Saturday, September 04, 2010

Sand Budgeting Advises Sea-Level Rise Planning

By Ms. Green Quick Fixes

Cape Cod was formed between 23,000 and 15,000 years ago by the continental glacier. Each year, sands erode and accrete, but overall, the region suffers a net loss of significant proportions that affects both private property and public utilities.

The small coastal region, currently experiencing various phases of $4 billion to $8 billion worth of water and sewer projects, faces sustainability challenges over the long term due in part to serious erosion that is exacerbated by sea-level rise, according to experts.

The intense storms of just the 2009-2010 winter season caused more than $900,000 in erosion damage to municipal structures and homes and resulted in a $700,000 request to the Federal Emergency Management Agency.

But new geomorphological research advises regional planners about how erosion forces could affect Cape Cod in the future as they prepare unprecedented sewer and water projects.

Graham Giese, a senior scientist at the Provincetown Center for Coastal Studies, and Mark Adams from the National Parks Service are studying former U.S. Coast and Geodetic Survey transects -- known as the Marindin Lines -- that date from 1887 and are developing a GIS-based longshore sediment flux model that estimates the volume rate of change of Cape Cod sediments and can map possible land changes.

Since the lines were established, Cape Cod has lost 2.5 feet of sediment per year -- nearly a football field.

"The outline of the outer Cape is changing. It's changing its attitude and orientation," Giese said.

The total volume of Cape Cod and its surface area will decrease, he explained. Over time, accretion will continue in Provincetown, where the vacuum sewer system is currently being expanded. And barrier beaches in Chatham, a mid-Cape community working on a $300 million sewer expansion, are moving steadily westward.

Giese explained that over time, the geography, hydrology, and other factors of today's estuaries will change. "It's a response of the coast to sea level rise," he said.

For more about the center's research, visit CoastalStudies.org [1].

Wednesday, September 01, 2010

Marine animals suggest evidence for a trans-Antarctic seaway

A tiny marine filter-feeder, that anchors itself to the sea bed, offers new clues to scientists studying the stability of the West Antarctic Ice Sheet – a region that is thought to be vulnerable to collapse.

As part of a study for the Census of Antarctic Marine Life (CAML), scientists from British Antarctic Survey (BAS) analysed sea-bed colonies of bryozoans from coastal and deep sea regions around the continent and from further afield. They found striking similarities in particular species of bryozoans living on the continental shelves of two seas - the Ross and Weddell - that are around 1,500 miles apart and separated by the West Antarctic Ice Sheet.

This new finding, published this month in the journal Global Change Biology, leads the science team to conclude that these animals could have spread across both seas only by means of a trans-Antarctic seaway through what is now a 2 km solid layer of ice. They suggest also that this seaway opened up during a recent interglacial (warm period between ice ages) perhaps as recently as 125,000 years ago when sea level was about 5 metres higher than today.

While some geological evidence suggests that the West Antarctic Ice Sheet (WAIS) collapsed at least once in the last million years, scientists are keen to determine the frequency of collapse and to understand the processes and connections between warm periods and deglaciation events. Elsewhere around Antarctica the marine animals that could help scientists estimate the date when West Antarctica was ice free, were obliterated during ice ages by advancing glaciers that bulldozed their fossil remains off the continental shelf.

This new biological evidence contributes to glaciological investigations focused on the future stability of the WAIS, which may have a major impact on the rate of sea level rise in the coming centuries. Scientists estimate that a complete collapse of the WAIS would raise global sea level by around 3.3 m to 5 m.

Lead author of the paper Dr David Barnes of British Antarctic Survey said,

"The West Antarctic Ice Sheet can be considered the Achilles heel of Antarctica and because any collapse will have implications for future sea level rise it's important that scientists get a better understanding of big deglaciation events. This biological evidence is one of the novel ways that we look for clues that help us reconstruct Antarctica's ice sheet history.

"Our new research provides compelling evidence that a seaway stretching across West Antarctica could have opened up only if the ice sheet had collapsed in the past.

"When we found groups of strikingly similar bryozoans hundreds of miles apart we knew we were onto something very interesting. Perhaps these species had survived the last ice age whereas in all other regions of Antarctica they were wiped out. We know that after the last ice age groups of bryozoans dispersed freely between many of the regions we studied. But because the larvae of these animals sink and this stage of their life is short – and the adult form anchors itself to the seabed – it's very unlikely that they would have dispersed the long distances carried by ocean currents. For the bryozoans on both the Weddell and Ross sea continental shelves to be more similar to one another than to any of those found in the waters in between is striking indeed. Our conclusion is that the colonisation of both these regions is a signal that both seas were connected by a trans-Antarctic seaway in the recent past."

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Issued by the BAS Press Office:

Heather Martin, Tel: +44 (0)1223 221414; mobile: 07740 822229; email: hert@bas.ac.uk

Linda Capper, Tel: +44 (0)1223 221448; mobile: 07714 233744; email: lmca@bas.ac.uk

Scientist contact details:

Dr David Barnes, Tel: +44 (0)1223 221613; Mobile: 07736 921 693; email: dkab@bas.ac.uk

Stunning broadcast-quality footage and stills of Antarctica, along with a copy of the full Global Change Biology paper are available at: ftp://ftp.nerc-bas.ac.uk/pub/photo/DavidBarnes/

Images used should be credited to British Antarctic Survey

Global Change Biology paper: Faunal evidence for a late quaternary trans-Antarctic seaway by David K A Barnes and Claus-Dieter Hillenbrand - see early view online version at: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2486.2010.02198.x/full