Wiles G.C.,College of Wooster |
Lawson D.E.,Cold Regions Research and Engineering Laboratory CRREL |
Lyon E.,Utah State University |
Wiesenberg N.,1276 Scenic Heights Drive |
D'Arrigo R.D.,Lamont Doherty Earth Observatory
Quaternary Research | Year: 2011
Two interstadial tree ring-width chronologies from Geikie Inlet, Glacier Bay Southeast, Alaska were built from 40 logs. One of these chronologies has been calendar dated to AD 224-999 (775 yr) crossdating with a living ring-width chronology from Prince William Sound, Alaska. Trees in this chronology were likely killed through inundation by sediments and meltwater from the advancing Geikie Glacier and its tributaries ca. AD 850. The earlier tree-ring chronology spans 545. yr and is a floating ring-width series tied to radiocarbon ages of about 3000. cal. yr BP. This tree-ring work indicates two intervals of glacial expansion by the Geikie Glacier system toward the main trunk glacier in Glacier Bay between 3400 and 3000. cal. yr BP and again about AD 850. The timing of both expansions is consistent with patterns of ice advance at tidewater glaciers in other parts of Alaska and British Columbia about the same time, and with a relative sea-level history from just outside Glacier Bay in Icy Strait. This emerging tree-ring dated history builds on previous radiocarbon-based glacial histories and is the first study to use tree-ring dating to assign calendar dates to glacial activity for Glacier Bay. © 2011 University of Washington.
Cordier C.,University of Siena |
Folco L.,University of Siena |
Taylor S.,Cold Regions Research and Engineering Laboratory CRREL
Geochimica et Cosmochimica Acta | Year: 2011
We present major and trace element data of five glass cosmic spherules (CS) with differentiated compositions recovered in the South Pole Water Well and the Transantarctic Mountains, Antarctica. The differentiated CS were first identified using Fe/Mg and Fe/Mn ratios and we have now added high Rare Earth Element concentrations (5
Hopkins M.A.,Cold Regions Research and Engineering Laboratory CRREL |
Knuth M.A.,Cold Regions Research and Engineering Laboratory CRREL |
Green A.,University of California at Berkeley
Earth and Space 2012 - Proceedings of the 13th ASCE Aerospace Division Conference and the 5th NASA/ASCE Workshop on Granular Materials in Space Exploration | Year: 2012
Laboratory testing of equipment for lunar or Martian use is difficult due to the inability to accurately replicate the conditions in these environments (e.g. gravity). While it is important to do laboratory testing at times, modeling provides a low cost way to complete many tests in a repeatable soil bed. This work describes the development of a three dimensional discrete element method (DEM) simulation of a scoop (Surveyor Soil Mechanics Surface Sampler replica) in JSC-1a. The JSC-1a simulant is modeled using non-convex polyhedral grains. Both static and percussive digging tests are completed. Results of the DEM digging tests are compared with results of DEM scoop experiments and simulations reported by Lee et al. (2010). © ASCE 2012.
Lever J.H.,Cold Regions Research and Engineering Laboratory CRREL |
Weale J.C.,Cold Regions Research and Engineering Laboratory CRREL
17th International Conference of the International Society for Terrain Vehicle Systems 2011, ISTVS 2011 | Year: 2011
The National Science Foundation has implemented over-snow traverses to resupply its research stations at South Pole, Antarctica, and Summit, Greenland. Traverse fleets consist of rubber-tracked tractors towing groups of sleds over natural snow, with fuel being the primary cargo. We describe here the evolution of lightweight, high-efficiency fuel sleds for Polar traverses. These sleds consist of flexible bladders strapped to sheets of high molecular weight polyethylene (HMW-PE). They cost 1/6th, weigh 1/10th and triple the fuel delivered per tractor compared with steel sleds. An eight-tractor fleet has conducted three 3,400-km roundtrips to South Pole (2008 - 11) with each traverse delivering ∼ 320,000 kg of fuel while emitting <1% the pollutants, consuming 1/2 the fuel and saving ∼ $1.6M compared with aircraft resupply. A two-tractor fleet in Greenland recently delivered ∼ 83,000 kg of fuel in bladder sleds to Summit with similar benefits. Annual performance monitoring of both traverse fleets has revealed that bladder-sled towing resistance is largely governed by sliding friction. The flexible, low ground-pressure (∼ 7 kPa) sleds produce very little snow-compaction resistance. Sliding friction can start high (μ ∼ 0.2) and drop in half as sleds warm up in response to frictional heating. As with conventional skis, frictional heating probably produces a thin water layer that lubricates the sled-snow interface. Consequently, towing resistance depends on the thermal budget of the sled. For example, black fuel bladders increase solar gain and thus decrease sled resistance; data suggest they could double again the fuel delivered per tractor. While sled durability still needs improvement, the outstanding efficiency and low cost of these sleds has transformed fuel delivery to US Polar research stations.