On the Antarctic contribution to Holocene sea-level

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ON THE ANTARCTIC CONTRIBUTION TO
HOLOCENE SEA-LEVEL
BY
IAN DAVID GOODWIN
B. SURV., M. APP. SC. (U.N.S.W.)
Submitted in fulfilment of the requirements
for the degree of Doctor of Philosophy
in the Institute of Antarctic and Southern Ocean Studies (IASOS)
University of Tasmania
June, 1995
5v5- 500
STATEMENT
This thesis contains no material which has been accepted for the award of any other
degree, diploma or higher degree in any tertiary institution, except by way of
background information and duly acknowledged in the thesis, and to the best of my
knowledge and belief, this thesis contains no material previously published or written
by another person, except where due reference is made in the text of the thesis.
Ian David Goodwin
13 June, 1995
AUTHORITY OF ACCESS
This thesis may be made available for loan. Copying of any part of this thesis is
prohibited for six months from the date this statement was signed; after that time
limited copying is permitted in accordance with the Copyright Act 1968.
Ian David Goodwin
13 June, 1995
ACKNOWLEDGEMENTS
The research work which forms the core of this thesis was conducted whilst the author
was employed as a Glaciologist with the Glaciology Section, Australian Antarctic
Division from 1984 to 1990. Subsequently, the research work on the "Surface mass
balance variability in Kemp Land, East Antarctica" was conducted whilst the author
was employed as a Research Fellow in the School of Earth Sciences, University of
Melbourne, and funded by an Antarctic Scientific Advisory Committee (ASAC) Grant
to the author between 1991-1993. The later stages of thesis preparation were funded
by an Antarctic CRC Scholarship between August, 1994 to April, 1995.
The thesis was supervised by Dr Ian Allison, Principal Research Scientist, Glaciology
Program, Antarctic CRC and Australian Antarctic Division, and Professor Bill Budd,
Antarctic CRC, University of Tasmania. Over a number of years many of the author's
colleagues provided advice and actively participated in discussions and fieldwork
relevant to the thesis. The glaciological research was principally supervised by Mr
Neal Young, Dr Ian Allison and Mr Vin Morgan of the Glaciology Program. The
author is grateful for the friendship, discussion and co-operation of his colleagues in
the Glaciology Program over the last decade, especially Mr David Etheridge (CSIRO
DAR), Mr Egon Wehrle, Mr Martin Higham, Mr Russell Brand, Mr Damien Jones
and Mr Tim Medhurst. Mr Egon Wehrle developed specialised firn and ice coring
drills for the fieldwork. Mr Martin Higham and Mr Gerry Love conducted the drilling
program in Kemp Land in 1991/92 when the author was unable to participate.
Professor Pat Quilty provided direction, assistance and useful discussions on Antarctic
geoscience over the last decade, for which the author is grateful.
The extensive fieldwork which formed a major aspect of this research, involved
dozens of people. Firstly, I wish to acknowledge the assistance and friendship of my
fellow wintering ANARE expeditioners in 1985 at Casey Station, in particular, my
companions on the eastern Wilkes Land Traverses, with whom I worked and lived
continuously for fifteen months; Mr Ross Walsh, Mr Gerry Love, Mr Don Waugh,
Mr Wayne Eastley, Mr Graeme Lawrence, and Mr Andy Crook.
I also wish to acknowledge the assistance of many of the ANARE expeditioners at
Casey in 1985, 1986, 1987 and 1988 who accompanied the author on field trips along
the coast of Law Dome and on the Windmill Islands, and aided in the glacial
geological fieldwork, particularly Mr Ray Lindupp, Mr Russell Rachinger, Mr Blue
MacGibbon and Mr Simon Catley. I thank my ANARE colleagues at Mawson and at
the Dovers field base in the Northern Prince Charles Mountains in 1988/89,
particularly Dr Ian Allison, Mr Peter Mantell and Mr Rod Ledingham.
