SciBlogs

Archive February 2010

Riders on the Storm Matthew Wood Feb 28

1 Comment

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.

YouTube Preview Image

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

The Beagle Missed a Trick Matthew Wood Feb 15

1 Comment

In the realm of the Earth sciences (within the cramped offices of competitive post-graduate students at least) there has always been a playful antagonism between ‘hard rock’ and ‘soft rock’ geologists. So I was certainly fraternising with the enemy when I recently caught up with a good friend, Jodi Williams, to hear about her travels south during the past summer.

Jodi studied metamorphic petrology at the School of Geography, Environment and Earth Sciences at Victoria University, culminating in a thesis that probed the temperature and pressure histories locked in the geochemistry of the Alpine schist. Following university, work in the Amazon rainforest and travel through East Africa left her hungry for further adventures into the natural world. So when she had the opportunity to head deep into the untamed Southern Ocean, to explore the remote southernmost outposts of the New Zealand biogeographical region, she jumped at the chance.

Heritage Expeditions is a Christchurch-based company that advocates wildlife conservation through responsible travel. The Enderby Trust provides financial aid to young people who have a passion for the natural sciences, allowing them to travel to the sub-Antarctic Islands of New Zealand and Australia with Heritage Expeditions onboard their research vessel Spirit of Enderby.

Macquarie Island Penguins

The early human history of many of the islands is written in the blood of hapless penguins and marine mammals that were brutally harvested and rendered for natural oils. Native flora and fauna also struggled under the pressures placed on them by exotic species, but serious conservation efforts have been hugely successful in restoring the damaged areas to their former glory. The Snares are close to pristine, with more birds nesting on these tiny islands than there are seabirds around the entire British Isles.* The rich biodiversity and geological significance of the New Zealand and Australian sub-Antarctic islands respectively has earned them UNESCO World Heritage status, and Heritage Expeditions appropriately refers to them as the ‘Galapagos of the Southern Ocean’.

Charles Darwin was openly unimpressed with what he saw of mainland New Zealand during his fleeting visit in 1835. Perhaps, if he had been able to venture further south during his long voyage of discovery, he would have found more than enough birds, beasts and other biota to whet his insatiable appetite for natural wonder.

YouTube Preview Image

Photo (c) Jodi Williams 2009

*Information from Heritage Expeditions website.

A New Year’s Resolution Matthew Wood Feb 01

2 Comments

While I was still busy sunning myself on Coromandel beaches during the first few days of 2010, the research vessel JOIDES Resolution was approaching Wellington Harbour after a record-setting drilling leg off the Canterbury coast.

The Resolution’s sole purpose is to carry out the research objectives of the Integrated Ocean Drilling Program (IODP), the world’s largest multinational geoscience initiative. New Zealand became an official member of the IODP in 2009 under the Australia and New Zealand IODP Consortium (ANZIC), allowing our science community to make use of the program’s world-class drilling ships and platforms.

At 1928 m, the IODP record-breaking core drilled off Canterbury effectively represents the upper limit of this ship’s capabilities — an impressive feat, especially considering that the Resolution can theoretically drill and retrieve such cores in water depths of up to 7 km.

The goal of the IODP is to investigate the Earth system throughout the geological past by collecting sedimentary records captured in the world’s ocean basins. Richard Levy, a paleoclimate scientist at GNS Science, suggests that its major success so far has been in producing a 65 million year global climate record of ice volume, sea level, temperature and CO2 levels, going back far beyond the temporal limit of ice cores.

The educational holiday programme, Discover Ancient Worlds Beneath the Ocean Floor, was run by GNS Science in association with Capital E!, taking advantage of having the JOIDES Resolution in port. Dr. Levy and Julian Thomson, who coordinates education outreach at GNS, put together a week-long course with an over-arching theme of paleoclimate earth science. The participants, aged between 12 and 15, were given a full tour of the drilling ship, stepped inside a -37 degree ice core facility in the Hutt Valley, learned about ice sheets and sealevel rise and handled South Island rocks documenting the Cretaceous-Tertiary (K-T) boundary.

Participants sampling their sediment core

After collecting their own core from the seafloor off the end of Petone Wharf (where Richard’s waterproof watch is currently ticking away, being slowly buried by sediment), these kids experienced the visual feast of examining microfossils under the binocular microscope while learning about the power of these organic remains as proxies for environmental change, as tools for relative and absolute dating, and as indicators of evolution through extinction and speciation.

The JOIDES Resolution may now be busy collecting new sedimentary stories off the Wilkes Land coast of Antarctica, but thanks to an exciting holiday programme, and the talented team behind it, none of these promising young geoscientists have missed the boat.

YouTube Preview Image

Photo (c) Julian Thomson 2010

Network-wide options by YD - Freelance Wordpress Developer