SciBlogs

ANZICE Part 5: Policy Interface Matthew Wood Jul 07

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homeThe ANZICE program is certainly producing some intriguing results when viewed from a purely scientific perspective. But the serious implications of this research for the future of our environment and society give this work a pertinence beyond just the scientific community. Preliminary results are strongly suggesting that we have no time to lose in making significant changes towards a lower carbon economy.

Sean Weaver is an Honorary Research Associate in the School of Geography, Environment and Earth Sciences at Victoria University and now runs Carbon Partnership Ltd, a company that specialises in innovative climate change solutions through carbon financing, waste reduction and alternative energy sources. Sean is working towards synthesising the scientific results of ANZICE, interpreting the policy implications of those results and translating them into accessible and policy-relevant language.

CP_Logo_Black_shadowAt an international level, this process of translation is greatly facilitated by the Intergovernmental Panel on Climate Change. The IPCC seeks to achieve consensus on climate change issues, and to provide reliable information for the international policy community, based on rigorous scientific research. However, the IPCC’s effectiveness for informing policy has been systematically undermined by lobby groups, and their receptive audiences in government, bent on maintaining the status quo. The 5th Assessment Report of the IPCC is due in 2013 and the results of ANZICE will be directly contributing to this compendium through Working Group I (and to a lesser extent Working Group II).

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In a world dominated by the quest for perpetual ‘growth’ one quarterly statement at a time, one of the biggest challenges for environmental planning is to convince government and business to invest in distant sustainable futures: to step back and perceive the value of the things that we currently take for granted (our inshore fisheries and our glacier-fed central South Island hydroelectric lakes are examples particularly relevant to ANZICE). Strategic management of our environment and resources is essential for safeguarding the quality of life of future generations. As the Greek proverb so eloquently puts it, “a society grows great when old men plant trees whose shade they know they shall never sit in”.

The climate is still a poorly understood system. But this knowledge gap needs to be viewed as a challenge for, not a failure of, modern science, and public research funding needs to be targeted accordingly. Applied climate science initiatives like ANZICE can help clear up common misconceptions surrounding the complexities of the climate system, show us where our efforts for change will be most effective, and give a quantitative sense of just how much we stand to lose through complacency.

To download the podcast for your iPod, simply search and subscribe for free through the iTunes Store. For playback on other portable media devices please download from the Journeys to the Ice homepage. Otherwise you can listen straight away by using the player below.

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Photo and logo (c) Carbon Partnership Ltd.

ANZICE Part 4: Climate Models Matthew Wood Jun 22

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PrintSuspended by string from the ceiling of my tween-years bedroom, the wooden skeletons of prehistoric reptiles jostled for space among enamel-coated Harrier jets and Hellcats, sculpted in miniature from cast plastic and balsa. And I wonder why I never had a girlfriend back then? The point is I loved models.

I clearly remember being thrilled by the way that, from my own efforts, the essence of an entire railway system and its environs could be so elegantly realised in 00 gauge. The more I knew about real train systems, and the better honed my skills of recreation became, the more life-like and satisfying were the results. In this latest episode of the podcast we’ll take a look at some models that are, at once, exactly the same as, and utterly different to, those of my childhood fancy.

Modeling has always been a vital part of science’s toolbox — physical models such as flumes or wave pools can simulate the behaviour of larger water masses, for example — but increasingly, scientific modelers are harnessing the power of super computers for virtual simulations of natural systems. Simulations are obviously the only option for predictive studies of future change, but the validity of the model in use has to be shown by its ability to recreate known situations of the present or past. Regardless of how impressive the processing power of computers becomes, scientific modeling will always rely on a foundation of rigorous empirical data collection.

The Climate Models research stream of ANZICE is figuring out at what rate polar ice shelves and the temperate glaciers of New Zealand’s Southern Alps are likely to respond to predicted short- and long-term changes in climate. Their modeling has already successfully recreated the recent and highly publicised collapses of Antarctic ice shelves, and predicts the loss of all Arctic ice shelves by 2100. An energy balance model (EBM) for the Southern Alps has helped improve the understanding of the relationship between our glaciers and the local climate system.

