Future Antarctic Margin Drilling: Developing a Science Program Plan for McMurdo Sound

316 Pages·2003·10.9 MB·English

by  Lori Anderson's Computer

Future Antarctic Margin Drilling:
Developing a Science Program Plan
for McMurdo Sound
Report of a Workshop
Oxford, UK April 5–7, 2001
David Harwood, Laura Lacy and
Richard Levy, editors
ANDRILL Contribution 1

Future Antarctic Margin Drilling:
Developing a Science Program Plan for McMurdo Sound
Report of a Workshop
Oxford, UK April 5–7, 2001
David Harwood, Laura Lacy and Richard Levy, editors
ANDRILL Science Management Office
Department of Geosciences
University of Nebraska–Lincoln
Workshop and Report directed by the ANDRILL Steering Committee (ASC):
Germany―Frank Niessen
Italy―Fabio Florindo
New Zealand―Tim Naish and Gary Wilson (after June 2002)
United Kingdom―Jane Francis and Gary Wilson (prior to June 2002)
United States―David Harwood and Ross Powell
Preparation of this report was funded by: The National Science Foundation
Production and distribution was supported by ASC membership funds
Please cite this report as follows: Harwood, D.M., Lacy, L. and Levy, R.H. (eds.), 2002. Future Antarctic Margin
Drilling: Developing a Science Plan for McMurdo Sound. ANDRILL Science Management Office (SMO)
Contribution 1. University of Nebraska–Lincoln, Lincoln, NE. vi+301 pp.
Please cite sections from the report as: author, year, title of contribution. In: D.M. Harwood, L. Lacy and R.H. Levy
(eds.), Future Antarctic Margin Drilling: Developing a Science Plan for McMurdo Sound. ANDRILL Science
Management Office (SMO) Contribution 1. University of Nebraska–Lincoln, Lincoln, NE.
ISBN: 0-9723550-06
Additional copies of this report and other information regarding ANDRILL are available from:
ANDRILL Science Management Office
University of Nebraska–Lincoln
2255 W Street, Suite 1101
Lincoln, NE 68588-0851
Phone: [phone]
Fax: [phone]
Please visit our website at: http://andrill-server.unl.edu/
Cover photograph taken by D.M. Harwood, 1999. The Cape Roberts Project drilling system operating on the sea-
ice at CRP-3.
Back cover: Satellite image of Southern Victoria Land including the Dry Valley region, McMurdo Sound and
Cenozoic volcanics. Target areas of the McMurdo Sound Portfolio are identified in blue; the black triangles
represent existing drillsites; and the black circles represent potential drillsites as discussed in this report.
Design and layout by Melissa Dunne.
Editors Introduction
This document reflects initial interests, decisions, changes and modifications made to the ANDRILL McMurdo
Sound Portfolio program following the Oxford Workshop (April 2001) and the contributors’ deadline (June 2002).
The purpose of this workshop report is to serve as an introduction to the initial development of a science plan; and to
record the Oxford Workshop proceedings. As with all programs, the ANDRILL McMurdo Sound Portfolio has since
evolved. The following are significant changes or modifications that have been made after June 2002 and were
agreed to by the ANDRILL Steering Committee at its meeting in Asilomar, California, in December 2002, and in
Nice, France, April 2003.
NOTE: The ANDRILL Steering Committee (ASC) has changed its name as of April 2003. It is now
known as the ANDRILL Science Committee (ASC).
The five scientific themes and key questions discussed in the Workshop Report’s Executive Summary have been
modified. Those themes are now:
Theme 1:Glacial transitions/steps and stages in the development of the Antarctic cryosphere
• Late Eocene-Oligocene Oi-1 glaciation
• Oligocene-Miocene Mi-1 glaciation
• Middle-Late Miocene climatic deterioration (Mi4-Mi6 glaciation)
• Late Pliocene global climatic deteroriation
• Mid-Pleistocene climatic transition (MIS 22)
Theme 2: Periods of climatic warmth
• Late Paleocene thermal maximum
• Late Eocene climatic optimum
• Late Oligocene warming?