The author also thanks Dr Peter Barrett and Mr Alex Pyne, Antarctic Research Centre,
Victoria University of Wellington, New Zealand for the invitation and assistance to
participate in the 1989/90 NZARP summer program in glacial geological and
sedimentological fieldwork at Granite Harbour and Mackay Glacier environs,
McMurdo Sound, Victoria Land.
Many people assisted in the laboratory analysis of ice core samples and sediment
samples. These include: the late Mr Ted Wishart and Mr Colin Wookey at Glaciology
for some of the oxygen isotope analyses; Mr John Ivey and Ms. Diana Davies at
AGAL, Kingston for the solute analyses; Mr John Head at the Australian National
University Radiocarbon Laboratory for the 14C dating, and Mr John 01ley at CSIRO
Division of Water Resources for the deuterium isotope measurements.
The author also wishes to acknowledge the generous assistance of people in the
School of Earth Sciences, University of Melbourne, in particular Professor Ian
Simmonds and Dr Bob Baird, who provided an office and access to facilities whilst
this thesis was prepared.
Finally, I wish to thank my wife Deborah and children Angus and Erica for enduring
my absence both in Antarctica and for long bouts 'in the office', and my father Keith,
for encouragement. Last but not least, my thanks to Sir Edmund Hillary, who in 1968
inspired and encouraged me to seek adventure and science in the Antarctic.
ABSTRACT
Holocene glacial fluctuations of Antarctica are investigated using a combined glacial
geological and glaciological approach. An understanding of the timing, forcing and
sea-level contribution of these glacial fluctuations is crucial to the interpretation of
global eustatic sea-level changes during the Holocene and the present. As a baseline
for the Holocene studies, the recent surface mass balance rate distribution of Antarctica
and its controlling factors are determined with respect to case studies in the Wilkes
Land and the Lambert Glacier drainage basins. The variation in surface mass balance
rates and mean annual oxygen isotope values over the last 50 years are interpreted
from stratigraphic analyses of several shallow firn cores from these drainage basins.
The surface mass balance rate is calculated to vary with surface air temperature by
20%/°C in the ice sheet interior, and by 25%/°C in the coastal margins. This variation
is in response to changes in atmospheric circulation, surface air temperature and sea
ice extent.
The Holocene climate pattern is analysed with respect to the oxygen isotope records
from the deep ice cores and the oceanic sediment cores, and is defined into periods
where temperature has deviated up to 1-2°C from the long-term Holocene mean. The
corresponding terrestrial and marine glacial geological evidence for Holocene glacial
fluctuations in the south-western Pacific Ocean, the Indian Ocean, and the Ross Sea
sectors of East Antarctica is re-examined together with a case study of the Holocene
glacial history of the Windmill Islands and the Law Dome ice sheet, in East Antarctica.
An interpretation of the ice expansion during the Last Glacial Maximum and the
subsequent melting history of the Law Dome ice sheet during the Early-Mid Holocene,
is made from field observations of raised shorelines and the chronostratigraphy of lake
sediments and abandoned Adelie penguin rookeries on the Windmill Islands. The
Mid-Late Holocene evolution of the Law Dome ice sheet margin is determined from
the stratigraphy, structure, morphology, isotopic, solute and sediment composition of
basal ice exposures and the Loken Moraines. The results from the Law Dome case
study support the view that contraction of the outlet glaciers was established before
8,000 years B.P. with the outer Windmill Islands, adjacent to the Vanderford Glacier,
ice free at this time. Contraction of the grounded ice margins lagged the outlet glaciers
with the inner Windmill Islands deglaciated by 5,500 years B.P.. Subsequently, the
ice margin continued to retreat to a position further inland than the present until 4,500
years B.P.. During this period the East Antarctic outlet glaciers were at their
maximum Holocene expansion. Between 4,000 to 1,000 years B.P. it is concluded
that the Law Dome and the East Antarctic grounded ice margins expanded with a
partial contraction between 500 years B.P. to the present.