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New Zealand’s glaciers are proving to be highly sensitive indicators of changing atmospheric circulation, particularly the large debris-free glaciers of the West Coast such as Franz Josef. While the Southern Alps have lost 30-48% of their ice mass since the mid-19th century, many glaciers have shown an anomalous readvance since the early 1980s. This appears to be related to an increase in, and shift of, Tasman Sea anticyclones that have increased southerly airflow and led to a slight cooling of the high mountain catchments.

The long-term goal is to couple the EBM to a model that simulates the dynamics of ice sheets, thus allowing the detailed simulation of past ice extents — tying in closely with the moraine mapping and dating efforts of GNS Science’s Central South Island Glacial Geomorphology project. This powerful computer model will be able to provide quantitative paleoclimate (past temperature and precipitation) estimates for the region based on geological evidence. Bear in mind that the scientists behind these models are not stuck in some windowless room staring at a screen through square eyes 24/7. Their models are completely reliant on real-world data: weeks of intensive fieldwork are required each year, monitoring weather stations and collecting continuous measurements of mass balance change and stream discharge.

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Hailing from Melbourne, Andrew Mackintosh has a career in glaciology that has so far taken him from the Greenland ice sheet to Tasmania, from the volcanic ice fields of Iceland to East Antarctica. Now based at the Antarctic Research Centre, Andrew works closely with Brian Anderson and leads the Climate Models team of ANZICE, including 6 post-graduate students. By progressing to the second round of this year’s Marsden funding applications, the research group’s coupled energy balance-ice sheet opus is still in the running towards becoming New Zealand’s next top model.

To download the podcast for your iPod, simply search and subscribe for free through the iTunes Store. For playback on other portable media devices please download from the Journeys to the Ice homepage. Otherwise you can listen straight away by using the player below.

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Photo (c) Matthew Wood 2008

ANZICE Part 3: Southern Ocean – New Zealand Responses Matthew Wood Jun 05

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Sediment core 1New Zealand is a geographically lonely place. It is the only major landmass between the tropics and Antarctica at these longitudes, and shares the southern mid-latitudes with only Patagonia and Tasmania. As such, it is a fantastic natural laboratory for investigating oceanic and atmospheric change in the southern hemisphere.

Our country is perpetually being ground down by the elements in response to rapid uplift. Terrigenous sediment makes its way down river systems to be distributed far into the deep ocean, forming thick, continuous sedimentary sequences. While the sediment itself can appear outwardly unadorned, the real story is locked within the calcareous remains of plankton that have lived their short time in our seas and subsequently dropped to the seafloor to be entombed within the layers of mud. The geochemistry of their tiny shells can be used as proxy data for ocean temperature and salinity, and to assess changes in ocean currents over time.

Phytoplankton are autotrophs and thus live in surface waters of the ocean. When conditions are right — when the waters are sufficiently warm, well-lit and rich in nutrients — massive algal blooms may be initiated, often forming along major ocean fronts. These populations of microscopic plants may be so extensive as to be easily visible from space. Such blooms are thought to flourish during warm periods — evidence of an extreme case being the chalk deposits now exposed in the famous white cliffs of Dover, formed during the super hothouse world of the late Mesozoic. Such blooms appear to be increasing off New Zealand today: can this be attributed to global warming?

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This is one of the questions that the Southern Ocean — New Zealand Responses research stream of ANZICE is currently attempting to answer. Whether these blooms are driven primarily by ocean temperature, or by the amount of incoming solar radiation, is unknown. Answering this question is important because phytoplankton are the base of the marine food chain and so any changes at this level will propagate through the whole system. They also provide their own feedback into the climate system by producing atmospheric acids that act as condensation nuclei for clouds. The calcium carbonate tests of plankton also comprise a significant carbon sink in the deep ocean, particularly so in the Southern Ocean during glacial periods, as outlined in a very recent paper.

