ANTARCTIC ICE-MARGIN EVOLUTION WORKSHOP, HOBART, TASMANIA, AUSTRALIA, JULY 6-11, 1997

ANTARCTIC ICE-MARGIN EVOLUTION WORKSHOP, HOBART, TASMANIA, AUSTRALIA, JULY 6-11, 1997

SUMMARY

A coordinated SCAR-GLOCHANT (Global Change and the Antarctic) and PAGES (Past Global Changes) initiative on circumpolar paleoenvironmental research detailing the last 250 ka, is designed to provide a better understanding of present and future variability in the Antarctic. The initiative is termed ANTIME, that is, ALate Quaternary Sedimentary Record of Antarctic Ice Margin Evolution@. This grant provided travel support for eight U.S. scientists to attend the first ANTIME workshop in Hobart, Tasmania, held from 6-11 July, 1997. There were a total of 65 participants from Australia, Germany, Italy, Japan, Spain, Sweden, Russia, UK and USA. The principal results of the workshop were to: define the work that needs to be done and establish a draft science and implementation plan for future research priorities and opportunities; initiate future scientific workshops and publications; and initiate future collaborative and cooperative research among individuals and national programs to achieve ANTIME objectives. Each of these goals has been met.

INTRODUCTION

The Antarctic sedimentary record has already yielded high‑resolution information on paleoenvironmental and paleoclimatic changes, particularly on ice marginal and outlet glacier fluctuations and in lacustrine and marine ecology and biogeochemistry. A coordinated SCAR-GLOCHANT (Global Change and the Antarctic) and PAGES (Past Global Changes) initiative on circumpolar paleoenvironmental research detailing the last 250 ka, will provide a solid basis for the understanding of present and future variability in the Antarctic. The coordinated SCAR-PAGES initiative termed ANTIME (Antarctic Ice Margin Evolution) will be focused in two streams: Stream 1 (last 20 ka) focusses on the last deglaciation and interglacial environmental, climatic, and ice‑sheet variability. Stream 2 (last 250 ka) will focus on the environmental, climatic, and ice‑sheet response to glacial‑interglacial cycles.

FIRST ANTIME WORKSHOP

The first ANTIME workshop on the Late Quaternary sedimentary record of Antarctic ice margin evolution was held from 6-11 July in Hobart, in parallel with the SCAR-ANTOSTRAT (Antarctic Offshore Stratigraphy) workshop. There were 65 participants from Australia, USA, UK, Italy, Spain, Japan, Sweden, Germany and Russia. The participants included representatives of PAGES, IMAGES, INQUA and IASC. An abstract volume was published prior to the workshop. In summary, the workshop addressed the current status of knowledge and developed the following key scientific themes on which the project will concentrate:

< The extent, timing, and regional differences of the Last Glacial Maximum in Antarctica;

< What rapid or episodic events occurred during the Late Quaternary?

< What are the key forcings and feedbacks that influence the retreat and readvance of the Antarctic ice sheet?

< What changes have occurred to the ice shelves and outlet glaciers during the Holocene?

< Technology coordination; and,

< Correlation of Late Quaternary Antarctic environmental history and deep ocean sedimentary records.

IMPLEMENTATION PLAN AND RESEARCH PROTOCOL

Plan Outline

Priority Research Topics

1. Paleogeography of glacial extent and volume during the last glacial cycle

a) What do we know about extent, fluctuations in these regions?

The big problem areas Ross ice sheet and shelf

Weddell ice sheet and Filchner-Ronne Ice shelf

Antarctic Peninsula

East Antarctica

b) Lack of a detailed coupled offshore/onshore chronology

c) Ice stream and shelf trough bathymetry, ice sheet and shelf bank bathymetry

d) Sea ice zone and deep sea cores

2. Style and mode of late glacial retreat

a) Establishing a sedimentary facies and paleoenvironmental sequence for retreat

b) Conditions controlling the retreat (ice dynamics, sea-level, sediment dynamics, and climate/ocean forcings.

3. High resolution paleoenvironmental and paleoclimatic records for the Holocene (particularly Mid-late Holocene) [Workshop focus 4]

a) Lacustrine

b) Shelf

c) Coastal

d) Fjord

e) Coupled ice core and sediment records

Scientific Strategies for Fieldwork and Data Synthesis

1. Regional site selections (transect philosophy and circum-Antarctic coverage)

2. Marine strategies [Workshop focus 3]

3. Coastal strategies [Workshop focus 1]

4. Lacustrine strategies

5. Glacial basin strategies

6. Chronological methods [Workshop focus 2]

Proposed Implementation Outputs

Maps, workshop reports, data management and exchange, scientific papers and

reports.

