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The water cycle and atmospheric rivers

From NOAA, National Oceanic and Atmospheric Administration

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.


Image from NOAA, National Oceanic and Atmospheric Administration

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 river

from the NOAA website

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.

Atmospheric River GIF

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.

North America from space

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.





Protecting New Orleans from rising water levels

New Orleans, Louisiana

This is a placeholder blogpost. The article is to be written

New Orleans canal gates flood control

Map: Google Maps. Photos by Mary Grace McKernan; infographic: by Marc Fusco.


New Orleans Lake Pontchartrain Elevation map to Mississippi River

Image by Midnightcomm for Wikipedia, public domain.


Apps & Interactive graphics

Louisiana’s Sea Level Is Rising: SeaLevelRise.org



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

Fortified But Still In Peril, New Orleans Braces for Its Future

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

After a $14-Billion Upgrade, New Orleans’ Levees Are Sinking. Scientific American

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.

Rising Sea Levels May Limit New Orleans Adaptation Efforts. Scientific American

Fortified but still in peril, New Orleans braces for its future: Our Drowning Coast. By Mark Schleifstein | Posted February 24, 2018.

Fortified but still in peril, New Orleans braces for its future

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.

Rising sea to displace 500,000 New Orleans area residents, study says. NOLA.com

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.

Migration induced by sea-level rise could reshape the US population landscape (Nature, science journal)


Sea level rise

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.

Global Average sea level

Global mean sea level data from the Colorado University Sea Level Research Group, with 4-to-5-year linear trends shown in black and red. Illustration: Dana Nuccitelli

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.

amount of ice loss across Antarctica

The amount of ice loss across Antarctica in total (purple), and in West Antarctica (green), East Antarctica (yellow) and the Antarctic Peninsula (red). Illustration: Shepherd et al. (2018), Nature

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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If all land ice melted how would coastlines change

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:


sea rise GIF Influence of tidal-range change and sediment compaction on Holocene relative sea-level change in New Jersey,

HORTON, B. P., ENGELHART, S. E., HILL, D. F., KEMP, A. C., NIKITINA, D., MILLER, K. G. and PELTIER, W. R. (2013), Influence of tidal-range change and sediment compaction on Holocene relative sea-level change in New Jersey, USA. J. Quaternary Sci., 28: 403–411

If This GIF of 10,000 Years of Sea Level Rise Doesn’t Freak You Out, Nothing Wil


Boston underwater: How the rising sea levels will affect the city


What Could Disappear. New York Times Sunday Review.


“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

Map 1

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.

Ice melt north america

Map 2

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.

Ice melt South America

Map 3

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.

Ice melt Europe

Map 3

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.

Ice melt Asia


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.

Ice melt Antarctica

All maps by: Jason Treat, Matthew Twombly, Web Barr, Maggie Smith, NGM Staff. Art Kees Veenebos. From Sept. 2013 National Geographic Society

What the World Would Look Like if All the Ice Melted (National Geographic)


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