• Middle Miocene climatic amelioration
• Middle Pliocene warming
• Extreme Quaternary interglacial warm (e.g. MIS 11)
• Mid-Holocene climatic optimum
Theme 3: Orbital and sub-orbital climatic variability, and the role of Antarctic ice cover on
global sea-level and oceanic circulation
• Stability of ice sheets and ice shelves at orbital timescales
• Stability of ice sheets and ice shelves at sub-orbital timescales
• Calibration of the Ocean sediment proxies by correlation with direct records (e.g. calibration of ice volume
and sea-level)
• Interhemispheric comparisons
• Understanding ice sheet “amplification” of the global climate signal (what intervals of past climate were
more sensitive to orbital influences and why?)
• Antarctica’s contribution to Quaternary glacial-interglacial climate cycles
• The role of Ross sea ice and the Ross Ice Shelf on bottom water production
• Rapid climate surprises and extreme events (e.g. D-O climate fluctuations, Younger Dryas and Antarctic
Cold Reversal)
V
Theme 4: Origins and adaptations of polar biota
• Mode and timing of evolution of the polar and sea-ice biota
• Biotic response to warm, cold and extreme environments and events
Theme 5: West Antarctic Rift evolution and uplift of the Transantarctic Mountains
• Mechanism and timing of uplift and basin subsidence
• Volcanic history
• The tectonic boundary conditions of climate change in the Western Ross Sea region
Additionally, the scheduling phases also discussed in the Executive Summary are out dated and have been modified
to the following:
Phase I — Includes several seasons of geophysical/site surveys (2001–) [Reported in the text as three
seasons: 2001–2004]
Phase II — Includes five seasons of drilling, with a 1 year break for a mid-portfolio review (2005–2011),
in different locations in McMurdo Sound [Previously scheduled as four seasons: 2003–2007]
Phase III — Includes six years of data analysis and integration into glaciological, climate and oceanographic
models (2005–2011) [Previously discussed as four years: 2005–2009]
Finally, the Advisory Committee (discussed in Section 7) has been formed and is now identified as the ANDRILL
Science Advisory Panel (ASAP).
For further information or clarification of the themes or scheduling, or for information related to the ASC or ASAP,
please contact either your ANDRILL national representative (which are listed on the title page or can be found in
Section 3 of this Workshop Report) or the ANDRILL Science Management Office (http://andrill-server.unl.edu).
VI
Executive Summary
ANDRILL (ANtarctic DRILLing) is a multinational initiative with the objectives to recover stratigraphic core records
for use in interpreting Antarctica’s climatic, glacial and tectonic history over the past 50 million years and at varying
scales of age resolution (0.1 to 100 thousand years [k.y.]). A key motivation of ANDRILL is that the role of the
Antarctic cryosphere (ice sheets, ice shelves and sea-ice) in the global climate system is complex and poorly known.
Understanding the past history of ice volume variation in Antarctica and associated physical changes in this region is
critical to proper assessment of the global climate system and interaction of ice sheets with the ocean, atmosphere and
biosphere. High-quality sedimentary archives of past ice sheet behavior have become available recently from the
Cape Roberts Project (CRP) (Naish et al., 2001), unfortunately these are too few in number to allow a comprehensive
understanding of Antarctica’s influence on global climate. Through the collection of geological data and their input
into climate and ice sheet models, the ANDRILL Initiative will address this issue. ANDRILL proposes to drill a
portfolio of sites—the McMurdo Sound Portfolio (MSP)—in order to recover critical intervals of Earth’s past climate
history, where the dynamic behavior of ice sheets, ice shelves and sea-ice on Antarctica is thought to have influenced
global ocean and atmospheric circulation and global sea-level elevation. In doing so, we acknowledge that efforts to
understand the role of Antarctic drivers on global climate variability require a fundamental knowledge of Antarctic
cryospheric evolution not only in recent times, which is plainly vital, but also for past times when global temperature
and atmospheric CO were last similar to that which might well be reached by the end of this century.
2
Limited exposures of Cenozoic strata in Antarctica (due to the ice cover), the low number of stratigraphic drillholes
on the continental margin, and the short time that Antarctica has been explored, led geologists to rely on information
derived from lower latitude proxy records. The oxygen isotope record from deep-sea cores, and eustatic changes
inferred from sequence stratigraphic records on passive continental margins have been leading paradigms for the
interpretations regarding Antarctic ice sheet history. However, interpretations based on these proxy records of
glacio-eustasy have little direct confirmation from geologic records in Antarctica, and in numerous cases have led
to conflicting interpretations (Harwood et al., 1991, 1993; Moriwaki et al., 1992; Wilson, 1995; Miller and Mabin,
1998). The ANDRILL initiative will help to remedy this situation with the recovery of new direct records of
Cenozoic strata from locations proximal to the ice sheet that are ideally suited for recording and dating ice sheet
oscillations, and associated oceanic and climatic variations. These will contribute to a better understanding of the
global climate system and clearer linkage between the high and low latitude records.