Three working groups have been formed to facilitate this process. The priority research topics are:

< Paleogeography of glacial extent and volume during the last glacial cycle;

< Style and mode of late glacial retreat under climate warming and rising sea-level;

< High to medium resolution event stratigraphy for the Holocene, from sedimentary investigations in lake, coastal, fjord, and shelf sequences; together with the high resolution ice core records from coastal ice domes.

It was agreed that this research should be completed for 12 priority regions, which characterized the range of ice morphologies and climatologies that exist in the circum-Antarctic. These priority regions will also be used to plan future fieldwork and data correlation, and involve the linking of onshore glacial and coastal projects with marine

projects on the continental shelf and slope, together with deep ocean coring projects administered through the IMAGES program. Extensive data sets have already been collected in many of these regions, and future research is planned with national and/or international logistic support for each of these regions, over the period 1998 to 2003.

Scientific strategies for fieldwork and data synthesis are currently being developed by the SSC and from the wide scientific community for ; regional site selection, marine, coastal, lacustrine, glacial basin sedimentary records, and modeling. The strategies will be further developed through small workshops. A strong linkage between the Southern Ocean drilling programs of IMAGES was developed, to extend the sedimentary record from the polar front to the Antarctic margin.

SCIENTIFIC ADVISORY COMMITTEE

An advisory committee was selected for the ANTIME program at the Hobart workshop, such that all national programs and Antarctic sub-regions were represented. The nominated advisory committee is as follows: I. Goodwin (Australia; Co-chair and program coordinator), R. Powell (USA; Co-chair), J. Anderson (USA - WAIS rep.), M. Bentley (UK), P. Berkman (USA), M. Canals (Spain), E. Domack (USA), R. Gersonde (Germany - ODP/IMAGES rep., Atlantic sector), P. Harris (Australia), K. Hirakawa (Japan), C. Hjort (Sweden), W. Howard (Australia - ODP/IMAGES rep., Indian and Pacific sectors), C. Pudsey (UK - ODP rep., Antarctic Peninsula sector), M. Taviani (Italy).

SPECIAL ISSUE OF ANTARCTIC SCIENCE

An outgrowth of the ANTIME workshop was the development of the projects first publication. An ANTIME Special Issue of Antarctic Science will be published in September, 1998. The issue is co-edited Ian Goodwin and Carol Pudsey, and contains 10 papers spanning onshore and offshore studies which were developed from presentations and discussions at the Hobart workshop. A special budget request was made last July to the SCAR Executive for 4,000 pounds Sterling, for page charges.

WORKSHOP PLANS 1998 & 1999

A the workshop, future workshops were planned and the first two have been initiated. The Coastal Working Group are planning to hold a workshop on; " Circum-Antarctic coastal environmental and sea-level variability during the Late Quaternary", in Japan, from September 16-21, 1998. The workshop will be sponsored by the Japanese National Institute of Polar Research (NIPR), GLOCHANT, the Japanese Polar Research Association (JPRA), the Japanese Society for the Promotion of Science (JSPS) and the US National Science Foundation (NSF). The workshop will be held at an NIPR facility at Lake Kawaguchiko, near Mount Fuji. The organizers are K. Hirakawa, NIPR, P. Berkman, Byrd Polar Research Center, Ohio State University, USA, and I. Goodwin. PAGES and JPRA have allocated $US 5,000 each for the workshop.

An Antarctic radiocarbon workshop to address problems of radiocarbon ¹⁴C dating and carbon systematics in Antarctic and the Southern Ocean" is in the preliminary planning stages for May, 1999 in the USA. The workshop will be organized by Eugene Domack, Hamilton College, USA, together with members of the working group on Late Quaternary Antarctic geochronology. PAGES have allocated US $5,000 for the workshop.

DATA MANAGEMENT

Data management is a key issue for the ANTIME program, and it is anticipated that the main interpretive data sets will be coordinated through the Hobart office and submitted to the World Data Center for Paleoclimatology, Boulder. Following discussions at the workshop, we are seeking advice on data management from the chair of the Joint Committee on Antarctic Data Management, and the PAGES data management coordinators.

ANTIME CRUISES AND ONSHORE FIELDWORK

Collaborative field work was also discussed at the workshop and the following are on-going results of the plans developed. In the coming 1998/99 season, the Italian-Australian WEGA expedition will be conducting onshore and offshore ANTIME research along the coasts and adjacent continental shelf off eastern Wilkes Land, Terre Adelie and George V Land. The work will involve seismic surveys, shelf and lake sediment coring, surveys of Holocene coastal environments and the glacial geology of the shelf, including the Mertz-Ninnis Glacier troughs and the East Antarctic ice sheet margins. Holocene paleoenvironmental research is being conducted by Australian researchers in the Bunger Hills, Vestfold Hills and Prince Charles Mountains, and ANTIME related cruises were conducted along the Vincennes Bay, Prydz Bay and MacRobertson shelf regions in 1996 and 1997.

