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The water cycle is often taught as a simple circular cycle of evaporation, condensation, and precipitation.
Although this can be a useful model, the reality is much more complicated. The paths and influences of water through Earth’s ecosystems are extremely complex and not completely understood.
Liquid water evaporates into water vapor, condenses to form clouds, and precipitates back to earth in the form of rain and snow.
Water in different phases moves through the atmosphere (transportation).
Liquid water flows across land (runoff), into the ground (infiltration and percolation), and through the ground (groundwater).
Groundwater moves into plants (plant uptake) and evaporates from plants into the atmosphere (transpiration).
Solid ice and snow can turn directly into gas (sublimation).
The opposite can also take place when water vapor becomes solid (deposition).
Atmospheric rivers are relatively long, narrow regions in the atmosphere – like rivers in the sky – that transport most of the water vapor outside of the tropics.
These columns of vapor move with the weather, carrying an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River. When the atmospheric rivers make landfall, they often release this water vapor in the form of rain or snow.
Although atmospheric rivers come in many shapes and sizes, those that contain the largest amounts of water vapor and the strongest winds can create extreme rainfall and floods, often by stalling over watersheds vulnerable to flooding.
These events can disrupt travel, induce mudslides and cause catastrophic damage to life and property.
A well-known example is the “Pineapple Express,” a strong atmospheric river that is capable of bringing moisture from the tropics near Hawaii over to the U.S. West Coast.
Not all atmospheric rivers cause damage; most are weak systems that often provide beneficial rain or snow that is crucial to the water supply. Atmospheric rivers are a key feature in the global water cycle and are closely tied to both water supply and flood risks — particularly in the western United States.
New Orleans, Louisiana
This is a placeholder blogpost. The article is to be written
Apps & Interactive graphics
Fortified But Still In Peril, New Orleans Braces for Its Future: In the years after Hurricane Katrina, over 350 miles of levees, flood walls, gates and pumps came to encircle greater New Orleans. Experts say that is not enough.
By John Schwartz and Mark Schleifstein, 2/24/2018
After a $14-Billion Upgrade, New Orleans’ Levees Are Sinking. Sea level rise and ground subsidence will render the flood barriers inadequate in just four years. By Thomas Frank, E&E News, Scientific American, 4/11,/2019
Rising Sea Levels May Limit New Orleans Adaptation Efforts. New Orleans sees that even modern engineering cannot eliminate flooding risk. By Emily Holden, ClimateWire on September 10, 2015. Scientific American.
Fortified but still in peril, New Orleans braces for its future: Our Drowning Coast. By Mark Schleifstein | Posted February 24, 2018.
Rising sea to displace 500,000 New Orleans area residents, study says; see where they might go. By Tristan Baurick, NOLA.com | The Times-Picayune. 4/20/2017.
A study published this week (April 2017) predicts that sea level rise will push hundreds of thousands of people out of U.S. coastal cities such as New Orleans. It says the population will boom in nearby inland cities such as Austin. The University of Georgia study is considered the first detailed look at how inland cities might be affected by sea level rise. It estimates more than than 500,000 people will flee the seven-parish New Orleans area by 2100 due to sea level rise and the problems that come with it, including frequent flooding and greater exposure to storm surges. That’s more than one third of metro New Orleans’s current population…. Across the United States, the study estimates, 13 million people will be displaced by sea level rise under a scenario in which some efforts are taken to mitigate the impacts of sea level rise. The biggest draw, it predicts, will be Austin, gaining 600,00 to 800,000 people on top of the metro area’s current estimated population of 2.1 million. Other inland cities likely to grow substantially include Orlando, Fla., Atlanta and Phoenix.
Migration induced by sea-level rise could reshape the US population landscape
Mathew E. Hauer. Nature Climate Change volume 7, pages 321–325 (2017)
Many sea-level rise (SLR) assessments focus on populations presently inhabiting vulnerable coastal communities, but to date no studies have attempted to model the destinations of these potentially displaced persons. With millions of potential future migrants in heavily populated coastal communities, SLR scholarship focusing solely on coastal communities characterizes SLR as primarily a coastal issue, obscuring the potential impacts in landlocked communities created by SLR-induced displacement. Here I address this issue by merging projected populations at risk of SLR with migration systems simulations to project future destinations of SLR migrants in the United States. I find that unmitigated SLR is expected to reshape the US population distribution, potentially stressing landlocked areas unprepared to accommodate this wave of coastal migrants—even after accounting for potential adaptation. These results provide the first glimpse of how climate change will reshape future population distributions and establish a new foundation for modelling potential migration destinations from climate stressors in an era of global environmental change.
