September 19, 2017, 08:25 PDT

Weather or climate change?

From NASA’s Global Climate Change website team

A pre-winter storm located just off the coast of southwestern Australia was photographed from the International Space Station on March 29, 2014. A solar array panel on the orbital outpost is in the left side of the frame.

A pre-winter storm located just off the coast of southwestern Australia was photographed from the International Space Station on March 29, 2014. A solar array panel on the orbital outpost is in the left side of the frame.

One query we frequently get from the public is to explain the difference between weather and climate. It’s a great question.

Some people say “weather is what you get” and “climate is what you expect.” In a nutshell, “weather” refers to the more local changes in the climate we see around us, on short timescales from minutes to hours to days to weeks. Examples are familiar – rain, snow, clouds, winds, storms, heat waves and floods. “Climate” refers to longer-term averages (they may be regional or global), and can be thought of as the weather averaged over several seasons, years or decades. Climate change is harder for us to get a sense of because the timescales involved are much longer, and the impact of climate changes can be less immediate. 

Dr. Eric Fetzer, a scientist at NASA’s Jet Propulsion Laboratory, explains it this way: “Weather describes how the atmosphere behaves over weeks or less. Climate is how it behaves over time periods of about a month or longer. So climate refers to seasonal and longer periods, out to centuries and millennia.”

In addition to long-term climate change, there are shorter term climate variations. This so-called climate variability can be represented by periodic or intermittent changes related to El Niño, La Niña, volcanic eruptions, or other changes in the Earth system.

As always, we welcome your questions and comments.

August 7, 2017, 10:31 PDT

The next big question in sea level science

Projecting regional changes

By Laura Faye Tenenbaum

Lower Manhattan, where the Regional Sea Level Changes and Coastal Impacts Conference was held, lies within a few feet of sea level. Credit: NASA.

Lower Manhattan, where the Regional Sea Level Changes and Coastal Impacts Conference was held, lies within a few feet of sea level. Credit: NASA.

“Sea level scientists have a pretty good grasp on global mean sea level,” said Steve Nerem, a professor in the Aerospace Engineering Sciences Department at the University of Colorado and the team leader for NASA’s Sea Level Change Team (N-SLCT). “It’s the regional sea level change that’s the next big question, the next big step for sea level science,” he added.

Nerem and much of the rest of the N-SLCT were in New York City this July where more than 300 scientists from 42 countries gathered at Columbia University for a weeklong Regional Sea Level Changes and Coastal Impacts Conference. The international conference was organized by the World Climate Research Programme (WCRP), Climate and Ocean – Variability, Predictability, and Change (CLIVAR), and the UNESCO Intergovernmental Oceanographic Commission and was co-sponsored by NASA.

Regional sea level change is more variable, over both space and time, than global sea level change and can diverge by up to 7 inches (20 centimeters) or more from the global mean. Additionally, making regional projections about future sea level differs from making global mean sea level projections. This is due to the fact that different processes contribute to sea level change in coastal regions.

Global sea level rise is caused by thermal expansion of warmer water plus contributions from ice sheets and glaciers. Regional sea level change, especially along coastlines, is influenced by additional factors, including vertical land movements, waves and tides, and winds and storms. So in order to estimate sea level inundation and flood risk, scientists have to understand all the factors that contribute to extreme water levels such as local sea level rise, land subsidence, tides, waves and storm surge.

“Where I live, it’s hard to separate the pure science from the applications. With all this flooding, the broader significance of your work is very clear.”
- Ben Hamlington, upcoming NASA Sea Level Change Team leader

Members of the N-SLCT understand the importance of studying coastal sea level change and improving the accuracy of regional projections. Ben Hamlington, assistant professor in the Ocean, Earth and Atmospheric Sciences Department at Old Dominion University in Norfolk, Virginia, and upcoming team leader for N-SLCT is serious about understanding sea level.

“The overarching theme of my scientific research,” he said, is “to consistently improve regional sea level projections.” Manhattan, where the conference was held, for example, lies within a few feet of sea level, and furthermore, the U.S. East Coast has some of the highest amounts of projected sea level increase.

“Global means aren’t very useful for someone who’s on the coast of Virginia where I live,” Hamlington said. A main part of the challenge of predicting regional sea level is that what causes the sea level changes and the flooding varies dramatically from place to place. Hamlington described a term called “nuisance flooding,” which is a type of persistent tidal flooding that leads to public inconveniences like road closures and backed-up storm water systems.

