Ice Stories: Dispatches From Polar Scientists » audio dispatch http://icestories.exploratorium.edu/dispatches Mon, 15 Nov 2010 20:40:36 +0000 http://wordpress.org/?v=2.9.2 en hourly 1 The Sound of Ice http://icestories.exploratorium.edu/dispatches/the-sound-of-ice/ http://icestories.exploratorium.edu/dispatches/the-sound-of-ice/#comments Fri, 20 Mar 2009 19:52:50 +0000 Exploratorium Crew http://icestories.exploratorium.edu/dispatches/?p=1578 SAN FRANCISCO, CALIFORNIA– (By Dia Felix and Wayne Grim) Terje Isungset is one of Europe’s most accomplished and innovative percussionists. With over two decades experience in jazz and Scandinavian music his work travels far beyond traditional boundaries. He’s become more like a cross between a sound artist and a shaman. Isungset crafts his own instruments from natural elements found in Norway such as arctic birch, granite, slate and even ice. We interviewed Terje as part of the Exploratorium Audio Salon series. Click below to listen.


Precision-carved ice wind chimes, drum, and rattlers. Photo courtesy of Terje Isungset.
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Why We Install GPS Systems http://icestories.exploratorium.edu/dispatches/why-we-install-gps-systems/ http://icestories.exploratorium.edu/dispatches/why-we-install-gps-systems/#comments Mon, 08 Dec 2008 02:32:34 +0000 Kelly Carroll http://icestories.exploratorium.edu/dispatches/?p=1265 DEVERALL ISLAND, ANTARCTICA– The POLENET project installed their newest high-precision GPS system on Deverall Island, Antarctica. These GPS systems tell us how much the ground underneath the ice sheet is moving upward. This has important implications on the movement of the West Antarctic Ice Sheet and its interplay with the rock below.

Click below to hear more about it.


Deverall Island, the southernmost island in the world. It is located at the western margin of the Transantarctic Mountains on the Ross Sea Ice Shelf.

The frame that holds all the electronics, weather stations, satellite modems to transfer data, and the solar panels and batteries used for powering the system continuously throughout the year.

The ski-equipped de Havilland Twin Otter aircraft that is used to transport science teams to field sites in Antarctica.
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Life on the West Antarctic Ice Sheet http://icestories.exploratorium.edu/dispatches/life-on-the-west-antarctic-ice-sheet/ http://icestories.exploratorium.edu/dispatches/life-on-the-west-antarctic-ice-sheet/#comments Wed, 26 Nov 2008 06:30:51 +0000 Jake Walter http://icestories.exploratorium.edu/dispatches/?p=1204 WHILLANS ICE STREAM, ANTARCTICA– In this audio dispatch, I describe our first week in our field camp on the West Antarctic Ice Sheet. Hear about our research on lakes under the glaciers and get a slice of life as a remote polar scientist.


The Under the Glaciers project field camp on the West Antarctic Ice Sheet during the 2007 season.
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Escorting Dynamite Through Siple Dome http://icestories.exploratorium.edu/dispatches/escorting-dynamite-through-siple-dome/ http://icestories.exploratorium.edu/dispatches/escorting-dynamite-through-siple-dome/#comments Tue, 25 Nov 2008 19:50:24 +0000 Saffia Hossainzadeh http://icestories.exploratorium.edu/dispatches/?p=1192 WHILLANS ICE STREAM / ICE STREAM B, ANTARCTICA– In these two audio dispatches, I describe our journey to our field site via a stop at Siple Dome station. In part one, hear about the difficulties involved in escorting 700 pounds of explosives through Antarctica. In part two, hear about our combat-style landing at Siple Dome’s remote air strip.

Part I

Part II


The main structure at Siple Dome.
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Journey http://icestories.exploratorium.edu/dispatches/journey/ http://icestories.exploratorium.edu/dispatches/journey/#comments Fri, 24 Oct 2008 21:30:03 +0000 Andrea Balbas http://icestories.exploratorium.edu/dispatches/?p=827 MCMURDO STATION, ANTARCTICA– If you think all scientists are confined to the sterile environment of a lab, you’d be ill-informed. Science can take you around the world, to see places and things unimaginable.


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Ears of the Deep: Hydrophone Arrays http://icestories.exploratorium.edu/dispatches/ears-of-the-deep-hydrophone-arrays/ http://icestories.exploratorium.edu/dispatches/ears-of-the-deep-hydrophone-arrays/#comments Wed, 27 Aug 2008 20:05:17 +0000 Kevin Fall http://icestories.exploratorium.edu/dispatches/?p=664 ABOARD THE USCGC HEALY, ON THE BEAUFORT SEA– While much of the Coast Guard personnel continued to host the distinguished visitors, the science work increased in tempo. The primary science activity to be accomplished on the cruise is to recover and deploy moorings.

Moorings can be used for a variety of purposes, but for this cruise moorings are being used to keep acoustic and oceanographic sensors in place for some period of time (typically a year). Scientist Kate Stafford from the University of Washington’s Applied Physics Lab (APL) has a set of acoustic sensors forming a ‘hydrophone array’ that are to be recovered and (re) deployed later in the cruise.