Ever wonder what the Earth looked like before humans came along?
The 3D interactive website called Ancient Earth Globe lets you glimpse the world from space during the age of the dinosaurs — and more. Seeing the Earth at various points in geological history, from 750 million years ago to today, is an eye-opening activity to say the least. The website allows you to see the entire globe as it slowly rotates, or zoom in to see closer details of land and oceans. There’s also an option to remove clouds for an even better look.
(Text by Bonnie Burton, Cnet, 8/7/18, See what Earth looked like from space when it was ruled by dinosaurs)
Should we be worried about surging Antarctic ice melt and sea level rise?
Dana Nuccitelli, The Guardian, 18 Jun 2018
There’s recently been a spate of sea level rise denial in the conservative media, but in reality, sea level rise is accelerating and melting ice is playing an increasingly large role. In the first half of the 20th Century, average global sea level rose by about 1.4 millimeters per year (mm/yr). Since 1993, that rate has more than doubled to 3.2 mm/yr. And since 2012, it’s jumped to 4.5 mm/yr.
Thermal expansion (ocean water expanding as it warms) continues to play the biggest role in sea level rise, but its contribution of about 1.3 mm/yr is now responsible for a smaller proportion of total sea level rise (30% in recent years) than its contribution since the 1990s (40% of the total). That’s because of the acceleration in melting ice.
Glacier melt is accelerating, recently contributing about 0.75 mm/yr to sea level rise, up from 0.65 mm/yr since the 1990s. But the biggest jumps have come from ice in Greenland and Antarctica. Greenland had been responsible for about 0.48 mm/yr sea level rise since 1990, but in recent years is up to 0.78 mm/yr. A recent study in Nature Climate Change found that Greenland contributed about 5% to sea level rise in 1993 and 25% in 2014.
Antarctica is a huge question mark with warning signs
A new study published in Nature using data from a range of satellites found that Antarctica’s contribution has tripled from about 0.2 mm/yr since the 1990s to 0.6 mm/yr since 2012, during which time global sea level rise also spiked. Accelerated ice melt from Antarctica, Greenland, and glaciers have all played a role in the faster recent sea level rise. The question is whether it’s a temporary jump, or if we need to worry about a continued acceleration in Antarctic ice loss.
Another recent paper published in Earth’s Future found that rapid losses from Antarctic ice are plausible. The study found that in moderate to high carbon-emission scenarios, an average expected sea level rise of 2 to 2.5 feet by 2100 could actually become 3 to 5 feet once Antarctic ice sheet dynamics are taken into account.
The vast majority of Antarctica’s current ice loss is coming from West Antarctica, where about 75% of the glaciers are located below sea level. In East Antarctica, which has so far remained stable, only about 35% of the glaciers are below sea level. Warming ocean waters are melting the Antarctic ice from below, which is particularly problematic for that low-lying ice in West Antarctica. Research suggests that the collapse of the Western Antarctic ice sheet is already unstoppable.
Should we be worried?
Short term variations in sea level rise do happen. Sea level actually briefly fell in 2010 due to a strong La Niña cycle, which typically results in an increase of rain and snow falling over land. This resulted in a number of epic deluges and flooding across the globe; more water on land temporarily meant less in the ocean.
However, Antarctica and Greenland could potentially cause rapid sea level rise. As James Hansen explains in the video below, there have been periods in the not-so-distant past when sea levels rose at an average rate of 1 meter every 20 years.
In past eras when temperatures and atmospheric carbon dioxide levels were similar to those today and to the Paris climate targets, like in the last interglaciation and the Pliocene, sea levels were about 20 to 80 feet higher. Unless we manage to actually cool global temperatures, we’re certainly due for significantly more sea level rise. The large ice sheets on Greenland and Antarctica will continue to melt for as long as 1,000 years. That’s why sea levels were so much higher in past eras whose climates remained at hot temperatures like today’s for thousands of years.
