ICE SHEES AND LATE QUATERNARY ENVIRONMENTAL CHANGE
Martin J. Siegert
Bristol Glaciology Centre, School of Geographical Sciences,
University of Bristol, Bristol BS8 1SSAugust 2000
CONTENTS
CHAPTER 1. CAUSES OF ICE AGES
Introduction
Growth and decay of terrestrial glaciers
Milankovitch Theory
i. Orbital eccentricity.
ii. Changes in axis inclination (obliquity).
iii. Precession of the equinoxes.
Amplifying factors and feedback mechanisms
Sea level.
Surface Albedo.
Carbon Dioxide.
Ice-sheet elevation.
Ocean circulation.
Concluding remarks on feedback and ice-age forcing.
Recent theories for 100,000 year glacial cycles
Inclination of Earth Orbital plane
Potential cyclicity within the thermohaline ocean conveyor
Recent evidence from the last interglacial
CHAPTER 2. INDICATORS OF ICE VOLUME AND CLIMATE CHANGE
A. RECORDS OF GLOBAL CLIMATE CHANGE
Introduction
Ocean floor sediments at abyssal depths
Deep ice cores
Oxygen isotope records
Isotopic concentrations and ice cores.
Isotopic concentrations and sea floor sediments.
Deep-sea Oxygen isotope data and MILANKOVITCH forcing.
Mg/Ca palaeothermometry from sea-floor sediments
Further information from ice cores
Snow fall analysis from ice core studies
Carbon Dioxide analysis from ice core studies
Chemical signatures in ice cores
Dust in ice cores
Ash and volcanic activity recorded in ice cores
Cosmogenic radionuclides in ice cores
Carbonate recordsB. RECORDS OF GLOBALSEA-LEVEL CHANGE
Introduction
Global sea-level curve
Sea-level variation within the glaciated regions.
Relative sea-level and glacial isostasy.C. CONCLUDING REMARKS
CHAPTER 3. THE FLOW OF ICE AND ICE-SHEET MODELLING
The flow of glaciers and ice sheets
Internal Deformation of Ice:
Basal Sliding:
Basal Sediment Deformation:
Non-Steady and Fast Glacier Motion:
Glacial Isostasy
Asthenospheric diffusion.
Lithospheric displacement.
Ice sheet models
Feedback within ice-sheet models
CHAPTER 4. LATE QUATERNARY GEOLOGY I.
Terrestrial: glacial morphology and sedimentologyA. GLACIAL EROSION FEATURES
Introduction
Glacial (ice) erosion processes
Abrasion
Plucking
Regelation
Glaci-erosional landforms:
Rock Crushing
Erosion of ice combined with frost action
Pressure release and dilationB. SUBGLACIAL WATER ACTIVITY
C. GLACIAL SEDIMENTATION AND DEPOSITION
Landforms formed subglacially, parallel to ice flow
Drumlins.
Drumlinoid ridges, or drumlinised ground moraine:
Flutes and fluted moraines;
Landforms formed subglacially, transverse to ice flow
Ribbed moraines (or rogen moraines).D. TERRESTRIAL GLACIAL GEOOGY AND ICE SHEET RECONSTRUCTIONS
CHAPTER 5. LATE QUATERNARY GEOLOGY II.
Raised shorelines & Continental shelfRaised shorelines and isostatic uplift
Glaci-marine sedimentation
Lakes (glaci-lacustrine sedimentation)
The physical character of glacially-fed or ice-dammed lakes.
Glaci-lacustrine sedimentary processes.
Landforms from glaci-lacustrine deposition.
Other information from lacustrine environments.
Continental Shelf (shallow marine sedimentation)
Introduction.
Transport of sediment out of the ice-sheet system.
Icebergs from grounded margins of ice sheets.
Ice shelves and icebergs.
Sedimentation rates.
Glacial erosion and deposition over the marine-based continental shelf.
CHAPTER 6. LATE QUATERNARY GEOLOGY III.
Continental shelf-break sediments & Deep Sea environments and iceberg debris.Trough-fan complexes
Rates of sedimentation over glaci-genic fans
Marine geological data: Fan distribution and structure
A Qualitative Model for Sedimentation on Glacier-Influenced Margins.
Deep sea environments
Spatial distribution of IRD
Heinrich layers
Local variations in the palaeo-environmental signals
CHAPTER 7. LATE QUATERNARY PALAEOCLIMATE
Introduction
Geological information on palaeoclimate
Examples of ice-core-geological data inter-comparison.
