Home / Tag Archives: ice

Tag Archives: ice

Greenland Ice, Changing Albedo, and a Feedback Loop

The BBC reports: Sea Level Fears as Greenland Darkens. The article discusses a possible feedback loop where as temperatures warm algae growth may flourish, which darkens the surface and changes the albedo to increase melting.

One concern now is that rising temperatures will allow algae to flourish not only on the slopes of the narrow margins of the ice-sheet but also on the flat areas in the far larger interior where melting could happen on a much bigger scale.

We joined the latest phase of research in which scientists set up camp on the ice-sheet to gather accurate measurements of the “albedo” or the amount of solar radiation reflected by the surface.

White snow reflects up to 90% of solar radiation while dark patches of algae will only reflect about 35% or even as little as 1% in the blackest spots.

Other highlights from the article include:

Currently the Greenland ice sheet is adding up to 1mm a year to the rise in the global average level of the oceans.

It is the largest mass of ice in the northern hemisphere covering an area about seven times the size of the United Kingdom and reaching up to 3km (2 miles) in thickness.

This means that the average sea level would rise around the world by about seven metres, more than 20ft, if it all melted.

You can get Greenland Ice Data from NASA’s Vital Signs of the Planet page as noted in a past post.

A Trillion Ton Iceberg

Map of Larsen C, overlaid with NASA MODIS thermal image from July 12 2017, showing the iceberg has calved

If you have been following this blog you might know that we are talking about Larsen C. Project MIDAS reports: Larsen C calves trillion ton iceberg. What does this mean?

The iceberg weighs more than a trillion tonnes (1,000,000,000,000 metric tonnes), but it was already floating before it calved away so has no immediate impact on sea level. The calving of this iceberg leaves the Larsen C Ice Shelf reduced in area by more than 12%, and the landscape of the Antarctic Peninsula changed forever.

The article also notes:

Whilst this new iceberg will not immediately raise sea levels, if the shelf loses much more of its area, it could result in glaciers that flow off the land behind speeding up their passage towards the ocean. This non-floating ice would have an eventual impact on sea levels, but only at a very modest rate.

There is now some interesting modeling of where the iceberg will go and how long it will take to melt.  There should be a good differential equations project in here. Please read the full article, which includes a nice picture of the full break in the ice. Quiz question: What melting ice will have a significant impact on sea level?

Arctic Ice and Global Warming

An article from this past February, Rapid warming and disintegrating polar ice set the stage for ‘societal collapse’ – Carbon pollution is destabilizing both the Arctic and Antarctic, provides a nice overview of issues of warming and ice. For instance, there is the albedo feedback loop:

Climate models have long predicted that if we keep using the atmosphere as an open sewer for carbon pollution, the ice cap would eventually enter into a death spiral because of Arctic amplification — a vicious cycle where higher temperatures melt reflective white ice and snow, which is replaced by the dark land or blue sea, which both absorb more solar energy, leading to more melting.

The graph here is historical January Arctic ice extent and the data can be downloaded from the National Snow and Ice Data Center Sea Ice Data and Analysis Tools page.  Go to Sea ice analysis data spreadsheets and then to monthly data by year. As you’ll see there is other data there worth exploring. There are projects using Arctic ice data on both the calculus and statistics pages on this blog. If you are a real ice junkie take a look at the interactive sea ice graph and keep track of the current ice extent.  Finally, as a reader of this blog you know that you can make your own global temperature maps like the one in the article from reading April Second Warmest on Record.

 

 

Glacier Pairs

NASA’s Global Ice Viewer for Glaciers provides stunning pairs of images of glaciers taken many years apart at the same location. The viewer starts with a map of the world with links for seven locations. Each link brings you to glacier pair images from that location with information about the images. For example, here is a pair of images from Bear Glacier in the Alaskan Range. The top image was taken on July 20, 1909 and the second on Aug 5, 2005. Here is what the site says about glaciers:

Glaciers are sentinels of climate change. Ice that took centuries to develop can vanish in just a few years. A glacier doesn’t melt slowly and steadily like an ice cube on a table. Once glacial ice begins to break down, the interaction of meltwater with the glacier’s structure can cause increasingly fast melting and retreat.