The basins ANDRILL will target have been the focus of several drilling projects; the most successful of which have
been the Deep Sea Drilling Project (DSDP) (Hayes, Frakes, et al., 1975), Cenozoic Investigations in the Western Ross
Sea (CIROS)-1 (Barrett, 1989; Wilson et al., 1998) and the international Cape Roberts Project (CRP)-1, 2/2A, 3
(Cape Roberts Science Team [CRST], 1998a, b, 1999, 2000; Hambrey, et al., 1998; Barrett, et al., 2001). Despite the
success of these projects, numerous critical intervals which hold many of the keys to understanding climate evolution
in Antarctica, remain uncovered. These missing stratigraphic intervals are to be targeted in the ANDRILL program
(Section 5.0). Completion of the ANDRILL targets will provide an unrivalled sedimentary record spanning some 40
m.y., extending from the pre-glacial conditions in the Eocene, through the onset and growth of temperate ice sheets
with interglacial/glacial cycles in the Oligocene, to the cold ice sheet of today. Efforts are underway to develop an
integrated, high-precision chronostratigraphy for the Antarctic margin and Southern Ocean that will enable linkage of
Antarctic events to global records for comparison and identification of drivers in Earth’s Cenozoic system at key time
intervals. Most important is societal need to recognize and address potential future climate and sea-level changes,
which can be approached through an integrated analysis of geological and historical records from Antarctica within
the framework of climate and glacial model testing.
Stratigraphic drilling by the DSDP played a major role in developing modern theories of Earth processes on many
fronts, but particularly in establishing plate tectonics as a unifying theme of the geosciences. This initiative continues
to enhance our understanding of Earth history through the Ocean Drilling Project (ODP) and the planned Integrated
Ocean Drilling Program (IODP, 2001). Other scientific drilling initiatives planned for the Arctic (Nansen Arctic
Drilling – NAD) and past Antarctic drilling programs (McKelvey, 1991) such as the Dry Valley Drilling Project
(DVDP) (McGinnis, 1981), McMurdo Sound Sediment and Tectonic Studies (MSSTS) (Barrett, 1986), Cenozoic
Investigations in the Western Ross Sea (CIROS) (Barrett, 1989; Wilson et al., 1998) and the recently completed Cape
Roberts Project–– (CRP International Steering Committee, 1994; Barrett and Davey, 1992; Webb and Wilson, 1995;
Davey et al., 2001) will help to bring high-latitude records of Cenozoic climate change into the global picture (Webb,
1990).
i
Fig. 1a: The Cape Roberts Project drilling rig utilizes the coastal fringe of fast-ice as a drilling platform to recover
sedimentary records along the Antarctic margin. Recent developments now enable deep sampling (more than
1500 meters below the sea surface). A standard wireline diamond coring system uses a 5-inch sea-riser to allow
circulation of drilling fluid to give better control of the drill hole with high core quality and recovery (95 to 98%) in
lithified strata. Fig. 1b: Sea-riser styles used from 1975 to 1999 and proposed for ANDRILL sea-ice and ice shelf
platform drilling. The sea-riser is anchored in the sea-floor and tensioned with varied buoyancy methods, or
supported by the ice shelf. (Figures from A. Pyne, Section 6.1)
Determination of the scale and rapidity of changes affecting large ice masses is of vital importance because (i) ice-
volume variations lead to changing sea levels, (ii) ice sheets influence sea-ice distribution, Earth’s albedo, and latitudinal
climatic gradients, and (iii) ice shelves generate cold bottom-water that ventilate the world’s oceans. General circulation
models (GCMs) indicate that the Polar Regions are the most sensitive regions to climatic warming, thus the projected
global rise in temperature of 1.4–5.8˚C by 2010 (Intergovernmental Panel on Climate Change, [IPCC], 2001) is likely to
be even greater in the Antarctic. In order to validate climatic models, we need to look to archives of climatic change
preserved in the ice core record (100,000 year time scale) and in the sedimentary record (10 million year time scale), to
determine the relationship between ice sheet fluctuations and climatic change.