Hydrophones are passive measuring devices– they do not emit any sound themselves, but instead convert acoustical energy in the water to an electrical signal. Kate analyzes the sounds or “vocalizations” of whales, bowhead and beluga whales in particular, using these instruments. Fixing a hydrophone array in place underwater for a relatively long period of time (a year) allows scientists to listen for the presence of cetaceans (whales, dolphins, and porpoises) from multiple locations, even in poor weather conditions.


Kate pictured with a large mooring float.

Detection Using Passive Hydrophone Arrays

Each hydrophone Kate uses sits inside an instrument that includes the hydrophone itself, a data recorder where the digitized audio samples are stored for later retrieval, and a pack of batteries to keep the whole instrument running for a year or more. These are the instruments that are attached to moorings that are deployed out at sea until they are recovered. When these types of instruments are placed sufficiently close together, more than one will pick up the same vocalizations or sound. When this happens it may be possible to locate and track a particular sound source (animal or otherwise) over time. When the instruments are used together in this way, they behave as an array, or group that is acting together cooperatively. Hydrophone arrays can also be used in estimating animal populations, although gaining high confidence using this approach is an ongoing challenge.


The hydrophone instrument.

When the data from Kate’s instruments is recovered, it can be processed in a number of ways. One way is to simply listen to the sounds on the recordings. A person with enough expertise in doing this can pick out some of the vocalizations and other sounds. As an example, you can listen to the recording of a beluga:

Beluga Whale Recording

A more quantitative approach involves taking the data and analyzing the frequency, timing and intensity (loudness) of particular sounds. A popular way of doing this is to visualize this information on a special kind of graph called a spectrogram. In this spectrogram of a beluga vocalization in the Beaufort sea, for example, the intensity of sound at a particular frequency at a particular time is indicated by the color (blue less intense; red most intense).


Spectrogram of beluga soundings in the Beaufort Sea.

By looking at the spectrogram or other types of graphs (or by using a computer program to do so), acoustic frequency patterns resulting from cetacean vocalizations (or boats, or the sounds of airguns used in seismic exploration, etc.) can be found.

For the interested reader, the analysis of hydrophone data is similar to both signal processing and image processing techniques. Common techniques include matched filters, band-limited energy summation and classification, image matching techniques on the spectrogram or time series, and other frequency-domain analysis techniques such as wavelet-based decomposition. A more detailed explanation of how this can be accomplished and why fixed passive arrays are useful for monitoring cetaceans is given in this paper.

The ultimate goal for much of the related science here is to estimate animal populations, which is important for both ecological understanding and policy-setting reasons. As suggested above, there are a number of factors posing challenges to doing this effectively using acoustic arrays. Animals may use different vocalizations at different points in time and these may vary in many ways (e.g., frequency, phase, amplitude, modulation, etc) based on its activity (e.g., feeding or seeking a mate). In addition, instruments are only capable of detecting a signal up to some distance (which depends on frequency), so forms of statistical inference must be employed in an attempt to estimate a population given a number of detections.

Necessarily, these are only estimates, but they are estimates based on measured data, and moored acoustic arrays offer some significant advantages for making such measurements versus the alternatives of visual observation from ships (or other platforms like airplanes, etc) or from towed hydrophones that only last a few days or weeks. Moorings last a long time and are relatively immune to poor weather so they can offer a richer data set on which to base estimates. Of course, they need to be designed, deployed, and recovered, which generally involves a ship such as HEALY

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Northern Exposure http://icestories.exploratorium.edu/dispatches/northern-exposure/ http://icestories.exploratorium.edu/dispatches/northern-exposure/#comments Tue, 27 May 2008 21:35:41 +0000 Exploratorium Crew http://icestories.exploratorium.edu/dispatches/?p=193 BARROW, ALASKA– (By Ronald Aveling) In this slideshow dispatch we open up the aperture on our trip to Barrow, Alaska.

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Finishing Our Field Work http://icestories.exploratorium.edu/dispatches/finishing-our-field-work/ http://icestories.exploratorium.edu/dispatches/finishing-our-field-work/#comments Tue, 18 Dec 2007 16:16:16 +0000 Nadine Quintana Krupinski http://icestories.exploratorium.edu/dispatches-new/?p=109 In this latest audio dispatch, I describe the end of our field work here–taking down our camp and setting our devices so they continue to collect data for us for the next two years.

nasa_wais_ice_streams.jpg
In this image of Antarctica, you can see the location of Whillans Ice Stream, where we’ve been living for the past three weeks.
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The Barrier to Lake Conway http://icestories.exploratorium.edu/dispatches/the-barrier-to-lake-conway/ http://icestories.exploratorium.edu/dispatches/the-barrier-to-lake-conway/#comments Sun, 16 Dec 2007 16:16:56 +0000 Nadine Quintana Krupinski http://icestories.exploratorium.edu/dispatches-new/?p=111 In this audio dispatch I describe our team’s attempt to travel to Lake Conway, one of the sites where we were planning to place our GPS instruments. On the way there, however, our team found a crevasse blocking the route.

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The Skidoo Situation http://icestories.exploratorium.edu/dispatches/the-skidoo-situation/ http://icestories.exploratorium.edu/dispatches/the-skidoo-situation/#comments Wed, 12 Dec 2007 16:17:40 +0000 Slawek Tulaczyk http://icestories.exploratorium.edu/dispatches-new/?p=114 In this audio dispatch I describe our skidoo mishaps, and how our bad luck was swiftly followed by aid and good fortune.

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