Along with marine microfossils in these seafloor sediments are the robust pollen grains of land plants, transported to their marine resting place by the vigours of water and wind. By coring these sediments from oceanographic research vessels, ARC scientists are able to identify changes in vegetation cover on land in response to climate change. This wealth of information is made even more valuable by the logistical challenges of sampling it. This work would not be possible without collaboration with GNS Science, NIWA and research groups abroad.

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A recently initiated study by the group is a classic case of uniformitarianism; the geological premise that the present is the key to the past. Beneath the central South Island glacial lakes are hundreds of metres of finely layered silts. It is not known what this layering represents and so it is prudent to first understand the modern day processes in these lakes before starting to make inferences about the past. Instruments have been deployed to measure what happens on a monthly basis in terms of water and sediment flux through the Lake Ohau system.

Gavin Dunbar returned to the Antarctic Research Centre in 2005 after working at the Australian National University (ANU), where he was interested in the climate history of the Western Pacific as shown in coral and speleothem geochemical records. Gavin now leads the Southern Ocean — New Zealand Responses group of ANZICE and supervises a number of post-graduate students who he has seen become experts in their own fields.

To download the podcast for your iPod, simply search and subscribe for free through the iTunes Store. For playback on other portable media devices please download from the Journeys to the Ice homepage. Otherwise you can listen straight away by using the player below.

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Satellite image from SeaWIFS. Photo (c) Matthew Wood 2006

ANZICE Part 2: Antarctic Climate Drivers Matthew Wood May 24

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To ask the question, ’How will Antarctica respond to a warmer world?’ is similar to pondering, ’What was the weather like in the United States last century?’ In both cases there are multiple layers of complexity — from persistent regional disparities to variability on a range of timescales — yet this is a question being tackled by Earth scientists around the world, including those in the Antarctic Climate Drivers cluster of ANZICE at the Antarctic Research Centre.

Originally from Bavaria, Nancy Bertler came to the ARC in 1999 to undertake a PhD in ice core research. Now, little more than a decade later, she has 10 Antarctic field seasons under her belt and leads the Antarctic Climate Drivers research stream of ANZICE. She also represents New Zealand in the International Trans-Antarctic Scientific Expedition (ITASE) and her work unites Victoria University and GNS Science through the Joint Antarctic Research Institute.

Ice Core

In this episode of Journeys to the Ice, Dr. Bertler points out the double-importance of Antarctica in climate change research, namely, its role as an archive of past climate records, and as an agent of dramatic and global environmental change in response to current and future anthropogenic-induced global warming. Nancy’s research is aimed at making sense of a small part of the large range of variability in Antarctic climate. By analysing climate proxies preserved in high resolution ice cores from relatively small glaciers on the Victoria Land coast (see this previous posting/episode for further information), Nancy’s work has shown that episodic cooling in this part of Antarctica is caused by the shifting pathways of Southern Ocean air masses; a climate phenomenon now known to be driven by the El Niño Southern Oscillation.

Beneath the myriad of spatially- and temporally-localised intricacies in Antarctic climate however, are some undeniable and ubiquitous trends. A landmark study published last year by a research group led by Eric Steig of the University of Washington, found that the 50-year record of measurements from Antarctic weather stations (complemented by 30 years of satellite data) shows an Antarctic-wide warming trend, including a particularly marked warming in West Antarctica and the Ross Sea.

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This finding, along with the historically unprecedented collapse of numerous small Antarctic ice shelves in recent decades and the discovery that the Southern Ocean is warming to depth, raises major concern about the stability of the Ross Ice Shelf, another focus of the Antarctic Climate Drivers group. The Ross Ice Shelf, the largest on Earth, separates the West Antarctic Ice Sheet, which is largely grounded below sea level, from the open ocean. The loss of this floating natural barrier would put West Antarctica’s grounded ice in grave danger of melting and/or detaching, either of which would raise global sea level by up to six metres. By collecting a 780 metre-long ice core from Roosevelt Island, near the present day seaward edge of the ice shelf, Nancy’s team hopes to reconstruct the retreat of the ice shelf during recent warm extremes and identify the threshold temperatures for complete collapse.