ANDRILL proposes to recover sedimentary cores using a drilling rig positioned on the floating fast-ice, ice shelf, or land
based sites, using and enhancing the technology employed during the CRP (Fig. 1), which during its last season recovered
98% of a 939 m drillcore at the CRP-3 drillsite. Such high rates of core recovery are in contrast to that of ODP and DSDP
(Section 5.0), which are unable to operate efficiently on the Antarctic margin with recovery rates between 6 to 60%. The
McMurdo Sound Portfolio (MSP) is the first of a series of portfolios that will be developed to address key questions
related to Antarctic geology and global climate issues using this technology. Cruise objectives of DSDP and ODP legs
into Antarctic waters highlight science objectives in the Antarctic arena, but have largely been unable to answer key
questions because of the poor core recovery inherent in drilling glacigene sediments using current ODP technology.
The development of a better understanding of Antarctic climate and glacial history and this region’s influence on
global climate are critical to the science that will result from the new IODP, 2001. ANDRILL will complement and
expand the ability for IODP to succeed in its mission. The Shallow Drilling (SHALDRIL) and ANDRILL projects
are complementary, with similar goals, but able to reach different stratigraphic targets around the Antarctic margin.
A proposed Scientific Committee on Antarctica Research (SCAR) initiative, ACE (Antarctic Climate Evolution
[http://www.ace.scar.org//]), will provide an important vehicle to integrate the information gained from these
drilling projects and expand their value as data are incorporated into glacial and climate models. The overlapping
membership in steering committees that direct these initiatives will help integrate objectives and results obtained
from these geological tools. The science program presented in the following chapters continues to develop. It is
in line with scientific themes and objectives highlighted in numerous recent workshops and international planning
documents (for example: Webb and Wilson, 1995; Webb and Cooper, 1999; Barker et al., 1998; Kristoffersen et
al., 2000; Florindo and Cooper, 2001).
This report summarizes the results of the first ANDRILL Workshop, held at Oxford University, UK, from April 5 to
7, 2001. The workshop was attended by thirty-nine scientists and technical experts from seven nations — Australia,
ii
Germany, Japan, New Zealand, United Kingdom and United States. The aim of the Workshop was to develop a
science plan and organizational structure to best meet the above scientific and societal needs. An ANDRILL consortium
has been established, comprising five countries – Germany, Italy, New Zealand, United Kingdom and United States.
Other interested nations are welcome to join this initiative.
This Workshop brought together an international team of interested scientists and technical advisors and called for the
organization of national workshops and scientific groups, which at the time of this printing have all been completed.
The ANDRILL Initiative evolved considerably over the past 2 years since the completion of the final CRP Workshop
in Columbus, Ohio (September, 2000), and will continue to evolve and mature. This document reflects ideas and
concepts developed at the Oxford Workshop, at subsequent national workshops, and through the efforts of the ANDRILL
International Steering Committee (ASC).
Five scientific themes and key questions will be ANDRILL’s focus in an integrated three-phase approach
involving geophysical surveys, stratigraphic drilling, and climate and glacial modeling.
Theme I — Thresholds and stages in the development of the cryosphere
• Pre-glacial, ‘greenhouse’ Antarctica
• Oligocene transition to the ‘icehouse’
• Shift of the dynamic ice sheet into the deep-freeze
Theme II — Climatic optima and ice sheet stability
• Inter-hemispheric linkages
• Testing the proxy records of Quaternary variation
• Pliocene, marine oxygen isotope stage 11 (and other recent periods of extreme warmth)
Theme III — Ice sheet modulation of global climate and sea-level
• Influence of ice shelves, sea-ice on global systems
• Effect of abrupt changes in the Ross Ice Shelf (RIS) on Antarctic bottom-water (AABW) production
• High-resolution records of Neogene Milankovitch cyclicity in ice sheet and sea-level
Theme IV — Origins and adaptations of polar biota
• Mode and timing of the evolution of the polar and sea-ice biota
• Biotic response to warm, cold and extreme environments and events
Theme V — West Antarctic Rift (WAR) and uplift of the Transantarctic Mountains (TAM)
• Mechanism, timing, flexural response to volcanic loading
• Influence of glacial, tectonic, and volcanic processes in sediment accumulation
• Relationship of TAM uplift and climate model boundary condition
• Phase I — Includes three seasons of geophysical surveys (2001–2004) to document basin extent, architecture
and to correlate target drilling areas to known drillcores. A 2-year geophysical survey program including
gravity and magnetic surveys, and seismic acquisition from the sea-ice and ice shelf is already underway
through collaborative efforts of all ANDRILL member nations.