It takes time for ice to melt. The question is, how fast will it happen? Sea level rise unquestionably poses a long-term threat, but how much of a short-term threat largely depends on just how stable the Antarctic ice sheet turns out to be. The recent acceleration of Antarctic ice loss, while not yet definitive, is certainly cause for concern.
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§107. Limitations on Exclusive Rights: Fair Use. Notwithstanding the provisions of section 106, the fair use of a copyrighted work, including such use by reproduction in copies or phone records or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use, the factors to be considered shall include: the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes; the nature of the copyrighted work; the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and the effect of the use upon the potential market for or value of the copyrighted work. (added pub. l 94-553, Title I, 101, Oct 19, 1976, 90 Stat 2546)
This analysis is by Phil Plait, Mar 9, 2017
I will ask you to indulge me for a moment in a thought experiment. It’s not hard, and it leads to a startlingly simple yet powerful conclusion, one I think you may find both important and terribly useful.
Still, it starts with a big ask, so forgive me. And that is: Let’s make an assumption, one you’ve heard many times before. Let’s say that global warming is a hoax.
I know, I know. But go with this, here. So, yes, let’s say that climate change deniers —people like House Science, Space, and Technology Committee chairman Lamar Smith, Senator James Inhofe, and even Donald Trump himself— are right. Whatever the reasons (Chinese hoax, climatologist cabal clamoring colossal cash, carbon dioxide isn’t a powerful greenhouse gas, or just a liberal conspiracy), let’s say that the Earth is not warming up.
In that case, the temperatures we see today on average should be much like the ones we saw, say, 20 years ago. Or 50. Sure, you’d see fluctuations. In a given spot on a given day the temperature in 1968 might have been a degree warmer than it was in 1974, or three degrees cooler than in 2010. But what you’d expect is that over time, a graph showing the temperature would be pretty much flat, with lots of short-term spikes up and down.
Now, statistically speaking, you expect some records to be broken every now and again. Over time, every few years for a given day you’d get a record high, and every few years a record low. The details will change from place to place and time to time, but again, if the average temperature trend is flat, unchanging, then you would expect to see just as many record cold days as record warm days. There might be small deviations, like, say, a handful of more cool than warm days, but the difference would be very small depending on how many days you look at.
It’s like flipping a coin. On average, you should get a 50/50 split between heads and tails. But if you flip it 10 times, say, you wouldn’t be shocked to see seven heads and three tails. But if you flip it a thousand times, you’d really expect to see a very even split. Seeing 700 heads and 300 tails would be truly extraordinary.
So, if we remind ourselves of our basic assumption —global warming isn’t real— then we expect there to be as many record high days as there are record lows. Simple statistics.
So, what do we see?
Guy Walton, a meteorologist in Georgia, took a look at the data from the NOAA’s National Centers for Environmental Information. Whenever a weather station in the US breaks a record, high or low, it’s catalogued (Walton has more info on this at the link above). He found something astonishing: For February 2017, the number of record highs across the US recorded was 6,201.
The number of record lows? 128.
That’s a ratio of over 48:1. In just one month.
Again, if temperatures were flat over time, and record highs and lows were random fluctuations, you’d expect a ratio much closer to 1:1. In other words, out of 6329 records set in total, you’d expect there to be about 3165 record highs, and 3165 record lows.
For fans of statistics, with a total of 6329 records broken, one standard deviation is the square root of that, or about 80. So, sure, something like 3265 highs and 3064 lows wouldn’t be too unusual. If you start to see more of an imbalance than that, it would be weird.
Seeing 6201 record highs to 128 lows is very, very, very weird. Like, zero chance of that happening by accident.
Now, Phil, I can hear you thinking, that’s just for the US (2% of the planet) over one month. And you’ve told us before that weather isn’t climate; weather is what you expect now, climate is what you expect over long periods of time. So, maybe this is a fluke?
Walton notes that, if you look at records in the US going back to the 1920s, the six highest ratios of record highs to lows all occur since the 1990s. Huh.
And making this more global, a pair of Australian scientists looked at their country’s data, and found that their ratios were about even…until the 1960s. After that, highs always outnumber lows. From 2000-2014, record highs outnumbered lows there by 12:1.