To download the podcast for your iPod, simply search and subscribe for free through the iTunes Store. For playback on other portable media devices please download from the Journeys to the Ice homepage. Otherwise you can listen straight away by clicking on the link below.

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Photo (c) Nancy Bertler

ANZICE Part 1: An Overview Matthew Wood May 13

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It is ironic that a science initiative called ANZICE should be concerned with investigating times in our geological past when there was relatively little of the cold, slippery stuff around.

The Antarctica — New Zealand Interglacial Climate Extremes program, currently underway at the Antarctic Research Centre, is aimed at better understanding the relationships between Antarctica, New Zealand and global climate. By reconstructing environmental responses to episodes of past warmth, regional climate models can be developed. Peak warm periods (interglacials) such as Marine Isotope Stage 5e (~125,000 years ago), when atmospheric and surface ocean temperatures were up to 3°C warmer than today, are important analogs for the climatic conditions predicted for the next century by the IPCC.

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The general public and media do not necessarily appreciate the complexities of this science and so it needs to be translated into an easily digestible form. It is particularly important to be able to communicate the results to those who will ultimately make the decisions about how we manage our environment in the future. By understanding past climate, ANZICE will be well-placed to advise policy makers on what changes to expect in the New Zealand — Antarctic region in a warmer world of the future.

ANZICE comprises three research streams:

  • Antarctic Climate Drivers
  • Southern Ocean — New Zealand Responses
  • Climate Modeling

High-resolution ice cores from Antarctic coastal glacier sites are expected to document the Holocene Climatic Optimum by atmospheric gases, isotopes of water, major and trace elements, dust, and various compounds. Marine plankton, such as foraminifera, preserved in seafloor sediments provide valuable climate-related elemental and isotopic information in their sand-sized shells. The environmental response of terrestrial New Zealand can be gauged by studying lake sediments. These disparate environmental data, combined with the dynamics of temperate glaciers here in New Zealand, are used to generate empirical and computer-based climate models. These models are currently being fine-tuned, but are already proving to be extremely powerful scientific tools.

The program is funded by the Foundation for Research Science and Technology, and is closely tied to the FRST-funded Global Change Through Time programme at GNS Science and the ice core gas analysis group at NIWA. Collaboration within the research centre, and between the ARC and other science institutions, maintains scientific rigour and allows open-access to facilities and expertise.

Professor Lionel Carter leads the ANZICE team.

To download the podcast for your iPod, simply search and subscribe for free through the iTunes Store. For playback on other portable media devices please download from the Journeys to the Ice homepage. Otherwise you can listen straight away by clicking on the link below.

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Sugar, You Ain’t So Sweet Matthew Wood Apr 26

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’Sugar? No problem! Ethanol? No problem!’ the Padre assures his audience. ’It’s the model…’ the model for biofuel production in Brazil that he’s here to denounce.

Tiago Thorlby, a Scottish ex-pat priest, belongs to an ecumenical church organisation called Comissão Pastoral da Terra, CPT (The Land Pastoral Commission) and for 25 years has worked with rural Brazilians marginalised by the monocultive agribusiness of sugar cane.

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Kay Weir of the Pacific Institute for Resource Management and editor of Pacific Ecologist, and Peter Barrett of Victoria University’s Climate Change Research Institute (and until recently the director of the Antarctic Research Centre), hosted Padre Thorlby in Wellington last week, where he spread the word about New Zealand’s (and particularly Wellington’s) importing of unsustainable and unethical Brazilian-made biofuels. He brought with him some arresting footage, and countless personal anecdotes, of the plight of sugar cane workers in Pernambuco, where manual labour is commonly tantamount to slavery.