111
Relative sea-level changes and variation in surface mass balance rates throughout the
Holocene are tested by a sensitivity analysis of the Lambert Glacier/Amery Ice Shelf
system, the Law Dome and Wilkes Land to determine the forcing mechanisms for the
glacial fluctuations. The palaeo-surface mass balance rates are calculated for the Early
Holocene Climatic Optimum, the Mid Holocene cool period, and the Late Holocene
warm and cool phases, using the interpreted 20-25%/°C variation in surface mass
balance with air temperature. The sensitivity analyses confirm that the size of
Antarctica is controlled by its dual response to sea-level and climate changes, with
expansion initiated by relative sea-level lowering and nourished by a positive surface
mass balance. The relative sensitivities are characterised by the outlet glaciers leading
the grounded ice sheet margins and the alpine glaciers, both in the Early Holocene
contraction and in the Mid-Late Holocene expansion. It is hypothesised that variation
in palaeo-surface mass balance rates during the Holocene has partially offset the sea-
level rise contribution of the post-glacial contraction of Antarctica. An equivalent sea-
level curve for Antarctica is constructed from the differential surface mass balance
contributions and from the post-glacial melting history. The validity of the hypothesis
is tested by comparing the derived sea-level curve to the relative sea-level records on
mid-oceanic islands. The maximum contribution from Antarctica to post-glacial sea-
levels occurred at 4,000 years B.P. when there was widespread retreat of the East
Antarctic outlet glaciers, and the grounded ice sheet margins. This is synchronous
with the geomorphological evidence for high sea-level stands on the mid-oceanic
islands. Antarctica contributed a slight lowering to sea-level between 4,000 to 1,000
years B.P.. During this century the probable Antarctic sea-level contribution was
calculated to have varied from a sea-level contribution of +0.25 mm a -1 prior to 1970
followed by a contribution of -0.15 mm a-1 since 1970. It is suggested that these
contributions to Holocene sea-levels provide a better fit to the oceanic sea-level records
than those produced by models based on the continuing exponential melting and retreat
of the Antarctic Ice Sheet throughout the Holocene.
iv
TABLE OF CONTENTS
Acknowledgements
Abstract
iii
List of Figures xi
List of Tables xv
1 INTRODUCTION 1
1.1 Overview 1
1.2 Characteristics Of Holocene Climate In Antarctica 5
1.3 Review Of Factors Determining Sea Level 21
1.4 Review Of The Present Sea-Level Contribution Of Antarctica 24
2 SPATIAL VARIATION OF SURFACE MASS BALANCE
IN EAST ANTARCTICA 26
2.1 Introduction 26
2.2 Regional Setting Of The East Antarctic Katabatic Zone 28
2.3 Snow Accumulation And Surface Topography In Wilkes Land 31
2.3.1 Regional Surface Topography 31
2.3.2 Snow Accumulation Rates 31
2.3.2.1 Eastern and Western Wilkes Land 31
2.3.2.2 Southern Wilkes Land 35
2.3.3 Accumulation-Elevation Relationships 35
2.3.4 Wilkes Land Drainage Basin Accumulation Distribution 36
2.4 Snow Accumulation And Surface Topography In The Lambert
Glacier Basin 38
2.4.1 Regional Surface Topography 38
2.4.2 Snow Accumulation Rates 38
2.4.3 Lambert Glacier Basin Accumulation Distribution 41
2.5 Snow Redistribution Processes: A Case Study of Surface Microrelief