The University Corporation for Atmospheric Research collated data from 1800 stations across the US and binned the data by decade — by decade, which is a huge sample; any deviation from a 1:1 ratio would be extraordinary over that timescale.
Source of the above image: RECORD HIGH TEMPERATURES FAR OUTPACE RECORD LOWS ACROSS U.S. The National Center for Atmospheric Research/UCAR, Nov 12, 2009
We are seeing far more record high temperatures than record lows in the US… and in other countries, too. Credit: UCAR
Huh. Not only are there more record highs than lows, the ratio between the two is getting higher with time.
So, looking back at our initial assumption — the Earth isn’t warming, and temperatures are flat— there’s a conclusion these data are screaming at us: That assumption is completely and utterly wrong.
And of course, all the evidence backs this up. All of it. Earth’s temperature is increasing. That’s because of the 40 billion tons of extra carbon dioxide humans put into the atmosphere every year (the amount we will see this year, expected to top 410 parts per million, has never been seen before in history as long as humans have walked the Earth). This CO2 allows sunlight to warm the Earth, but prevents all of it from escaping so that a little bit of extra heat remains behind, and that’s warming our planet.
Over time, we’re getting hotter. 2014 was a record hot year, beaten by 2015, itself beaten by 2016. In fact, 15 of the 16 hottest years ever recorded have been from 2001 – 2016. That’s exactly what you’d expect if we were getting warmer, and that means our initial assumption of hoaxery was dead wrong.
The science on this is so basic, the evidence of this so overwhelming, that “not a single national science academy disputes or denies the scientific consensus around human-caused climate change”, and also the overwhelming majority of scientists who study climate do, too.
Maybe you should listen to them, and not politicians who seem ideologically opposed to the science.
Or, you could flip a coin. But if it comes up science dozens of times more often than anti-science, well —and forgive me if I sound like a broken record— the conclusion is obvious.
Fair use: This website is educational. Materials within it are being used in accord with the Fair Use doctrine, as defined by United States law.
§107. Limitations on Exclusive Rights: Fair Use
Notwithstanding the provisions of section 106, the fair use of a copyrighted work, including such use by reproduction in copies or phone records or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use, the factors to be considered shall include: the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes; the nature of the copyrighted work; the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and the effect of the use upon the potential market for or value of the copyrighted work. (added pub. l 94-553, Title I, 101, Oct 19, 1976, 90 Stat 2546)
Protecting cities from rising sea levels
from “Can New York Be Saved in the Era of Global Warming?” by Jeff Goodell, Rolling Stone, July 2016.
Hurricane Sandy, which hit New York in October 2012, flooding more than 88,000 buildings in the city and killing 44 people, was a transformative event. It did not just reveal how vulnerable New York is to a powerful storm, but it also gave a preview of what the city faces over the next century, when sea levels are projected to rise five, six, seven feet or more, causing Sandy-like flooding (or much worse) to occur with increasing frequency.
Zarrilli turns away from the river, and we walk toward the park that separates it from the Lower East Side. “One of our goals is not just to protect the city, but to improve it,” Zarrilli explains. Next year, if all goes well, the city will break ground on what’s called the East Side Coastal Resiliency Project, an undulating 10-foot-high steel-and-concrete-reinforced berm that will run about two miles along the riverfront. It’s the first part of a bigger barrier system, known informally as “the Big U,” that someday may loop around the entire bottom of Manhattan… there are plans in the works to build other walls and barriers in the Rockaways and on Staten Island, as well as in Hoboken, New Jersey, across the Hudson River. …
…wall-building is politically fraught: You can’t wall off the city’s entire 520-mile coastline, so how do you decide who gets to live behind the wall and who doesn’t? “You have to start somewhere,” Zarrilli says, “so you begin in the places where you get the maximum benefit for the most people.”
In Zarrilli’s view, there is no time to waste. By 2030 or so, the water in New York Harbor could be a foot higher than it is today. That may not sound like much, but New York does not have to become Atlantis to be incapacitated. Even with a foot or two of sea-level rise, streets will become impassable at high tide, snarling traffic. …
Then the big storm will come… if you add a foot or two of sea-level rise to a 14-foot storm tide, you have serious trouble. …Water will flow over the aging sea walls at Battery Park and onto the West Side, pouring into the streets, into basements, into cars, into electrical circuits, finding its way into the subway tunnels. New Yorkers will learn that even after the region spent $60 billion on rebuilding efforts after Sandy, the city’s infrastructure is still hugely vulnerable.
