One of the largest icebergs ever recorded has just broken away from the Larsen C Ice Shelf in Antarctica. Over the past few years Iâve led a team that has been studying this ice shelf and monitoring change. We spent many weeks camped on the ice investigating melt ponds and their impact â and struggling to avoid sunburn thanks to the thin ozone layer. Our main approach, however, is to use satellites to keep an eye on things.
Weâve been surprised by the level of interest in what may simply be a rare but natural occurrence. Because, despite the media and public fascination, the Larsen C rift and iceberg âcalvingâ is not a warning of imminent sea level rise, and any link to climate change is far from straightforward. This event is, however, a spectacular episode in the recent history of Antarcticaâs ice shelves, involving forces beyond the human scale, in a place where few of us have been, and one which will fundamentally change the geography of this region.
Ice shelves are found where glaciers meet the ocean and the climate is cold enough to sustain the ice as it goes afloat. Located mostly around Antarctica, these floating platforms of ice a few hundred meters thick form natural barriers which slow the flow of glaciers into the ocean and thereby regulate sea level rise. In a warming world, ice shelves are of particular scientific interest because they are susceptible both to atmospheric warming from above and ocean warming from below....
After more than 16 years of operation, NASA's Earth Observing-1 (EO-1) spacecraft was decommissioned on March 30. The EO-1 satellite was a component of NASA's New Millennium Program to validate new technologies that could reduce costs and improve capabilities for future space missions. Aboard EO-1 was the Advanced Land Imager (ALI) instrument developed by MIT Lincoln Laboratory as an alternative to the land-imaging sensor that was used by the Landsat Earth-observing program.
"From its inception, ALI was intended to demonstrate new technologies that would carry on Landsat's more than 30-year legacy of continuous land monitoring while providing substantial size, weight, power, and cost reductions," says Jeffrey Mendenhall, current leader of Lincoln Laboratory's Advanced Imager Technology Group and a member of the ALI development team. "Thirty international Earth science teams evaluated a variety of ALI data â for example, data for agriculture, forestry, urban development, climate, volcanology, glaciology, geology, water management â collected over the first year of operation to assess the instrument's performance relative to Landsat program expectations. The ultimate conclusion was that ALI met, or in many instances, exceeded the Landsat 7 instrument's performance."...
âI had a science teacher who did a short unit on glaciers ⦠I couldnât believe they were real,â she says. That classroom encounter when she was in eight grade in Winchester, Massachusetts, had a lasting impact.
Criscitiello went on to earn MITâs first PhD in glaciology, and now she is an adjunct assistant professor of glaciology at the University of Calgary in Canada. She studies the history of sea ice and polar marine environments, primarily by drilling ice cores on land-based ice sheets and ice caps in both the Arctic and Antarctic. In March, Criscitiello became the technical director of the newly-created Canadian Ice Core Archive at the University of Alberta, where scientists will have access to 1.7 kilometers of core samples.
âThe very northernmost reaches of the Canadian High Arctic are incredibly understudied and underÂsampled,â says Criscitiello. To reach remote sites, she often must take several small prop plane flights and then ski in to the destination. On trips to such places as West Antarctica and Greenland, she has had to camp on ice sheets; in Greenland, sheâs even slept with a shotgun in case of polar bear attacks....
About 10 percent of the Earthâs land mass is covered in glaciers, most of which slip slowly across the land over years, carving fjords and trailing rivers in their wake. But about 1 percent of glaciers can suddenly surge, spilling over the land at 10 to 100 times their normal speed.
When this happens, a glacial surge can set off avalanches, flood rivers and lakes, and overwhelm downstream settlements. What triggers the surges themselves has been a longstanding question in the field of glaciology.
Now scientists at MIT and Dartmouth College have developed a model that pins down the conditions that would trigger a glacier to surge. Through their model, the researchers find that glacial surge is driven by the conditions of the underlying sediment, and specifically by the tiny grains of sediment that lie beneath a towering glacier.
âThereâs a huge separation of scales: Glaciers are these massive things, and it turns out that their flow, this incredible amount of momentum, is somehow driven by grains of millimeter-scale sediment,â says Brent Minchew, the Cecil and Ida Green Assistant Professor in MITâs Department of Earth, Atmospheric and Planetary Sciences. âThatâs a hard thing to get your head around. And itâs exciting to open up this whole new line of inquiry that nobody had really considered before.â...
