Synchronous terminus change of East Antarctic outlet glaciers linked to climatic forcing Bertie Miles

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Durham E-Theses
Synchronous terminus change of East Antarctic outlet
glaciers linked to climatic forcing
MILES, BERTIE
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2
Bertie Miles
Synchronous terminus change of East Antarctic outlet
glaciers linked to climatic forcing
In recent years there has been a growing trend of acceleration, thinning and
retreat of ocean-terminating outlet glaciers in both the Greenland and West
Antarctic Ice Sheets, resulting in an increasing contribution to sea level rise.
Similar changes in glacier elevation have been observed in major marine basins of
the much larger East Antarctic Ice Sheet, but there are few measurements of
glacier terminus positions. In this study, the frontal position of 175 marine
terminating glaciers along a 5,400 km stretch of the East Antarctic coastline is
analysed. Overall, between 1974 and 2010 there was little change in glacier frontal
position (median: 0.7 m a-1). However, strong decadal trends have been observed,
from 1974 to 1990, the majority of glaciers retreated (63%), whereas between
1990 and 2000, most glaciers advanced (72%), a pattern which dropped to fewer
glaciers advancing (58%) in the most recent decade (2000 to 2010). The patterns
in glacier frontal position change are consistent with a rapid and coherent
response to atmospheric and oceanic/sea-ice forcing, which are ultimately driven
by the dominant mode of atmospheric variability in the Southern hemisphere, the
Southern Annular Mode. This indicates that the East Antarctic Ice Sheet may be
more vulnerable to climate change than previously recognised. However, unlike in
Greenland, there appears to be no clear link between recent changes in glacier
elevation and frontal position, possibly due to the unconstrained (~90%) nature of
the majority of glaciers in the study area.

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Synchronous terminus change of East
Antarctic outlet glaciers linked to climatic
forcing

Bertie Miles

Thesis submitted for the degree of Master of Science

Department of Geography
Durham University

November, 2012

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TABLE OF CONTENTS

Title Page i
Contents iii
List of Tables v
List of Figures vi
Statement of Copyright vii
Acknowledgements viii
1. INTRODUCTION 1-4
1.1 Significance of Ice Sheets 1
1.2 Remote Sensing of Ice Sheets 1-2
1.3 East Antarctica 2
1.4 Thesis aims and objectives 3-4
1.5 Study area 4
2. A REVIEW INTO RECENT ICE SHEET AND OUTLET GLACIER
TRENDS 5-14
2.1 Introduction 5
2.2.1 Wider importance and drivers of outlet glacier evolution 5-6
2.2.2 Conditions at the calving terminus and glacier de-buttressing 6
2.2.3 Calving 6-7
2.3 Recent changes in Ice Sheets 8-14
2.3.1 Greenland 8-9
2.3.2 Antarctica 9-14
2.3.2.1 West Antarctica 10-12
2.3.2.2 East Antarctica 12-13
3. METHODS 14-28
3.1 Introduction 14
3.2 Overview of data sources 14-17
3.2.1 Landsat imagery 16
3.2.2 AGRON imagery 16-17
3.3 Co-registration 17-18
3.3.1 Landsat co-registration 17-18
3.3.2 ARGON co-registration 18
3.4 Data acquisition 28-25
3.4.1 Mapping 18-19
3.4.2 Glacier Identification 20
3.4.3 Calculating glacier change 20-21
3.4.4 Grounding lines, ice velocity and elevation change 22-25
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3.5 Error analysis 25-28
3.6 Climate data 28
4. RESULTS 29-50
4.1 Summary of glacier change measurements 29-31
4.2 Glacier frontal change 31-37
4.2.1 An overview of glacier change between 1974 (1963)
and 2010 31-32
4.2.2 Decadal fluctuations 32-37
4.3 Glacier frontal position change in relation to width and velocity 38-43
4.3.1 Case studies 41-43
4.4 Glacier change and elevation 44
4.5 Glacier change and climate 44-46
4.6 Statistical analysis 47-50
4.7 Summary 50-51
5. EAST ANTARCTIC CLIMATE AND GLACIER CHANGE 52-62
5.1 Relationship between glacier frontal change and climate 52-62
5.1.1 Air temperature 52-53
5.1.2 Sea Ice 53-57
5.1.3 Ocean forcing 57-59
5.1.4 Southern Annular Mode 59-62
5.2 Relationship to glacier frontal change 62-66
5.3 Glacier elevation change 66-68
5. DISSCUSSION 52-62
6.1 Relationship to glacier frontal change 63-67
6.2 Glacier elevation change 67-69
6. CONCLUSIONS 70-73
7. REFERENCES 74-90