When Padre Thorlby first arrived in Brazil in the 1960s, 70% of the population lived and worked on the land. Today, that figure has dropped to just 17%; in part a response to a latifundiary land use system, which includes sugar cane estates of up to a million hectares. This neo-feudalism is only intensifying, as more and more land is annexed for the current boom in sugar cane. Plantations displace forests and pesticides lay waste to waterways. Around 17 litres of noxious stillage is created for every litre of ethanol that rolls off the production line.

And when the economic bust arrives, as it invariably does, you can be sure that it will be those at the bottom of the heap that will come out worst off, warns Thorlby.

Human rights abuses easily slip by unnoticed in a system rife with corruption and bribery. ’Who needs subsidies when you own the judge?’ As of 1998 sugar barons owed tens of millions in fines for crimes against the environment, debts that have not been, or are likely to be, settled. Many deaths have directly resulted from the system, from transport accidents, overwork and even assassinations. Thorlby himself has received numerous death threats for his activism. The Padre considers the current Brazilian model as a classic case study in the unseen costs of western capitalism and points out that ’some crimes’, given enough time and distance, ’become institutionalised’.

Thorlby’s remedy: land reform in Brazil and more responsibility from the developed world. Biofuels are considered by many to be only useful as an energy stop-gap, to be used while our modern society weans itself off fossil fuels, rather than being a long-term solution. Perhaps our time and money would be better spent developing sustainable alternative energy sources from within our own country, instead of importing spurious clean energy from half a world away.

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Resolution from the public meeting: ‘The Reality behind Brazilian biofuels in New Zealand,’ presentation by Padre Thorlby, Pastoral Lands Commission (CPT) Brazil, followed by a panel discussion, held on Earth Day, 22 April 2010, 6 — 8.40pm, at St John’s Hall, Wellington, corner Willis/Dixon Streets.

Resolution: ’This meeting calls for the NZ government to halt the import of biofuels from Brazil and other third world countries because of their unsustainable production and their social and environmental impacts and calls for a mandatory sustainability code for biofuels.’

The Meeting was organised by the Pacific Institute of Resource Management, PIRM, and supported by the Latin American Solidarity Committee; the Alternative Technology and Living Association & Friends of the Earth NZ. – see http://pirm.org.nz/events.html and for recording see – http://www.archive.org/details/TheRealityBehindBrazilianBiofuelsInNewZealandWithPadroTiagoThorlby

The Panel was chaired by economist Bill Rosenberg, NZ Council of Trade Unions, and included Paul Bruce, Wellington Regional Councillor; Father Gerard Burns, chair of Caritas/ social justice worker; Doug Clover, convenor, Sustainable Energy Forum; Jim Kebble, founder, Commonsense Organics and Kay Weir, Editor, Pacific Ecologist – see issue 17 at www.pacificecologist.org and biofuels submissions at www.pirm.org.nz

Tiago Thorlby 2

Photos (c) Matthew Wood 2010

Two Birds, One Stone Matthew Wood Apr 15

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P1110243Each year the School of Biological Sciences and the School of Geography, Environment and Earth Sciences at Victoria University of Wellington join forces to take 2nd year science students to Lake Rotoiti in Nelson Lakes National Park. The Environmental Studies/Biology 222 paper combines the two complementary disciplines in a single field trip.

The course takes a holistic approach to explaining the environment of the area, exploring the intricate interconnections between geology, geomorphology, and the floral and faunal assemblages. At one moment students are shown the control of vegetation by geology — the alkaline soils derived from the ultramafic ophiolite rocks of the Red Hills provide sustenance for only a thin cover of the most undemanding scrub — the next, how forest cover (or the lack of it) can alter natural denudation rates by orders of magnitude. Fire ravaged the forest cover on the north face of Mt. Robert in the early 20th century, leading to ever-deepening scree-filled gullies and the reactivation of dormant colluvial fans.