• Phase II — Includes four seasons of drilling (2004–2008) in different locations in McMurdo Sound (back
cover of this volume) to obtain high-resolution, seismically-linked, chronologically well-constrained
stratigraphic records from the Antarctic margin to address the above scientific themes and key questions.
Geological targets in these four areas focus on several key time intervals that have not yet been recovered
from the Antarctic region (Section 5.0). Details of the four target regions and specific scientific objectives and
ages are presented below.
• Phase III — Includes four years of data analysis and integration into glaciological, climate and oceanographic
models (2005–2009) to determine global links and the role of the Antarctic cryosphere in global environmental
change. A strength of ANDRILL will be the follow-up integration of glaciological and climate modeling with
acquisition of drillcore data. A new initiative to be proposed for approval by SCAR is the ACE Working
Group, whose charge will be to address “Antarctic Climate Evolution” through the integration of geological
data with model data. ANDRILL will provide vital new information to this objective of model testing.
iii
This document includes statements from more than 150 international geoscientists who have expressed an interest in
generating new data regarding the tectonic, climate and glacial history of the southern high latitudes. Antarctica
represents one of the last frontiers on this planet, and there is much we still do not understand regarding the past
history and future stability of the Antarctic Ice Sheet, which drilling can help the scientific community resolve (Denton
et al., 1991; Webb and Harwood, 1992; Wilson 1995; Barrett, 1996, 1999; Miller and Mabin, 1998; Barker, et al.,
1998). The international collaboration and close scholarly relationships with scientists from many nations and of
different scientific expertise is invigorating, productive, and rewarding.
We should work to integrate ANDRILL, SHALDRIL, ACE, IMAGES, ANTEC, PAGES, and other initiatives into a
focused research program to address questions central to all of them. ANDRILL will develop a glacial and climate
history for the TAM area of Western Ross Sea (WRS), building on existing records to construct a robust
chronostratigraphic framework. Coincident work by SHALDRIL could target key areas on the other side of Antarctica
to feed the climate and glacial models with data from sensitive areas identified by the models. Besides the McMurdo
Sound area, the region with the best-developed Cenozoic glacial record is the Prydz Bay and Lambert Glacier area.
Seismic data, excellent on-land exposures in the four Cenozoic formations of the Pagodroma Group and the southern
end of a latitudinal transect of ODP holes, makes this a significant region for future targeted effort (Hambrey and
McKelvey, 2000 a,b). The Lambert Glacier and Amery Ice Shelf area drains a large portion of the East Antarctic Ice
Sheet (EAIS), including the and Gamburtsev Subglacial Mountains, and is a critically sensitive region for the climate
models. The Antarctic community will advance science further with a coordinated plan to pool resources to a common
target, or set of targets that will maximize the impact on model results. The decisions to incorporate modeling (1) into
the later stages of Antarctic Offshore Acoustic Stratigraphy (ANTOSTRAT) (Kristoffersen et al., 2000), (2) as the
third phase of ANDRILL, and (3) as a central focus of ACE, are all positive forward steps.
Future discoveries, unanticipated and fortuitous surprises, are a positive reality in Antarctic science, due to the limited
knowledge of this region. Current paradigms and our understanding must remain flexible and adaptable. We have
come far in generating knowledge about the southern continent; many of the questions we have been asking are now
more clearly defined and our hypotheses are more mature. Testing these and developing better tools for application in
this still remote area of Earth will be challenging, exciting and educational. Rewards come in the expansion of
scientific thought, in the complex, cross disciplinary discussions and in open international collaboration. To date,
five member nations have subscribed to ANDRILL, and membership is open to any interested Antarctic Treaty
nation. The scientific results represent only one of the outcomes from this large endeavor; ANDRILL also provides
a vehicle to educate new scientists, to inform the public about the process and merits of scientific research, and to
provide information that will bear on societal need to plan for the future. The ASC recognizes the value in public
outreach and education at all levels, and will endorse efforts to maximize the opportunities that ANDRILL can
provide in this direction.
David M. Harwood on behalf of the ANDRILL Steering Committee
Fabio Florindo, Italy
Jane Francis, UK
David Harwood, USA
Tim Naish, NZ
Frank Niessen, GER
Ross Powell, USA
Gary Wilson, NZ/UK
iv