… New York’s Achilles’ heel is the subways, which are vulnerable to saltwater, which is highly corrosive to electrical circuits, as well as to the concrete in the tunnels. In theory, the subway system can be restructured to keep seawater out, but at some point, the cost gets prohibitive. … the Metropolitan Transportation Authority, which operates the New York subways, had to spend $530 million upgrading the South Ferry station in Lower Manhattan after it was heavily damaged on 9/11. After Sandy turned the station into a fish tank, the MTA had to close it for months and spend another $600 million to fix it. The MTA has now installed retractable barriers to stop seawater from flooding the station in the next big storm, but the subway system remains vulnerable to rising seas. “We’re not thinking systemically about climate change,” says Michael Gerrard, director of the Center for Climate Change Law at Columbia Law School. “We’re focused on Sandy, and Sandy isn’t the worst thing that could happen.”
In the end, there is only one real solution for sea-level rise: moving to higher ground.
In the near future, one of the main drivers of what policy wonks call “managed retreat” is likely to be the rising costs of flood insurance, which is provided to most property owners through National Flood Insurance Protection, an outdated, mismanaged federal program that subsidizes insurance rates for homeowners and businesses in high-risk areas (commercial insurers bailed out of the flood-insurance market decades ago).
Under NFIP, few people who live in flood-prone areas pay the actual cost of the risk. In addition, grandfather clauses in the program often allow homeowners to rebuild in areas that are doomed to flood again very soon. Attempts by Congress to reform the program have failed miserably, and it’s now $23 billion in debt. Eventually, increasing property losses will force reform and insurance rates will go up and up. “When people have to pay more and own more of the risk themselves, their decisions about where they live will change,” says Alex Kaplan, a senior vice president at Swiss Re, a global reinsurance company.
New York state is already experimenting with voluntary buyouts in high-risk areas. The logic is simple: In the long run, it’s cheaper simply to buy people out of their homes than to keep paying for them to be rebuilt after storms (it also moves people out of harm’s way).
Of course, it would cost hundreds of billions of dollars to buy out residents and businesses in Lower Manhattan. Instead, some urban planners have discussed offering tax breaks and other financial goodies to encourage residents and businesses to relocate to higher ground. Could parts of Lower Manhattan ever be de-populated and returned to nature? “Buildings were built,” says Kate Orff, director of the urban-planning program at Columbia University’s Graduate School of Architecture, Planning and Preservation. “They can also be unbuilt.” More likely, the walls will go up, getting higher and higher as the seas rise.
The above info is from https://www.rollingstone.com/politics/news/can-new-york-be-saved-in-the-era-of-global-warming-20160705#ixzz4Da26LKLM
Protecting Staten Island, New York City
Topic: Staten Island Multi-Use Elevated Promenade
This text from the article “A 5.3-Mile “Elevated Promenade” On Staten Island Will Break Ground This Year” by Bianca Bahmondes, Secret NYC, 2/25/2019
It was recently announced that the 5.3-mile proposed seawall in Staten Island will officially begin construction since federal funding has now been secured. The U.S. Army Corps for Engineers (USACE) will be giving $400 million to the project, which is formally known as the Staten Island Multi-Use Elevated Promenade. This new promenade has been in the works since 2015 and is intended to help protect the island from sea-level rising, storm surges, and super storms in the future.
It will be build along the island’s eastern coast from Fort Wadsworth to Great Kills. The promenade will rise about 20 feet above sea level and feature a series of interconnected leaves, berms, and seawalls that are designed to withstand a 300-year storm.
In the announcing statement Governor Cuomo said: “This innovative project will protect Staten Islanders from future devastating storms, enhance access to the shore, create thriving wetlands and bring peace of mind to the diverse communities that live along the coastline. [This] agreement allows New York to move forward with this critical resiliency measure, which will ensure vulnerable communities have the resources they need to build back stronger after the devastation of Hurricane Sandy and better prepare for the next 100-year storm.”