The landscape of Lake Rotoiti has largely been hewn from the geological basement by glaciers, which have advanced periodically throughout the Quaternary. Today the ice is long gone, but its legacy is written in landforms; a moraine here, a truncated spur or two there. The barren mountain slopes left behind  by retreating ice at the end of the last glaciation have been transformed into stratified soils by untold generations of beech forest. Choruses of tui and bellbirds fill the canopy at lower elevation while weka and New Zealand robins forage for terrestrial invertebrates across the forest floor below.

The major assessment for the course requires the students to propose and execute a field study in the area using the scientific tools they have been equipped with earlier in the week: soil sampling and description, bird call, insect and tree species identification and landform sketching. The second week is coming to an end and the group projects are looking good! Hopefully students from each academic camp will go home appreciating that when it comes to understanding our natural environment, the perspectives of geologists and biologists are by no means mutually exclusive.

Photos (c) Matthew Wood 2010

Pano Rotoiti Crop

“And ice, mast-high, came floating by…” Matthew Wood Mar 29

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Unlike Coleridge’s Ancient Mariner, unwillingly blown there by a tyrannous storm-blast, the modern day seafarers aboard the JOIDES Resolution traveled to the Antarctic coast very much on purpose, following many years of preparatory work to identify the best sites to drill and retrieve sediment cores from beneath the sea floor.

In early January, after wowing the curious youngsters of the GNS Science educational program Discover Ancient Worlds, the Resolution left New Zealand waters and navigated the increasingly sea ice-littered Southern Ocean to reach the polynya coast of Wilkes Land. Cold, dense katabatic winds flowing off the East Antarctic Ice sheet push free sea ice away from this coast and deliver iron-rich terrestrial dusts to the resultant open waters, which fertilise massive algal blooms.

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But getting there is only half the challenge. Once the Resolution arrives at its desired drilling location, there is the problem of itinerant icebergs that care little for the logistical conveniences of scientists. If need be the Resolution can pause drilling operations (that run 24/7 by the way), lift the drill pipe free of the sea floor, graciously make way for the icy behemoth bearing down on the site, and then find and re-enter the hole in the sea floor to continue drilling. Carrying out such engineering gymnastics in 4000 metre-deep water is no small feat.

By observing signals in marine sediments deposited during past warm extremes and times of abrupt climatic warming, the investigators will be better placed to make predictions about what kind of environmental change we can expect in Antarctica in association with anthropogenic global warming.

The classical view of Antarctic ice sheet evolution has been of unstable ice sheets beginning to form around 35 million years ago, with continental ice sheets becoming relatively stable around 13.5 million years ago. However, as Rob McKay of the Antarctic Research Centre points out, this view is based mainly on evidence from deposits at high elevation sites in the Transantarctic Mountains and McMurdo Dry Valleys. The initial results of ANDRILL suggest that there have been significant fluctuations of the marine margin of the generally sub-sea-level-grounded West Antarctic Ice Sheet during the last 14 million years. Extensive parts of the marine margin of the East Antarctic Ice Sheet are also grounded below sea level.

What was happening on the coasts of East Antarctica during this time? How do the climate, ice sheets and ocean currents interact? What does the sedimentary record from coastal Antarctica tell us about conditions in the greenhouse worlds of the past? With the research cruise successfully completed, these questions and more can now begin to be answered by Rob and others in the international science team.

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To download the podcast for your iPod, simply search and subscribe for free through the iTunes Store. For playback on other portable media devices please download from the Journeys to the Ice homepage. Otherwise you can listen straight away by clicking on the link below.

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Photos (c) Rob McKay 2010

A Journey to the Ice Matthew Wood Mar 15

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My last job before heading overseas in mid-2007 (following months of sedimentary grain size analysis on the then recently collected McMurdo Ice Shelf ANDRILL core) was to put together a short film for the Antarctic Research Centre.

As I mentioned in the third episode, the ARC has an annual educational outreach programme aimed at getting local school children enthused about Antarctic science. The project brief was to give an overview of Antarctic field work in a 10-15 minute film aimed at primary to intermediate school-age kids. I decided to structure the narrative around a typical journey to the ice, which, of course, eventually became the film’s title and several years later led to the name of this podcast and blog. In addition to documenting scientific field work on the Victoria Land coastal glaciers and the McMurdo Dry Valleys, the film provides a glimpse of what life at Scott Base is like, and showcases the nearby historic huts and some of the local wildlife.