Japanese research on JARE will be continuing in the Lutzow-Holm Bay region of East Antarctica. UK research was focused on attempting to determine the extent of the LGM and timing of deglaciation from the maximum in the southern Antarctic Peninsula in eastern Ellsworth Land, southern Palmer Land. Some reconnaissance work along George VI Sound was carried out to investigate the Holocene record of glacier and ice shelf variations. US research ANTIME fieldwork since 1996 has included the LM Gould Cruise 1998 to Andvord Bay and Llalamand Fjord, and the recently completed cruise to Ross Sea and offshore of Northern Victoria Land on NB Palmer (Jan 15-Feb

20, 1998). Another US cruise to the Amundsen Sea and Bellingshausen Sea shelf is planned for 1998/99. Spanish ANTIME research including both onshore and offshore surveys, has been focused on the South Shetland Islands, Bransfield Strait, Pacific margin of Western Antarctica, the Bransfield Basin (Univ. Barcelona and Univ. Autonoma Madrid and BAS), and James Ross Island.

ANTIME ACTIVITIES RELATED TO THE OCEAN DRILLING PROGRAM (ODP)

Leg 178 Antarctic Peninsula

Leg 178 completed two sites in Palmer Deep, Antarctic Peninsula in March of 1998. These are sites 1098 and 1099. Ultra-high resolution stratrigraphy of site 1098 will address climate change issues at decadal to millennial time scales for the entire Holocene (a 48 m section). The cores will also provide a framework for geochronologic studies related to ¹⁴C reservoir changes, secular paleomagnetic variation, and paleoproductivity events. Site 1099 recovered 108 m of section that likely predates the Last Glacial Maximum and will therefore provide paleoceanographic and ice margin

information during most of the Wisconsinan (O-isotope stages 4-2) for the Antarctic continental shelf, this is an exciting new data set. Other sites were drilled on the continental rise on large sediment drifts. These provided good resolution of glacial-interglacial cycles back through the Pliocene and will certainly help resolve glacial cyclicity patterns within the last 200,000 years. A good paleomagnetic record and

biostratigraphy is already available from these sites.

Leg 188 Proposed for Prydz Bay

A proposal has been "penciled-in" for drilling in early 2000. Objectives of this series of sites lie at the end of the Prydz Channel, the Prydz Trough Mouth Fan. Leg 188 is hoped to resolve glacial-interglacial cyclicity within the sequence to provide a framework for understanding the timing of Antarctic glacials as they relate to sea level changes brought about by northern hemisphere glaciation. An additional site was proposed as an addendum for the inner shelf where an ultra-high resolution record of

Holocene climate change may be obtained and therefore help to address (with Palmer Deep) the circum-polar changes in climate over short time scales.

Initiating a circum-Antarctic reconstruction of paleoclimate, paleoenvironment and ice sheet paleogeography throughout the last glacial cycle the ANTIME program has determined priority field research locations and is organizing national and multinational field projects in each of these regions a database of high resolution proxy climate and environmental information is being collated from lake, coastal, fjord, and shelf sedimentary sequences which cover the last 10,000 years. ANTIME is also driving a project with scientists from the ice coring and deep sea sediment communities to correlate these large data sets and establish the climate forcing mechanisms and environmental responses.

ODP proposals for Antarctic Holocene targets

It has been suggested that Holocene targets similar to Palmer Deep be considered as sites of opportunity for each of the four outstanding drilling proposals for ODP. It was further suggested that ANTIME develop a rationale to evaluate the scientific merits of each of these potential targets. A draft table of such sites has been established. The details of each of these rankings will be included in an addendum for each of the basins that will be sent to the appropriate lead proponent of the proposals.

TABLE I: Rankings of Holocene targets for outstanding ODP-Antarctic drilling proposals

Proposed Basin Site Survey Resolution Chronology

Region & Process Linkages

Prydz Bay Nielsen Basin Very Good Very Good Good

Iceberg Alley Good Excellent Good

Wilkes Land Mertz-Ninnis Poor Very Good Fair

Trough

D'Urville Trough Poor Good Good

Ross Sea Granite Harbor Excellent Very Good Excellent

Weddell Sea ---------------------------------- no information----------------------------------------

Notes:

1. Site Survey = Availability of 3.5 kHz type seismic profiles, sediment cores, site bathymetry.

2. Resolution = accumulation rates (high rates are better), sediment thickness (complete or thick sequences of Holocene are better), presence and continuity of laminae based upon existing cores (continuous laminae are more desirable for potential of marine varve chronology).