Discussion

More About Glaciers

Greenland

Last week, we talked about Antarctica's ice sheet. Here is some information about Greenland.

Greenland's ice sheet covers about 80% of the island's surface. Its volume of ice is about 0.7 million cubic miles, covering an area of 656,000 square miles, three times the area of Texas. Global warming and iceberg calving is causing Greenland to lose ice at the average rate of about 270 billion tons of ice annually. From 1992 to 2020, Greenland's ice loss contributed about ¾ of an inch to sea level rise. The rate of ice loss is accelerating. 

The Petermann Glacier is among the largest portions of Greenland's continental ice sheet with direct contact with the sea. 

Petermann is generally retreating, and its flow is accelerating. In 2010, a 97-square mile iceberg broke off the front. Two years later, another massive iceberg, 12 square miles in area, broke off. The glacier is thinning from water melting underneath. Nearly all of Greenland's glaciers are losing mass at a high rate.

The image below show what Greenland would like if all of its ice melted.

If greenhouse gasses continue to rise at the current rate, it is estimated that Greenland's ice will be all gone in about 10,000 years. If that were to occur, sea levels would rise over 23 feet. Right now, Greenland's ice sheet is near a tipping point where melting may become irreversible. Some think that tipping point may be reached this year. It is expected that melting from Greenland alone will cause a sea level rise of 10 inches by 2100. Antarctica and Greenland combined are expected to account for a 3-to 6-meter sea level rise by 2100.

Miami is currently experiencing flooding from high tides a few times a year.

It is projected that that will occur 45 to 85 times a year by 2050 depending on the location. The city and state is spending billions of dollars building sea walls to prevent that from happening.

More Valley Glacier Features

Last week, we saw a brief time-lapse video of glacial ice moving down a slope. It could be easily seen that the ice was considerably broken up. That is because of the contour of the land underneath. Not all land under glaciers is like that. As valley glaciers move down mountains, there can be considerable areas that are fairly flat. The ice still moves over those areas, slowly, because it is being pushed and pulled down by ice above and below. But flat or not, the ice still moves. In those areas, it is relatively safe for people to walk around on top. However, relatively safe is not the same as perfectly safe. 

Ice on top of glaciers is brittle and is easily broken up from even even modest unevenness in the land underneath. Ice toward the sides of valley glaciers moves more slowly than ice in the middle. These factors can cause crevasses to open up in the ice.

 Though there might be initial resistance, the brittle nature of surface glacial ice can result in sudden openings occurring, Areas that have been carefully mapped for safe routes one day can be extremely hazardous the next. Crevasses may be hidden under newly fallen snow. The sides of old crevasses might be connected by snow bridges.

Snow bridges are always risky to cross. One that is substantial enough to support the weight several people crossing one at a time can suddenly give way for the next person. Well trained and prepared mountaineers who plan on crossing glaciers are always roped together and carry specialty equipment, including ice axes. 

Ice axes have several features to help break falls and assist people to climb ice cliffs, including the sides of crevasses if one survives a fall into one.

Crampons, those spiky things this person has on his boots, are extremely helpful, too.

Another interesting feature of some glaciers is an ice cave.

Polar Ice Caps

The Earth has two polar ice caps. One sits on Antarctica and is not going away, at least not totally, for a long time if ever. The other one, at the North Pole, does not sit on land. It floats on the Arctic Ocean. Because of that, it is not a glacier, but it is worth mentioning anyway. The North Polar Ice Cap is disappearing because of global warming. The image below shows what the difference of 32 years has made.

Eagles

The inspiration for this week's painting subject was an Alaskan Inside Passage cruise I took this summer. Glaciers were among the highlights of the cruise, but along with them were stunning landscapes, cultural learning opportunities, and animals; especially animals. Among them were humpback whales, sea otters, and orcas.

We saw all of these animals and more on our trip, but the only photo or ours above is the sea otter. 

Some of the most thrilling sightings were bald eagles. These photos were among ones that we took.

The bald eagle is a type of sea eagle. Its body feathers are brown, and it has white head and tail feathers. It isn't really bald. It got the name from an old meaning for bald which was having white on the face and head. The bald eagle's range stretches from Alaska and Canada to the continental United States and northern Mexico.

Bald eagles live mainly by fishing. When zooming in to catch dinner, its talons face forward.

A quick grab with needle sharp talons and away it goes to feed the family.

Bald eagles mate for life. The pair look alike except that the female is 25% larger than the male.

They build the largest nests of any North American bird, and the largest tree nests of any animal. Nests weigh up to 2,200 pounds.

Egg laying usually occurs in late February, and hatching occurs from mid-April to early May.

For the first 4 to 5 weeks, males bring most of the food to nests. After that, females equally share in the chore until late in the nesting period when females take over almost entirely.

Mating begins at 4 to 5 years of age.

Habitat destruction, hunting, and especially DDT brought bald eagles close to extinction by the mid-20th century. DDT was a widely used insecticide that entered the food chain of many birds and animals with devastating results. Among its effects, it caused egg shells to become so thin that they were often crushed by the weight of incubating parents. There were only 417 nesting pairs left in the U.S.'s lower 48 states by 1963. 

The passage of environmental protection laws and the banning of DDT in 1972 came to the rescue. Bald eagles were listed as an endangered species until 1995 when their status was changed to threatened. They were delisted entirely in 2007 because of a remarkable comeback. As of a 2018 to 2019 census, there was a total of 316,700 individual bald eagles, including 71,467 nesting pairs, in the lower 48 states.

It would have been a shame for America's national symbol to go extinct. It achieved that status in 1782 when it was placed in the Great Seal of the United States.

Artwork

Katsushika Hokusai (1760 – 1849)

One of his last works, Hokusai's Eagle in a Snowstorm was painted on paper with gansai and gojun (color and white paint) in 1848.