Posts by Souvik Chatterjee

Roundup: Mélange, Ice Microstructures and Ice Caps

Posted by on Apr 17, 2017 in All Posts, Featured Posts, Roundup, Science | 0 comments

Roundup: Mélange, Ice Microstructures and Ice Caps

Spread the News:ShareRoundup: Mélange, Microstructures and Ice Caps Breakup of Mélange Increases Calving From the Journal Nature Communications: “At many marine-terminating glaciers, the breakup of mélange, a floating aggregation of sea ice and icebergs, has been accompanied by an increase in iceberg calving and ice mass loss. Previous studies have argued that mélange may suppress calving by exerting a buttressing force directly on the glacier terminus. In this study, I adapt a discrete element model to explicitly simulate mélange as a cohesive granular material. Simulations show that mélange laden with thick landfast sea ice produces enough resistance to shut down calving at the terminus. When sea ice within mélange thins, the buttressing force on the terminus is reduced and calving is more likely to occur.” Read more about the study here.     Ice Microstructures and Fabrics of Guliya Ice Cap From Journal Crystals: “This work is the first in the general natural ice literature to compare microstructures and fabrics of continent-type mountain ice in mid-low latitudes with polar ice in order to find out how they evolved based on similar fabric patterns of their vertically girdles. Microstructures and fabrics along the Guliya ice core on the Tibetan Plateau, China, were measured at a depth interval of approximately 10 m…  The thermal kinemics caused by the temperature can play a vital role in different stress cases to cast the similar or same fabric patterns. Normal grain growth, polygonization/rotation recrystallization, and migration recrystallization play roles of different importance at different depths.” Read more about the study here.   The Projected Demise of Barnes Ice Cap From American Geophysical Union: “As a remnant of the Laurentide Ice Sheet, Barnes Ice Cap owes its existence and present form in part to the climate of the last glacial period. The ice cap has been sustained in the present interglacial climate by its own topography through the mass balance-elevation feedback. A coupled mass balance and ice-flow model, forced by Coupled Model Intercomparison Project Phase 5 climate model output, projects that the current ice cap will likely disappear in the next 300 years. For greenhouse gas Representative Concentration Pathways of +2.6 to +8.5 Wm−2, the projected ice-cap survival times range from 150 to 530 years. Measured concentrations of cosmogenic radionuclides 10Be, 26Al, and 14C at sites exposed near the ice-cap margin suggest the pending disappearance of Barnes Ice Cap is very unusual in the last million years. The data and models together point to an exceptionally warm 21st century Arctic climate.” Read more about the study here.   Spread the...

Read More

Tribal House in Glacier Bay Park Recognizes Huna Tlingit

Posted by on Apr 13, 2017 in All Posts, Art/Culture, Featured Posts, News | 0 comments

Tribal House in Glacier Bay Park Recognizes Huna Tlingit

Spread the News:ShareA newly constructed tribal house within Glacier Bay National Park in the Southeast Alaskan panhandle begins a fresh chapter in the contentious relationship between the Huna Tlingit, a Native American tribe, and the National Park Service (NPS). For much of the 20th century, the NPS infringed on Huna hunting rights and appropriated the majority of Huna land to create a monument, and later a National Park and Preserve over 5,000 square miles in area.  The recently opened 28,000 square foot tribal house coincides with the NPS’s 100th anniversary and will serve as a gathering center for the Huna, displaying artwork and cedar carvings, while also informing some of Glacier Bay’s 500,000 yearly visitors about the Huna’s rich culture.  The house sits on the Huna’s ancestral homelands in Bartlett Cove, originally known in the endangered Huna language as L’eiwshaa Shakee Aan, which translates to “Town on Top of the Sand Hill.” It will memorialize the lost clan houses which used to dot the coast but were destroyed by the rapidly advancing Grand Pacific Glacier in the 1700s. The glacier cleared the land, including wildlife like salmon found in the streams, and destroyed Huna villages. But beginning in the 1800s, the glacier began to recede, leaving 100 miles of destruction in its wake. By the 1830s, the wildlife returned, along with the Huna, who set up seasonal camps where they fished, hunted and collected gull eggs and berries. The new tribal house will be the first permanent house since the glacier drove the Huna away to their current village, Hoonah, 30 miles south, where over 800 of them dwell. Remnants of tribal dwellings and other evidence of the Huna’s presence can still be found in the park. For example, cairns are memorials or landmarks made of mounds of stones marking the highlands used to retreat from floods associated with environmental change. In addition, archaeologists have discovered old smokehouses, house pits, and culturally modified trees stripped of bark, which may have been used for markers, baskets, pitch or shelter. Around the time the Huna returned to Glacier Bay, Westerners also arrived. Captain George Vancouver, an English Naval Officer, surveyed the area in 1794, and John Muir, often referred to as the “Father of the National Parks,” visited between 1879 and 1899. Muir is sometimes credited with the discovery of Glacier Bay, although he relied on Tlingit guides to get there. The area was proclaimed a national monument in 1925, a UNESCO World Heritage site in 1979, and finally, a national park in 1980. When the monument decree was passed under President Calvin Coolidge, the Huna Tlingit were not consulted, leading to anger among tribal members, and in addition many tribe members did not speak English. The NPS increasingly infringed on the Huna’s hunting rights, first limiting firearms to protect brown bears in the 1930s, and then ten years later outlawing all hunting and trapping except for seals, which the Park Service later banned in 1976.   In 1992, a Huna hunter in the Park was ordered to appear before a federal magistrate in Juneau for shooting a seal that was going to be used in a potlatch, or ceremonial feast, and his gun was confiscated. Around the same time, the Park Service began considering phasing out commercial fishing which prompted peaceful protests on the shores of Bartlett Cove by the Huna. Speeches were given by elders about Huna history and the importance of subsistence. Following the protests, constructive talks began, and in 1997, the idea for a tribal house was accepted by the Park Service. However, limited funding slowed the tribal...

