Skip to main content
Article thumbnail
Location of Repository

Deglacial history of the West Antarctic Ice Sheet in the western Amundsen Sea Embayment

By James A. Smith, Claus-Dieter Hillenbrand, Gerhard Kuhn, Robert D. Larter, Alastair G.C. Graham, Werner Ehrmann, Steven G. Moreton and Matthias Forwick

Abstract

The Amundsen Sea Embayment (ASE) drains approximately 35% of the West Antarctic Ice Sheet (WAIS) and is one of the most rapidly changing parts of the cryosphere. In order to predict future ice sheet behaviour, modellers require long-term records of ice-sheet melting to constrain and build confidence in their simulations. Here, we present detailed marine geological and radiocarbon data along three palaeo-ice stream tributary troughs in the western ASE to establish vital information on the timing of deglaciation of the WAIS since the Last Glacial Maximum (LGM). We have undertaken multi-proxy analyses of the cores (core description, shear strength, x-radiographs, magnetic susceptibility, wet bulk density, total organic carbon/nitrogen, carbonate content and clay mineral analyses) in order to: (1) characterise the sedimentological facies and depositional environments; and (2) identify the horizon(s) in each core that would yield the most reliable age for deglaciation. In accordance with previous studies we identify three key facies, which offer the most reliable stratigraphies for dating deglaciation by recording the transition from a grounded ice sheet to open marine environments. These facies are: i) subglacial, ii) proximal grounding line, and iii) seasonal open marine. In addition, we incorporate ages from other facies (e.g., glaciomarine diamictons deposited at some distance from the grounding line, such as glaciogenic debris flows and iceberg-rafted diamictons and turbates) into our deglacial model. In total, we have dated 78 samples (mainly the acid insoluble organic (AIO) fraction, but also calcareous foraminifers), which include 63 downcore and 15 surface samples. Through careful sample selection prior to dating, we have established a robust deglacial chronology for this sector of the WAIS. Our data show that deglaciation of the western ASE was probably underway as early as 22,351 calibrated years before present (cal yr BP), reaching the mid-shelf by 13,837 cal yr BP and the inner shelf to within c.10-12 km of the present ice shelf front between 12,618 and 10,072 cal yr BR The deglacial steps in the western ASE broadly coincide with the rapid rises in sea-level associated with global meltwater pulses 1 a and 1b, although given the potential dating uncertainty, additional, more precise ages are required before these findings can be fully substantiated. Finally, we show that the rate of ice-sheet retreat increased across the deep (up to 1600 m) basins of the inner shelf, highlighting the importance of reverse slope and pinning points in accelerated phases of deglaciation

Topics: Glaciology
Publisher: Elsevier
Year: 2011
DOI identifier: 10.1016/j.quascirev.2010.11.020
OAI identifier: oai:nora.nerc.ac.uk:14112

Suggested articles

Citations

  1. (c) Getz B (b) Getz A (a) Dotson
  2. (2000). (k m ) (d) mid-inner shelf deglaciation envelope 0
  3. (kPa) Grain size (%) Corg% Smectite/Chlorite yr BP Supplementary Figure 1e-g. * D ep th (c m
  4. (2000). 14C dataWater content (%) MS x 10-5 (SI Units) Clay mineral data 14C dataWater content (%) MS x 10-5 (SI Unit) Clay mineral data D ep th (c m )
  5. (1989). 21 Algal age (Bockheim
  6. (1963). 5 - 1200 m/yr (Pine Island Glacier,
  7. ages plot above any apparent 14C dog-leg in the age-depth plots (Fig.
  8. (2010). An improved Antarctic dataset for high 1121 resolution numerical ice sheet models (ALBMAP
  9. (1219). Antarctic sediment chronology by programmed-temperature pyrolysis: 1220 methodology and data treatment. Geochemistry, Geophysics, Geosystems 9, Q04005. 1221 doi:10.1029/2007GC001816. 1222 1223 Schoof, C.,
  10. (1999). argued that retreat of the grounding line from the outer Drygalski Trough to Ross 732 Island is likely to have contributed to mwp-1b (Fig. 6), whilst a Ross Sea contribution 733 to mwp-1a has been ruled out by Domack
  11. (2004). Continental slope morphology 1002 and sedimentary processes at the mouth of an Antarctic palaeo-ice stream. Marine 1003 Geology 204, 203– 214.
  12. (2006). Expansion and rapid retreat of the West 1169 Antarctic Ice Sheet in Eastern Ross Sea: possible consequence of over extended ice 1170 streams?
  13. F po in t se n so r S h e a r stre n g t h W a t e r co n t e n t G ra in -size T C C org N t o t Cla y m in e ra l
  14. (2002). Heroy
  15. (2005). Ice-sheet extent of the Antarctic Peninsula region 1049 during the Last Glacial Maximum (LGM) – Insights from glacial geomorphology. 1050 doi
  16. (2006). If correct, the deglacial ages from the 708 western ASE/Bellingshausen Sea sector of the WAIS indicate deglaciation was 709 underway earlier than previously thought (cf. Anderson et al.,
  17. (2005). implications for a Last Glacial Maximum grounding line.
  18. (2010). in the southern Bellingshausen Sea reveals drainage changes of the West Antarctic Ice 1073 Sheet during the Late Quaternary. Marine Geology 265, doi
  19. (2006). Island/Thwaites palaeo ice stream trough Figure 1 D ep th (c m
  20. (2005). Marine Radiocarbon Calibration Curve 1027 Spanning 0 to 50,000 Years B.P. doi
  21. (2007). Modelling Antarctic 929 sea-level data to explore the possibility of a dominant Antarctic contribution to 930 Meltwater Pulse IA. doi
  22. (1999). O’Brien and an anonymous reviewer are greatly appreciated and have helped 905 improve the clarity of our paper. 906 907 10. References 908 909
  23. (1999). Past 978 and future grounding-line retreat of the West Antarctic Ice Sheet. Science 286, 280–979 283. 980 981 doi
  24. (2004). Recent 1194 dramatic thinning of largest West Antarctic ice stream triggered by oceans. 1195 Geophysical Research Letters 31, L23401,
  25. (2005). Relative 1270 sea-level history from the Lambert glacier region, East Antarctica, and its relation to 1271 deglaciation and Holocene glacier readvance.
  26. Reserv oir C o r r e c t e d 1 4 C C a l i b r a t e d Age ±1s Code Lat. Long. (cmbsf ) D a t e d Age (yrs BP) correction
  27. (1999). Retreat trajectory for the deglaciation of the WAIS in the western 1365 Amundsen Sea. Calculated average retreat rates are shown together with the trajectory 1366 of modern and palaeo retreat rates (numbered lines, bottom left panel) for Ice Stream 1367 B
  28. (1098). S.G., in press. Ice stream retreat and ice shelf history in Marguerite Trough, Antarctic 1099 Peninsula: sedimentological and foraminiferal signatures. Geological Society of 1100 America Bulletin, in press.
  29. Shear strength (kPa) Grain size (%)
  30. Supplementary Figure 1k-n. D ep th (c m ) D ep th (c m
  31. (2009). The 1243 sediment infill of subglacial meltwater channels on the West Antarctic continental 1244 shelf.
  32. (1995). the maximum duration of GZW formation, which is consistent with the time span 607 estimated for the deposition of a GZW on the western Antarctic Peninsula shelf 608 (Larter and Vanneste,
  33. (1998). was probably deposited in a glaciomarine environment proximal to 381 the grounding line of the ice stream, subsequent to its retreat from the core site (e.g., 382 Domack et al.,

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.