titel |
Centennial-millennial scale variations in Western Antarctic Ice Sheet discharge and their relationship to climate and ocean changes during the late Holocene |
| VerfasserIn |
Frida Snilstveit Hoem, Ulysses S. Ninnemann, Helga (Kikki) F. Kleiven, Nil Irvali |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250150918
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| Publikation (Nr.) |
 EGU/EGU2017-15443.pdf |
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| Zusammenfassung |
| The Western Antarctic Ice Sheet (WAIS) may be highly sensitive to future warming and to
ocean driven changes in subsurface melting. Understanding this sensitivity is critical as WAIS
dynamics are a major source of uncertainty in sea level rise and regional climate
projections. Although there is increasing evidence that WAIS discharge has varied on
centennial to multi-millennial timescales since the last glacial period much less is
known about its most recent (late Holocene) behavior. This period is particularly
important as a baseline for delineating natural and anthropogenic influences and
understanding potential coupling between climate, ocean circulation, and WAIS
discharge.
Here we present high-resolution records of WAIS discharge together with co-registered
signals of surface and deep ocean physical property changes in a multicore taken from the
southern flank of the North Scotia Sea Ridge (53˚ 31.813 S; 44˚ 42.143 W at 2750m water
depth) spanning the past 4000 years. The site is situated just south/east of the polar front
beyond the reach of seasonal sea ice and its potentially confounding influence on the
ice-rafted debris (IRD) signal but still influenced by icebergs mostly originating from the
WAIS. Our record of IRD from core GS08-151-02MC provides a centennially resolved
record of iceberg supply from which we infer Antarctic ice-sheet dynamics and
variability, while we use the oxygen and carbon isotopic composition of benthic
(U. peregrina) and planktonic (N. pachyderma (s)) foraminifera to give (regional)
information on past polar deep water and surface water temperatures, circulation
and nutrients. Our results show higher amount of IRD between 4200-1800 cal yr
B.P. This is in agreement with paleoclimate records reconstructing the onset of the
neoglacial, sea ice expansion at about 5000 cal yr B.P. in the Atlantic sector of the
Southern Ocean, and glaciers advancing in South America. The strongest IRD peak of
the past millennium, which is otherwise a period of generally low IRD, coincides
with Little Ice Age at 600 cal yr B.P. The local surface water hydrography appears
relatively stable over the past 4000 years with the planktonic δ18O signal indicating
centennial-millennial scale changes of typically ≤1˚ C (Δ0.22) and notably smaller in
amplitude than the regional warming observed over the past century. The lack of
correlation between surface water physical properties and IRD in the downcore
records, suggests that IRD is not reflecting iceberg survival but rather changes in
the supply (WAIS dynamics) or routing. Consistent with this interpretation, IRD
covaries with climate on the Antarctic Peninsula (from JRI ice core) over the past 4
kyr with cooler conditions and lower amounts of IRD over much of the past two
millennia than occurred earlier in the neoglaciation. Both records indicate a recovery
with warming and increased IRD prior to industrialization. This relationship is
consistent with the hypothesis that climate and specifically ocean temperatures
were important for modulating WAIS discharge rates over the past few millennia. |
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