Modern climate controls (polar atmospheric circulation)
Climate models of the last glacial maximum within the Northern Hemisphere
a. CLIMAP
b. GCM modelling
Eemian Interglacial.
Last glacial.
The Laurentide ice sheet.
Effect of sea-surface temperatures on the Eurasian ice sheet.
LGM global climate transect
CHAPTER 8. LGM PALAEOCEANOGRAPHY
Introduction
Ocean influence on climate: present day
1. Surface currents.
2. Oceanic conveyor belt.
Ocean influence on climate during the last glaciation
Surface ocean currents under a CLIMAP-type glacial scenario.
Surface currents under a non-CLIMAP-type scenario.
Ocean conveyor circulation: A glacial cycle situation (Imbrie et al 1992).
Interglacial state.
Preglacial state.
Glacial state.
Deglacial state.
Short-term changes in ocean conditions and climate
CHAPTER 9. ICE SHEET RECONSTRUCTIONS I
The Antarctic Ice SheetA very brief introduction to the Antarctic Ice Sheet
A. GEOLOGICAL INFORMATION
Pre Quaternary ice-sheet history
Basic LGM issues
Geological information for Late Quaternary Antarctic ice-sheet change
Last interglacial:
Last glacial:
CLIMAP reconstruction for the LGM:
Drewry hypothesis:
Post CLIMAP scenarios
Ross Sea glaciation.
Prydz Bay and the Lambert Amery system.
Antarctic Peninsula.
Further support for CLIMAP ice extent:
Evidence for Heinrich-style IRD events from the Antarctic Ice Sheet
Holocene retreat of iceB. NUMERICAL MODELLING INFORMATION
Glaciological ice-sheet modelling
Ice Sheet sensitivity
Antarctic ice sheet reconstruction through the last glacial cycle.
Modelling of the ice sheet in Dronning Maud LandResults from isostatic modelling of post-glacial uplift and the contribution to global sea-level
C. SUMMARY OF THE GLACIAL HISTORY AND THE CONTRIBUTION TO LGM GLOBAL SEA-LEVEL FALL.
CHAPTER 10. ICE SHEET RECONSTRUCTIONS II
The Greenland Ice SheetA very brief introduction to the Greenland Ice Sheet
A. GEOLOGICAL INFORMATION
Introduction
The last glacial maximum
West Greenland.
North Greenland.
East Greenland.
South Greenland.
Evidence from ice cores.
Summary of Deglaciation.
Ice core evidence for rapid climate changes over Greenland.
Uplift historyB. NUMERICAL MODELLING INFORMATION
Glaciological ice sheet modelling
Introduction
Glacial-interglacial results
Ice-sheet sensitivity experiments
Future workIsostatic modelling
C. SUMMARY OF THE GLACIAL HISTORY AND THE CONTRIBUTION TO LGM GLOBAL SEA-LEVEL FALL.
CHAPTER 11. ICE SHEET RECONSTRUCTIONS III.
3. Eurasian High Arctic ice sheets (Barents Ice Sheet), 4. Scandinavian Ice Sheet, 5. British Isles Ice SheetIntroduction
Modern and ancient climate controls for the European Arctic
Modern climate
Ancient climate (geological and oceanographic information)British Isles Ice Sheet.
Scandinavian Ice Sheet
Geological records
LGM.
Deglaciation.
Numerical modelling studies
European ice sheet and Heinrich layers?Eurasian High Arctic Ice Sheet
Weichselian glaciations
High productivity zones: conditions for ice sheet growth.
Ice rafted debris (IRD) and (18O records.
Geological evidence for ice-sheet extent.
Previous Late Weichselian ice sheet reconstructions.
Proponents of the ëMaximumí ice mass idea:
Opponents of the Maximum ice mass:A. GEOLOGICAL INFORMATION FOR THE ONSET OF LATE WEICHSELIAN GLACIATION AND THE LGM
Onset of glacial activity.
Onset within the western Barents Sea.
Surrounding ocean conditions.
LGM Ice sheet limits
Sedimentary fan systems across the Eurasian continental margin.
Eastern margin - Severnaya Zemlya.
Southern margin of the ice sheet.
Mechanisms for the glacierisation of the Eurasian Arctic seas.B. NUMERICAL ICE SHEET MODELS
Weichselian glaciations
Late Weichselian ice sheet
Maximum sized ice sheet
Minimum ice sheet
Palaeoclimate reconstruction for Late Weichselian
Isostatic modelling:
Geological data - Deglaciation
Ice sheet modelling - deglaciation
Isostatic modelling of ice-sheet decayC. SUMMARY OF THE LATE QUATERNARY GLACIATION OF THE EURASIAN ARCTIC
Chapter 12. ICE SHEET RECONSTRUCTIONS IV.