Widespread loss of glaciers would likely alter climate patterns in complex ways. Glaciers have white surfaces that reflect the sun’s rays.  This helps keep our current climate mild. When glaciers melt, darker surfaces are exposed, which absorb heat.  This raises temperatures even more.

Larsen C Update

Project MIDAS recently posted Larsen C takes another step towards calving.

In the largest jump since January, the rift in the Larsen C Ice Shelf has grown an additional 17 km (11 miles) between May 25 and May 31 2017. This has moved the rift tip to within 13 km (8 miles) of breaking all the way through to the ice front, producing one of the largest ever recorded icebergs. The rift tip appears also to have turned significantly towards the ice front, indicating that the time of calving is probably very close.

STEM folks are presented with challenging problems modeling and predicting changes in ice and glaciers due to climate change.

Arctic Sea Ice Visual

Thanks to the folks at the NASA Scientific Visualization Studio for this visualization of Annual Arctic Sea Ice Minimum 1979-2015 with Area Graph (click on the visual to play). Arctic ice data is available in the calculus and statistics sections. A recent Economist article The thawing Arctic threatens an environmental catastrophe adds some context.

The Arctic has been warming at twice the rate of the rest of the world for decades because of feedback loops that have reduced the albedo effect, a measure of the way Earth reflects heat. Unlike the rest of the planet the polar regions release more heat into space than they absorb, in effect cooling the planet, because sunlight is reflected by ice and snow. When it is replaced by water or dark ground, more heat is retained. That is precisely what is happening in the Arctic’s defrosting landscape.

Larsen C in the News

The crack in the Larsen C ice shelf has been in the news recently. For instance Newsweek’s Another Huge Crack has Appeared on the Antarctica’s Larsen C Ice Shelf or the BBC’s The Crack that is Redrawing the World’s Map. Both articles seem to stem from the Project Midas news release A new branch of the rift on Larsen C (they made the map here).  The Newsweek article notes:

Current projections indicate that if the Larsen C ice shelf disintegrates, it could raise sea levels by up to 10cm.

A NASA report, Breaking the ice: Antarctic rifts and future sea level is a little more precise:

Yet even if the whole ice shelf were to break up, Fricker said, the resulting sea level rise would be minimal. The glaciers held back by the shelf are not so imposing.

“The Larsen C ice shelf only holds back about one centimeter of global sea level rise,” she said.

Still, the crack in Larsen C could be a bellwether for ice shelves elsewhere on the continent, Rignot said.

“What we are seeing on Larsen C has implications for the big ice shelves farther south that hold considerable (sea level) potential,” he said. The loss of these larger ice shelves and the resulting acceleration of glacial calving could amount to meters of sea level rise in the decades and centuries to come.

The NASA article does provide some balance:

Ice shelf demise, or business as usual?

The crack could be the start of a period of sustained retreat, similar to what happened to Larsen B, said Ala Khazendar, a JPL scientist who has investigated both Larsen B and Larsen C. An increasingly weakened ice shelf allows glaciers to speed their flow into the ocean, and the shelf, unable to recover its former bulk and solidity, disintegrates.

Or, this could turn out to be a normal calving episode.

“We have no way yet of knowing whether Larsen C is doing what Larsen C has been doing for thousands of years, or whether we are witnessing the beginning of the end of Larsen C,” he said.

If you are talking about climate change in the classroom, the NASA article is excellent for further readings and discussion as well as the Project Midas site. There is some interesting science here in understanding ice.

Greenland Ice Mass and Data

Vital Signs of the Planet from NASA is a place for graphs and data. The graph here is change in the mass of the Greenland Ice Sheet. On the Land Ice page there is also a graph of changes in the Antarctica Ice. Underneath each graph is a link to data (HTTP), which will give you data for both Greenland and Antarctica ice as well as sea level change. All three sets can be used for linear regression or multiple regression predicting sea level change based on both ice mass changes (recall that melting sea ice doesn’t raise sea levels but land ice does).