Friday, August 9, 2019

'The Big Thaw' - melting glaciers and disappearing ground water

National Geographic reports on the big picture in The Big Thaw. As the climate warms, how much, and how quickly, will Earth’s glaciers melt?

Everywhere on Earth ice is changing. The famed snows of Kilimanjaro have melted more than 80 percent since 1912. Glaciers in the Garhwal Himalaya in India are retreating so fast that researchers believe that most central and eastern Himalayan glaciers could virtually disappear by 2035. Arctic sea ice has thinned significantly over the past half century, and its extent has declined by about 10 percent in the past 30 years. NASA’s repeated laser altimeter readings show the edges of Greenland’s ice sheet shrinking. Spring freshwater ice breakup in the Northern Hemisphere now occurs nine days earlier than it did 150 years ago, and autumn freeze-up ten days later. Thawing permafrost has caused the ground to subside more than 15 feet (4.6 meters) in parts of Alaska. From the Arctic to Peru, from Switzerland to the equatorial glaciers of Man Jaya in Indonesia, massive ice fields, monstrous glaciers, and sea ice are disappearing, fast.

Here are some examples of our melting planet and the consequences for human existence. 538’s significant digits email leads.

1/4 of Earth’s population
A quarter of the human population of our planet is facing the growing and dire risk of running out of water, according to World Resources Institute data published this week. Seventeen countries are under “extremely high water stress,” meaning they are already using nearly all the water they have. Several large cities — including São Paulo, Chennai and Cape Town — have recently experienced “acute shortages” of water. [The New York Times]

Read more in the Times’ report, A Quarter of Humanity Faces Looming Water Crises. Here is some.

Many [of those 17] are arid countries to begin with; some are squandering what water they have. Several are relying too heavily on groundwater, which instead they should be replenishing and saving for times of drought.

In those countries are several big, thirsty cities that have faced acute shortages recently, including São Paulo, Brazil; Chennai, India; and Cape Town, which in 2018 narrowly beat what it called Day Zero — the day when all its dams would be dry.

Groundwater is going fast

Mexico’s capital, Mexico City, is drawing groundwater so fast that the city is literally sinking. Dhaka, Bangladesh, relies so heavily on its groundwater for both its residents and its water-guzzling garment factories that it now draws water from aquifers hundreds of feet deep. Chennai’s thirsty residents, accustomed to relying on groundwater for years, are now finding there’s none left. Across India and Pakistan, farmers are draining aquifers to grow water-intensive crops like cotton and rice.

On top of agricultural and (increasing?) residential use, the proposed Rosemont mine, if ultimately approved, will suck more water from our own aquifer.

More stress in the forecast

Today, among cities with more than 3 million people, World Resources Institute researchers concluded that 33 of them, with a combined population of over 255 million, face extremely high water stress, with repercussions for public health and social unrest.

By 2030, the number of cities in the extremely high stress category is expected to rise to 45 and include nearly 470 million people.

Check out the graphic.

Water stress projections

How to fix the problem?

The stakes are high for water-stressed places. When a city or a country is using nearly all the water available, a bad drought can be catastrophic.

[For example:] After a three-year drought, Cape Town in 2018 was forced to take extraordinary measures to ration what little it had left in its reservoirs. That acute crisis only magnified a chronic challenge. Cape Town’s 4 million residents are competing with farmers for limited water resources.

A lot can be done to improve water management, though.

First, city officials can plug leaks in the water distribution system. Wastewater can be recycled. Rain can be harvested and saved for lean times: lakes and wetlands can be cleaned up and old wells can be restored. And, farmers can switch from water-intensive crops, like rice, and instead grow less-thirsty crops like millet.

“Water is a local problem and it needs local solutions,” said Priyanka Jamwal, a fellow at the Ashoka Trust for Research in Ecology and the Environment in Bangalore.

The Washington Post reports that Greenland is on track for a record melt year, having already lost 250 billion tons of ice. Arctic sea ice is also at a record low as a warmer-than-average summer takes its toll. And other glaciers around the world are receding rapidly.

According to the National Snow and Ice Data Center (NSIDC) in Boulder, Colo., Greenland has already lost a total of over 250 billion tons from a combination of melt runoff and low total snowfall earlier in the season. That’s enough to fill more than 90 million Olympic-size swimming pools. Or to put it another way, that much water could sustain the global population’s water intake for more than 40 years.

"The glacier flow system also contributes to loss, and will likely add another 60 to 100 billion tons of loss [as icebergs],” said Ted Scambos, a senior research scientist at the University of Colorado.

According to Scambos, 2012 eventually reached 300 billion tons of surface ice mass loss from Greenland. The rate of ice loss in Greenland has increased sixfold since the 1980s, according to a recent study, with the ice sheet responsible for raising global sea levels by 13.7 millimeters since 1972, half of which occurred in just the past 8 years.

And on top of that, reports the Post:

As of this week, there is no sea ice off the shores of Alaska, something that has never occurred before so early in the melt season. Ice has even pulled back again from the coastal waters north of Greenland, which had long been a refuge for the oldest and thickest ice cover. This was first seen in 2018, and no longer appears to be a fluke.

The rate and extent of present-day sea ice loss is unprecedented in at least 1,500 years, according to a 2017 report.

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