North America. 6. Laurentide Ice Sheet, 7. Cordilleran Ice Sheet. 8. Innuitian Ice SheetA. GEOLOGICAL EVIDENCE
Introduction
Present day ice masses in North America
Onset of ice growth (Late Wisconsin)
Maximum extent of ice sheets
Cordilleran Ice Sheet and the northwest of North America.
Laurentide Ice Sheet.
Extent of ice during ice sheet decay
Ice sheet decay and the formation of lobes.
Ice-sheet decay and the formation of proglacial lakes.
The chronology of proglacial Lakes Agassiz, Algonquin and Ojibway.
The effect of proglacial lakes on climate and ice-sheet dynamics.
Brief summary of proglacial lake chronology.
Raised beaches and post glacial isostatic uplift.
Production of icebergs from the Laurentide ice sheet.
Climatology of the Pleistocene-Holocene Transition
Deglaciation of the Cordilleran Ice Sheet.
Possibility of subglacial lake outbursts during deglaciation
Further inspection of the Laurentide ice sheet glacial geology and unstable flow of ice
B. NUMERICAL MODELS OF THE WISCONSIN NORTH AMERICAN ICE SHEETS
LGM Ice sheet configuration.
Time-dependent growth of ice.
Geological and topographic control on ice-sheet dynamics.
Unstable ice flow and ice stream thermo-mechanics.
Time-dependent numerical studies of deglaciation.
Ice-Ocean interactions: Heinrich events
Implications for Oceanic circulation
The Late Wisconsinan Innuitian Ice SheetC. GLACIATION OF OTHER PARTS OF NORTH AMERICA
Alaska and the Brooks Range.
Aleutian Islands.
Rocky Mountain National Parks.
Sierra Nevada.
Glacial History of Mexico and central AmericaD. SUMMARY OF THE GLACIATION OF NORTH AMERICA
Chapter 13. ICE SHEET RECONSTRUCTIONS V.
Remaining LGM ice cover. 9. Iceland, 10. South America: Patagonia and the Andes, 11. South Island (New Zealand), and Tasmania, 12. Glaciation of mainland Europe, 13. Tibet.Introduction
Iceland
South America
Patagonian ice cap
Equatorial Andes
New Zealand and Australia
South Island
Tasmania
Glaciation on Mauna Kea, Hawaii
Europe
The glaciation of Tibet
Calculations of Global Sea-level at the LGM
ICE SHEETS AND LATE QUATERNARY ENVIRONMENTAL CHANGEMartin J. Siegert
Preface
In 1981 Denton and Hughes published 'The last great ice sheets'; a seminal work detailing the configuration of Late Quaternary ice sheets based mainly on interpretation of geological evidence. Since then, there have been a number of advances in subjects involved in the reconstruction of former ice sheets. A first is an abundance of recent geological evidence (from land, sea and ocean) that supplements and adds to that available in 1981. A second is the wide use of numerical ice-sheet modelling as a tool for quantifying the growth, decay and flow of former ice-sheets. A third is an appreciation for how ice-sheets, climate and oceans interact. Because of these developments (and probably some others), several of the ice-sheet reconstructions detailed in ëThe last great ice sheetsí have been revised. Despite this, however, many scientists today refer to Denton and Hughesí reconstructions because, I believe, the most recent ideas on late Quaternary ice sheets have not, until now, been collated.
This book has three main aims. First to detail how Late Quaternary ice sheets can be reconstructed. Second to present the dimensions and dynamics of these former ice sheets and show how these changed over the last ice age. Third, to indicate how Late Quaternary ice sheets were an interactive element of the global environment. Although the book is intended as an undergraduate text I hope the work presented in it will also benefit researchers requiring information about recent advances in our comprehension of Late Quaternary ice sheets.
We currently know enough about Late Quaternary ice sheets to realise that our knowledge is incomplete. So, although few things are certain in science, one thing I can predict with confidence is that the information in this book will require revision as new evidence presents itself. Until then, I hope that this book will provide a useful guide to the ice sheets of the Late Quaternary.
Martin J. Siegert
Bristol Glaciology Centre, August 2000
Reference
Denton, G.H., and Hughes, T.J. 1981. The last great ice sheets. John Wiley and Sons, New York. 484 pp.