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List of Tables

3.1 Image resolution and scene size for each time step 15
3.2 The amount of data lost at each time step 19
3.3 Terminus digitization error 26
3.4 Estimated co-registration error for each mosaic and at each time step 27
3.5 Estimated total error for each mosaic at each time step 28
3.6 Spatial information for the research stations used in this study 28
4.1 Number of glaciers successfully mapped 29
4.2 Drainage basin characteristics 31
4.3 Long term glacier terminus change 32
4.4 Decadal changes in glacier frontal position 33
4.5 Glacier frontal position change in 2000-2006 and 2006-2010 37
4.6 Mean summer temperature during the time periods of glacier change 45
4.7 Mean annual temperatures 46
4.8 t-test for significant difference between glacier frontal position change between
1974-1990 and 1990-2000 48
4.9 t-test for significant difference between glacier frontal position change between
the 20 most northerly and 20 most southerly glaciers in DB15 49
4.10 t-test for significant difference between glacier frontal position change
between 1990-2000 and 2000-2010 49-50
4.11 t-test for significant differences in mean austral summer temperature between
1974-1990 and 1990-2000, and 2000-2010 50

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List of Figures

1.1 Number of published studies related to Greenland, West Antarctica and
East Antarctica 3
1.2 Map of the study area 4
2.1 Glacier elevation change in Greenland and Antarctica
(Pritchard et al., 2009) 9
2.2 Mass change in Antarctica (King et al., 2012) 10
2.3 Bed topography of East Antarctica showing the Aurora subglacial basin
(Young et al., 2011) 13
3.1 Overlay of available images at each time period 15
3.2 Contrast between Landsat SLC-on and SLC-off 16
3.3 Overlay of the mosaics created 18
3.4 Example of the box method used to map glacier change 21
3.5 Extraction of glacier velocity data 23
3.6 Satellite crossover paths associated with glacier elevation change 24
3.7 Spatial location of the elevation data extracted 25
3.8 Example of a calved glacier front 26
4.1 Spatial location of the 175 glaciers mapped 30
4.2 Histograms showing glacier frontal position change at each near decadal time
step 34
4.3 Spatial and temporal variations in glacier frontal position change 35
4.4 Trends in glacier frontal position change by drainage basins 37
4.5 Trends between glacier range, width and velocity 38
4.6 Glacier frontal position change in relation to glacier width classes 39
4.7 Glacier width in each drainage basin 40
4.8 Fluctuations in the ice front position of David glacier between 1963 and 2010,
with evidence of melt ponding on the surface of Preiestly glacier 41
4.9 Cumulative changes in ice front position for 10 large glaciers 42
4.10 Cumulative changes in ice front position for 10 small glaciers 43
4.11 Relationship between glacier frontal and elevation 44
4.12 Temperature trends plotted median frontal position change 46
5.1 Casey and Faraday January temperature records 1963-2010 53
5.2 Sea ice and temperature trends plotted against frontal position change 56
5.3 Mean coastal sea ice concentrations (1978-2010) 56
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5.4 Mean difference in sea ice concentrations between 1990-2010
and 1974-1990 57
5.5 Mean annual wind direction at Dumont d’Urville 1974-2010 57
5.6 Antarctic ice shelf thickness change (Pritchard et al., 2012) 58
5.7 Bed topography of the Aurora subglacial basin (Young et al., 2011) 59
5.8 Annual and December – May average SAM index 61
5.9 July surface wind vectors for a negative SAM and the difference in July surface
wind vectors for a SAM positive polarity minus SAM negative polarity (van den
Broeke and Van Lipzig, 2003) 62
6.1 Scatterplots of median frontal position change versus SAM and summer
temperature 64
6.2 2000-2006 and 2006-2010 median frontal position change for DB13 and DB14
versus Dumont d’Urville summer temperature 65
6.3 Number of positive degree days and hours recorded at Casey station 1996-
2007 66
6.4 Glacier elevation change versus glacier width 68
6.5 GRACE surface mass time series for Wilkes Land (Chen et al., 2009) 69

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Statement of Copyright
The copyright of this thesis rests with the author. No quotation from it should be
published without the author's prior written consent and information derived from it
should be acknowledged

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