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The film is cobbled together from footage collected by ARC scientists, Warren Dickinson and Nancy Bertler, and from the 2005/2006 season Project K Youth on Ice expedition. Also making an appearance are the guys from Webster Drilling & Exploration Ltd. who have had a long-standing professional relationship with the ARC. I should say a big thank you to Hayden Saunders for composing the soundtrack, which previous listeners of the podcast may recognise.

The vidcast is optimised for playback on iPhone and iPod Touch, but will play on any video-capable iPod. To download the vidcast for your iPod, simply search and subscribe for free through the iTunes Store. For playback on other portable media devices please download from the Journeys to the Ice homepage. Otherwise you can watch it straight away by clicking on the link below (it may take several minutes to load so please be patient!).

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Photo (c) Matthew Wood 2003

Riders on the Storm Matthew Wood Feb 28

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Turns out there are no reservations about hitchhiking in Antarctica.

On the Victoria Land coast, microscopic particulate matter, from volcanic ash to sea salt, powdered rock to helicopter exhausts, make a habit of snatching free rides on the winds of Ross Sea cyclonic systems or on the gravity-driven katabatic gales that flow off the ice sheets most ferociously during the long dark of the Antarctic winter.

Microscopic View Snow Samples

The Evans Piedmont Glacier is a small ice dome that sits on the coast, snuggled between the McMurdo Dry Valleys and the lofty Transantarctic Mountains to the west, and the Ross Sea to the east. With the McMurdo Volcanic Group to the south and a handful of research stations nearby, it’s the perfect repository for stray aerosols whose chemistries recount a tale of changing local wind patterns. In the summer of 2007, Julia Bull of the Antarctic Research Centre travelled to Evans to read that story for herself.

The study is the first of its kind in the area to analyse the snowpack for a broad suite of major and trace elements. Four to five metre-deep snow pits, burrowed into the glacier surface, reveal a continuous profile of snow accumulation clearly marked out by low-density summer hoar horizons. To descend into such a snow pit is to step back in time well over a decade. The annual snow layers — while outwardly unassuming — are actually a detailed chronicle of climatic change as shown by fluctuations in a range of proxies, including: particulate matter elemental concentrations; stable isotopes of hydrogen and oxygen, which respond to seasonal temperature change; and methanesulphonate, an atmospheric acid that forms in response to primary productivity in the surface layer of the ocean and is indicative of summer accumulation when the Ross Sea is relatively free of sea ice.

Many terrestrial mineral dust element concentrations correlate well with annual maximum wind speed, but with marine aerosol the relationship isn’t as clear. Inter-annual changes are revealed when plotting the ratio between certain terrestrial- and marine-sourced elements, mirroring equivalent shifts in mean summer wind strength at a sub-decadal frequency. Weather station temperature measurements document a similar pattern, which included a cooling of the Victoria Land coast during the 1990s.

Wind Sculpted Snow

Climate change deniers predictably pounce on any climate records that show a cooling trend, but often their ‘interpretations’ will ignore how localised the signal is or fail to consider the effects of natural climate variability superimposed on a human-induced global warming trend. Julia’s findings support the claim that the Ross Sea climate experiences regular forcing by the El Niño-Southern Oscillation, which periodically enhances the inflow of cold continental air masses from the south.

Studies like Julia’s, set within the timescale of instrumental climate records, are extremely important in calibrating the paleo-climate proxy toolbox that can then be applied to the longer-term climate histories provided by ice cores.

To download the podcast for your iPod, simply search and subscribe for free through the iTunes Store. For playback on other portable media devices please download from the Journeys to the Ice homepage. Otherwise you can listen straight away by clicking on the link below.

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Figure (c) Julia Bull 2009. Photo (c) Matthew Wood 2003

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