Read More

Iceberg Scars on Seafloor Offer Clues to the Past

Posted by on Mar 28, 2017 in All Posts, Featured Posts, Science | 0 comments

Iceberg Scars on Seafloor Offer Clues to the Past

Spread the News:ShareMany people know the phrase “tip of the iceberg,” which acknowledges that most of the iceberg sits underwater, but few know what the bottom of an iceberg is capable of. Scientists recently found scars in the North Falkland Basin, north of the Falkland Islands, created by icebergs when they plowed into the seafloor. Known as scours, these u-to-v shaped scars can inform researchers about the Earth’s past in terms of climate, geography and ocean currents. Christopher Brown et al. recently published a paper on the topic in the journal Marine Geology, presenting their latest findings. In the paper, the researchers note that the icebergs responsible for the scours in the North Falkland Basin likely calved from glaciers in the Antarctic Peninsula. The size of the icebergs must have been immense in order for them to travel 2,000 kilometers and still leave marks on the seafloor hundreds of meters below. Given the freshness and reworking of the scours in the North Falkland Basin, researchers believe they likely formed during the Last Glacial Maximum (LGM), the time period when glacier and ice sheets dominated the globe and Antarctica was larger than it is today. Christopher Brown et al. later found and analyzed the scours using five high-quality 3-D seismic data sets covering an area of 1550 km². From analyzing the curvature of the scours, researchers can determine what kind of tides and currents were active thousands of years ago. Scours can also inform scientists about southern hemisphere climatology and ocean patterns. In the North Falkland Basin, Christopher Brown et al. found scours at depths ranging from 280 to 460 meters below sea level, while the depth of the basin reaches up to 2,500 meters. The researchers also located scours measuring nearly 10 meters deep, 38 kilometers long, and one kilometer wide. These scours may have meandered due to the rotation of the iceberg’s keel, or underside, when pushing into the seafloor. External forces that may have also caused a direction change can include ocean currents, tidal changes, subglacial calving, subglacial drainage and storms. Analyzing the location, curvature and orientation of scours provides scientists with insight into the Earth’s past. For example, the icebergs in the North Falkland Basin were likely carried by the East Falkland Current, an important northward current along the east side of Argentina that brings fresh, cold water north from Antarctica. This suggests that the current was active in the LGM and sheds light on the ocean-climate interactions in the southern hemisphere’s past. Christopher Brown et al. determined that a collection of icebergs may have even formed an iceberg “graveyard,” suggesting there may have been an ice bridge from Argentina to the Falkland Islands at some point in time. This means that the icebergs would have traveled on the east side of the Falkland Islands in order to get to the basin. In the northern hemisphere, scour marks have been found far away from where they were sourced, in the low-to-mid latitudes along the southern Atlantic United States coast, for example. In the southern hemisphere, few iceberg scours have been found outside of Antarctica, particularly in the mid-latitudes. The recent findings in the North Falkland Basin support the idea that icebergs could travel into warmer waters farther north of 50°S, the approximate location of the Falkland Islands. Rarely have icebergs been recorded north of the Falklands, but a few mega icebergs were spotted between 1979 and 2003. With much of the ocean floor still unexplored, there are likely more scours yet to be discovered that can tell scientists more about the planet’s past. As the scours in the North...

