glaciology - How was the Marinoan Glaciation triggered?

The Marinoan Glaciation (a.k.a. Elatina Glaciation) was a glaciation that is thought to have occurred towards the end of the aptly-named Cryogenian period at ca. 650Ma. It is particularly known as one of the glaciations that may or may not have been a Snowball Earth. Whether or not this glaciation was truly global, there is evidence that this glaciation existed. But what are the current hypotheses on how this glaciation was triggered?...Read more

glaciology - Is this 70km crack in an ice shelf of Antarctica remarkable, or a regular occurrence?

I've just seen the LiveScience article 70-Mile-Long Crack Opens Up in Anatarctica. I'm not sure if the title is a bit sensational or not, the crack is in an ice shelf, not the continent of Antarctica. An ominous crack in an Antarctic ice shelf as wide as a football field is long takes on an otherworldly beauty in a new aerial image. Snapped by scientists on NASA's IceBridge mission, the shot shows a rift in Larsen C, an ice shelf that is floating off the Antarctic Peninsula. When the crack eventually spreads across the entire ice shelf, it ...Read more

glaciology - Considering how old the Antarctic ice cover is, why isn't it much thicker?

The Wikipedia article on the subject of the "Antarctic ice sheet" says that: The icing of Antarctica began in the middle Eocene about 45.5 million years ago and escalated during the Eocene–Oligocene extinction event about 34 million years ago.The article later says that: Ice enters the sheet through precipitation as snow. This snow is then compacted to form glacier ice which moves under gravity towards the coast.However it looks like, from the photos of Antarctica, that this transfer of ice to the coasts is not happening everywhere on Ant...Read more

glaciology - The giant 6,000 km$^2$ iceberg A-68; will ground-truth telemetry supplement satellite tracking data?

update 2: FIRST images of A-68 iceberg not taken from a satellite in space but from the air are out. On this NASA Earth Observatory web page are areal images from NASA's Operation IceBridge taken from a P-3 aircraft. Will the placement of a GPS tracker/weather monitor or two, or even a seismometer be next?above: The edge of A-68, the iceberg the calved from the Larsen C ice shelf. Photo by NASA/Nathan Kurtz.update 1 : According to the BBC Article British mission to giant A-68 berg approved: The British Antarctic Survey has won funding to visit...Read more

glaciology - Is there a name for this type of ice crystal?

Recently, I took the following picture:I have read about this phenomenon and I think it is caused by water vapour that is pressed out of the ground and then freezes due to low temperature. However, I cannot recall the name of this phenomenon and I couldn't find it on the internet.The picture was taken in the Alps around 3000 meters above sea level in August. I'm pretty sure that the white thing is ice. They're a couple of centimetres long and quite porous. I found them on top of an earthy and slaty flank of a mountain early in the morning (arou...Read more

glaciology - Is "Chasm One" the really the name of this feature on the Brunt Ice Shelf?

The BBC News article Antarctic: No role for climate in Halley iceberg splitting says: With no-one on the ice surface, notice of any breakaway will have to come from automated in-situ instrumentation and from spacecraft observations.The image below shows the current location of Halley Research Station relative to "Chasm One". I like that name. It reminds me of SpaceShipOne and Public Enemy No. 1.Is "Chasm One" an "official" name for the feature? How was the term coined? Will there be a new Chasm One someday, or will the name be retired after th...Read more

glaciology - Why antarctic research stations are built above ground instead of on the ground or underground?

Many online sources stresses how much the antarctic wind is dangerous for the structures and for the personnel, yet most buildings I see are built off the ground.I suppose that is due to the different thermal conductivity of the air vs the ground.Yet, many arctic dwelling tribes build enclosed hut on contact with the ground, as if the wind chill is actually much more dangerous than the heat lost with the ground.Besides, building underground should guarantee an average temperature and/or depending on depth a better temperature for materials and ...Read more

glaciology - Why does glacier ice look blue?

The color of the ice observed in glaciers, icebergs and crevasses is often blue. However, ice cubes and industrial ice blocks are perfectly transparent or white if not.So. Why does glacier ice look blue?Some examples of what I mean:Ice blocksGlacier icePS: As a glaciologist, this is a question I've received a lot, and after Googling for it, the answers I found are not fully satisfactory, so I decided to share mine here in a Q&A format....Read more

glaciology - Giant Cavern the Size of Manhattan Under Thwaites Glacier in West Antarctica

Avery Thompson writes in Popular Mechanics In Thwaites’ case, that radar uncovered a gigantic cavern between the glacier itself and the bedrock below it. That cavern is likely filled with air much warmer than the surrounding ice, triggering faster melting of the glacier than would happen otherwise.From the cited NASA release I would have assumed that the cavity is full of water (if only because ice is not strong enough to support such a large air-filled cavern).Is it air or water?...Read more

glaciology - Giant Cavern the Size of Manhattan Under Thwaites Glacier in West Antarctica - how was satellite and airborne radar data combined?

This is a follow-up question to Giant Cavern the Size of Manhattan Under Thwaites Glacier in West Antarctica.The work is reported in an open access paper in Science: Heterogeneous retreat and ice melt of Thwaites Glacier, West Antarctica which is very technical, thorough, and hard for me to understand.The work is based on a substantial amount of radar data, both SAR (Synthetic Aperture Radar) from several satellites, and (from Pasadena Now) ...by ice-penetrating radar in NASA’s Operation IceBridge, an airborne campaign that began in 2010 and st...Read more

glaciology - Is 2,000 years from now a credible figure for return to glaciation?

I read this article, https://www.technologyreview.com/s/416786/global-warming-vs-the-next-ice-age/"In about 300 years, all available fossil fuels may well have been consumed.Over the following centuries, excess carbon dioxide will naturally dissolve into the oceans or get trapped by the formation of carbonate minerals. Such processes won’t be offset by the industrial emissions we see today, and atmospheric carbon dioxide will slowly decline toward preindustrial levels. In about 2,000 years, when the types of planetary motions that can induce po...Read more

glaciology - How are the thickness of ice sheets from previous glaciation periods determined?

How is the thickness/depth of ice sheets from previous glaciation periods determined? I've for instance often seen statements that the ice sheet over Scandinavia at the last glacial period maximum (i.e. Weichel) was 3-4 km thick, but haven't seen how this is calculated. Is this determined only by the rate of subsequent post-glacial rebound, basically the inferred weight of the ice sheet, or is it based on other information as well (e.g. historical sea levels as an estimate of the amount of water tied up in ice sheets)?...Read more