HS-ESS2-6. Use a model to describe cycling of carbon through the ocean, atmosphere, soil, and biosphere and how increases in carbon dioxide concentrations due to human activity have resulted in atmospheric and climate changes.
HS-ESS3-1. Construct an explanation based on evidence for how the availability of key natural resources and changes due to variations in climate have influenced human activity.
HS-LS2-7. Analyze direct and indirect effects of human activities on biodiversity and ecosystem health, specifically habitat fragmentation, introduction of non-native or invasive species, overharvesting, pollution, and climate change. Evaluate and refine a solution for reducing the impacts of human activities on biodiversity and ecosystem health.*
High School Technology/Engineering
HS-ETS1-1. Analyze a major global challenge to specify a design problem that can be improved. Determine necessary qualitative and quantitative criteria and constraints for
solutions, including any requirements set by society.*
HS-ETS1-2. Break a complex real-world problem into smaller, more manageable problems that each can be solved using scientific and engineering principles.*
HS-ETS1-3. Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, aesthetics, and maintenance, as well as social, cultural, and environmental impacts.*
Scientists have used evidence to reconstruct sea-level rise around America’s northeast coast over the last 10,000 years.
New Jersey going back 10,000 years in research newly published in the Journal of Quaternary Science. To do this, they collected sediment cores drilled tens of meters below ground from coastal marshes, then examined the sediment back in a lab for microscopic organisms that only exist at specific depths below sea level. Salt marsh grasses also fossilized within the sediment were used to radiocarbon-date the samples.
The 10 maps contained in the GIF below show the movement of sea level at 1,000-year intervals leading up today:
“If we keep burning fossil fuels indefinitely, global warming will eventually melt all the ice at the poles and on mountaintops, raising sea level by 216 feet. Explore what the world’s new coastlines would look like.
“The maps here show the world as it is now, with only one difference: All the ice on land has melted and drained into the sea, raising it 216 feet and creating new shorelines for our continents and inland seas.
There are more than five million cubic miles of ice on Earth, and some scientists say it would take more than 5,000 years to melt it all. If we continue adding carbon to the atmosphere, we’ll very likely create an ice-free planet, with an average temperature of perhaps 80 degrees Fahrenheit instead of the current 58.”
from National Geographic Magazine, What the World Would Look Like if All the Ice Melted
The entire Atlantic seaboard would vanish, along with Florida and the Gulf Coast. In California, San Francisco’s hills would become a cluster of islands and the Central Valley a giant bay. The Gulf of California would stretch north past the latitude of San Diego—not that there’d be a San Diego.
The Amazon Basin in the north and the Paraguay River Basin in the south would become Atlantic inlets, wiping out Buenos Aires, coastal Uruguay, and most of Paraguay. Mountainous stretches would survive along the Caribbean coast and in Central America.
London? A memory. Venice? Reclaimed by the Adriatic Sea. Thousands of years from now, in this catastrophic scenario, the Netherlands will have long since surrendered to the sea, and most of Denmark will be gone too. Meanwhile, the Mediterranean’s expanding waters will also have swelled the Black and Caspian Seas.
Land now inhabited by 600 million Chinese would flood, as would all of Bangladesh, population 160 million, and much of coastal India. The inundation of the Mekong Delta would leave Cambodia’s Cardamom Mountains stranded as an island.
East Antarctica: The East Antarctica ice sheet is so large—it contains four-fifths of all the ice on Earth—that it might seem unmeltable. It survived earlier warm periods intact. Lately it seems to be thickening slightly—because of global warming. The warmer atmosphere holds more water vapor, which falls as snow on East Antarctica. But even this behemoth is unlikely to survive a return to an Eocene Climate.
West Antarctica: Like the Greenland ice sheet, the West Antarctic one was apparently much smaller during earlier warm periods. It’s vulnerable because most of it sits on bedrock that’s below sea level.The warming ocean is melting the floating ice sheet itself from below, causing it to collapse. Since 1992 it has averaged a net loss of 65 million metric tons of ice a year.
All maps by: Jason Treat, Matthew Twombly, Web Barr, Maggie Smith, NGM Staff. Art Kees Veenebos. From Sept. 2013 National Geographic Society