Read More

Photo Friday: Andean Herders Cope with Climate Change

Posted by on Mar 24, 2017 in All Posts, Communities, Featured Posts, Images | 0 comments

Photo Friday: Andean Herders Cope with Climate Change

Spread the News:ShareAllison Caine was recently living in a community of alpaca herders in the Cusco region of Peru conducting extensive fieldwork as part of her PhD program in anthropology at the University of Michigan. These photographs are an element in her research, which focuses on how alpaca herders evaluate environmental changes and adapt their daily and seasonal practices. In many herding communities in this region,  women are often the primary herders. Glaciers form a key element of Caine’s research. Their rapid retreat in recent decades has altered streamflow and affected the wetlands the herders manage, often negatively. Streamside wetlands are a crucial resource for the herds, particularly in the dry season. The dramatic, visible loss of glaciers has a strong cultural impact as well. The following photos have been provided to GlacierHub courtesy of Allison Caine.               Spread the...

Read More

New Research Offers Fresh Insight into the Iceman’s Death

Posted by on Mar 15, 2017 in All Posts, Featured Posts, News, Science | 0 comments

New Research Offers Fresh Insight into the Iceman’s Death

Spread the News:ShareÖtzi, also known as the Iceman, is showing new signs of life – in his gut. Gabriele Andrea Lugli and other researchers from the University of Parma recently published findings on the Iceman in Microbiome Journal. Their research analyzes samples taken from Ötzi’s gut in order to reconstruct and characterize ancient bacteria to provide clues on how bacteria may have affected humans. While some evidence suggests that the Iceman was murdered or died from the lingering effects of an attack, researchers have now uncovered a new possible cause of death: inflammatory bowel disease. Ötzi was originally found in a receding glacier by two tourists in the Italian Alps in 1991. First thought to be someone from more recent times, research has shown that he lived about 5,300 years ago. Since then, he has become the best known frozen mummy in the world, because his remains are remarkably intact and offer a clear view of the distant past. Though Ötzi’s skin looks like brown caramel and his bones can be seen through his skin, he is very well preserved. Last year, PBS released a documentary titled “Iceman Reborn” about artist Gary Staab, who made a replica of the Iceman using 3D printing. One researcher in the film remarked, “He may well be the most studied human being in history.” Another researcher, referring to new discoveries about Ötzi’s genetic code, noted, “We are rewriting the history of humankind.” It was recently discovered that the Iceman has 61 tattoos, up from a previously smaller number. Ötzi’s tattoos are in locations where there is joint and spinal degradation, indicating the tattoos may have been treatment of some kind. In addition, he was found with a gash on his left hand and an arrow wound in his back, suggesting that he was murdered. He was also found with a copper axe, showing researchers that metalworking was earlier than previously thought. From the Archives: CT scans of ancient mummies show high levels of atherosclerosis, a condition associated with modern risk factors like smoking, obesity, and lack of exercise. Researchers think they know why the ancients also suffered from the disease. archaeology.org/news #archaeology #mummy #Otzi #heart (© Samadelli Marco/EURAC) A post shared by Archaeology Magazine (@archaeologymagazine) on Jan 27, 2017 at 9:54am PST While climate conditions can alter bacterial communities, low temperatures such as permafrost are optimal for long-term DNA preservation. Using a technique called next generation sequencing, the researchers investigated the human gut microbiota in the soft tissue of the human mummy. The samples yielded an enormous amount of data– about 71 gigabases from 12 biopsy samples. Ancient bacteria, such as the ones found in Ötzi’s gut, can provide clues on the history of diseases, the evolution of bacteria and bacterial infections in humans, allowing scientists to reconstruct pathogens like the plague (Yersinia pestis), leprosy (Mycobacterium leprae) and stomach infections (Helicobacter pylori). The researchers found that the upper part of the large intestines had ample Pseudomonas species. These bacteria are typically found in the soil. The presence of P. fluorescens in Ötzi’s intestines suggests that his immune system may have been compromised and that he may have been ill with inflammatory bowel disease at the time of his death. Other findings included the fact that even though modern P. veronii have been isolated from water springs, the ancient strain seems to have the ability to colonize the human gut. The bacteria also shares genetic material with Pseudomonas strains in isolated parts of Antarctica, a fact which supports its ancient origin. Evidence suggests that the evolution of the bacteria was helped by the development of its virulence....

Read More