In Eastern Wilkes Land 43
2.6 Katabatic Surface Wind Pattern and Snow Redistribution 48
2.7 Overview Of The Regional Surface Mass Balance Pattern 52
3 TEMPORAL VARIATION OF SURFACE MASS BALANCE
AND OXYGEN ISOTOPES IN EAST ANTARCTICA 55
3.1 Introduction 55
3.2 Background On The Oxygen Isotope Composition Of Antarctic Snow
And Firn . 56
3.3 Development Of A Firn Stratigraphic Model And Stratigraphic
Methods For The Katabatic Zone 58
3.3.1 Seasonal Development Of The Surface Snow Layer 58
3.3.2 Firn Stratigraphic Methods 59
3.4 Wilkes Land And Queen Mary Land Temporal Accumulation Patterns 62
3.4.1 Oxygen Isotope Stratigraphy And Accumulation Rates
In Wilkes Land, Law Dome And Queen Mary Land 62
3.4.1.1 GDO3 Core 62
3.4.1.2 GDO6 Core 63
3.4.1.3 GD15 Core 63
3.4.1.4 GF12 Core 64
3.4.2 Temporal Variation Of Accumulation Rate And Oxygen
Isotope In Wilkes Land, Law Dome And Queen Mary
Land 64
3.5 Lambert Glacier Basin, Mac.Robertson Land And Eastern Kemp
Land Temporal Accumulation Patterns 74
3.5.1 Oxygen Isotope Stratigraphy And Accumulation Rates
At LGBOO, MGA And E065 74
3.5.2 Temporal Variation Of Accumulation Rate And
Oxygen Isotope In Eastern Kemp Land 76
3.6 Amery Ice Shelf Temporal Accumulation Rate Patterns 80
3.7 On The Relationship Between Accumulation Rate, Oxygen
Isotope Composition And Climate Parameters 83
3.7.1 Air Temperature 83
3.7.2 Sea Ice Extent, Concentration And Atmospheric
Circulation 84
3.8 Regional Analysis Of Accumulation Rate And Oxygen Isotope
With Air Temperature And Sea Ice Extent Variations 85
3.8.1 Wilkes and Law Dome 86
3.8.2 Queen Mary Land 92
3.8.3 Mac.Robertson and Kemp Lands 95
3.9 Discussion On The East Antarctic Temporal Accumulation Pattern 99
3.10 Accumulation-Temperature And Accumulation-Sea Ice Extent
Relationships 102
vi
4 LATE PLEISTOCENE-MID HOLOCENE GLACIAL
HISTORY, COASTAL EVOLUTION AND SEA LEVEL
CHANGES AT THE EAST ANTARCTIC ICE MARGIN:
A CASE STUDY OF LAW DOME 107
4.1 Introduction 107
4.2 Evidence of Late Pleistocene Glaciation 110
4.3 Surficial Sediment Cover 111
4.4 Raised Marine Shorelines 112
4.5 Radiocarbon Age Determination And Reservoir Effects 116
4.6 Lake and Pond Sediments 117
4.6.1 Ho11 Lake, central Ho!! Island 119
4.6.2 Ho11 Pond A, northern Ho11 Island 119
4.6.3 Bailey Pond, northwestern Bailey Peninsula 122
4.6.4 Mitchell Pond B, western Mitchell Peninsula 123
4.6.5 Shirley Pond, Shirley Island 123
4.7 Abandoned Adelie Penguin Rookeries 123
4.8 14C Chronology Of Deglaciation And Glacio-Isostatic Uplift 126
4.9 Comparison Of Glacio-Isostatic Uplift At The Windmill Islands
With That Determined From East Antarctic Raised Beaches 131
4.10 On The Contribution Of East Antarctica To Eustatic Sea-Level
Lowering At LGM 135
5 THE MID-LATE HOLOCENE GLACIAL HISTORY OF
THE LAW DOME ICE MARGIN 139
5.1 Introduction 139
5.2 Morphology of the Ice Ramp 139
5.3 Morphology of the LOken Moraines 141
5.4 A Study On the Evolution of the Basal Ice Zone 149
5.4.1 Geographic Setting 149
5.4.2 Ice Cliff Sampling 151
5.4.3 Basal Ice Types and Stratigraphy 151
5.4.3.1 Debris-Free Ice Types 153
5.4.3.2 Debris Bearing Ice Types 156
5.4.4 Co-Isotopic Composition Of Basal Ice 157
5.4.5 Marine Ice Characteristics and Accretion 159
5.4.6 Modes Of Subglacial Debris Entrainment And Ice
Accretion 162
5.4.7 Sediment Characteristics Of The Type 5 Debris Band Ice 166
5.4.7.1 Proglacial Sediments 168
VII