“Basically it means your path to work has to change because a certain road is blocked or impassable. You can still get to work, but it might take longer,” he explained. Right now, these nuisance-flooding events occur multiple times a year. But as sea level continues to rise, the nuisance flooding will get more and more frequent and will become even more of a problem. “Where I live, it’s hard to separate the pure science from the applications. With all this flooding, the broader significance of your work is very clear,” he said.

In Norfolk, Virginia, glacial isostatic adjustment (GIA) is around 0.04 inches (1 millimeter) per year, another millimeter per year of subsidence is due to slow subsidence into the Chesapeake Bay Meteor Impact Crater plus ground water pumping. Finally add 0.08 inches (2 millimeters) per year from the ocean rising and “You get the long-term tide gauge rate of relative sea level rise of just lower than 0.20 inches (5 millimeters) per year over the last 100 years. That’s a pretty high rate of sea level rise over a long period of time,” Hamlington explained. “Beyond nuisance flooding, there are also extreme events,” he continued. “During a storm event, you can get several feet of water in some parts of Norfolk.”

Actionable science

Stakeholders and decision makers are the ones driving the demand for improved regional sea level projections, Hamlington continued. “They’re the ones driving the discussion toward regional projections and that’s what’s needed for planning efforts.” These stakeholders include state and local public works officers responsible for infrastructure such as stadiums, roads, seawalls, and dykes plus pumps, water utilities, other utilities, businesses, and coastal inhabitants.

Scientists are responsible for helping society. This is why decision makers and scientists have come together to co-produce actionable science, to discuss how to communicate and collaborate, and to ensure that sea level science is being understood by the adaptation community.

“This is one of the biggest sea level conferences that we’ve had, when everybody who is working in different areas of the field comes together,” said Nerem. There were presentations on a variety of techniques to measure sea level change: tide gauges, measurements in marshes, paleo-sea level, corals, but from the perspective of the N-SLCT, “ We’re really focused on how to use remote sensing, satellite altimetry from Jason-1, 2 and 3 and Gravity Recovery and Climate Experiment (GRACE) combined with GPS measurements to improve regional sea level measurements and projections.”

Nerem’s project targets regions around the globe that are susceptible to inundation but don’t have much measurement infrastructure, such as Bangladesh. Many of these regions do not have detailed digital elevation models or 50 years of tide gauge measurements like we do in the United States.  “If we use our satellite techniques and test them in a place we understand, then we can go out where we don’t have that infrastructure and assess future sea level change in those regions.”

The N-SLCT hopes to leverage the satellite observations as much as possible to try to better understand future regional sea level change. This will help decision makers, coastal managers and stakeholders better adapt and prepare for the impacts of sea level rise.

According to Nerem, “We would like to produce a new assessment of future regional sea level change that benefits from the extensive record of satellite measurements collected by NASA.”

Thank you for reading,

June 5, 2017, 09:31 PDT

Sun and sky, snow and ice

Reflections at the top of the world

By Laura Faye Tenenbaum

Hiking up to Greenland’s ice sheet, the sun remains low on the horizon even during midday.

Hiking up to Greenland’s ice sheet, the sun remains low on the horizon even during midday.

It was 11:30 in the morning and GLISTIN-A instrument engineer Ron Muellerschoen and I were in northern Greenland at the Thule Air Base pier looking over the frozen Wolstenholme Bay. We’d been talking about the time Ron was wearing shorts here during the summer, but today it was the typical -22 Fahrenheit (-30 Celsius.) And even though over the past week we’d somehow gotten used to the cold and I was wearing a big parka, my legs were starting to get cold after walking for an hour. So we decided to head back.

As we turned around to go, I was struck in the face by the sun’s rays reflecting off the ice-covered ground. The brightness was astounding. And in that instant the meaning of “albedo” was seared into my brain in a way that went beyond reading about the science or looking at illustrations and animations.

There was something special about the experience of having the rays of the sun, which was sitting low in the high latitude sky, hit the ice surface at that extremely low angle and reflect off into my eyes.

Albedo is a measure of how reflective a surface is, how much light energy bounces off and reflects away and how much light energy gets absorbed. (Think hot asphalt on a sunny day. Black asphalt has a low albedo and absorbs light energy, while the brightest white has the highest albedo and reflects the light.)

Walking in Greenland
Team Oceans Melting Greenland (OMG) stands on the Greenland Ice Sheet. Notice the long shadows made by small rocks on the ground.
Albedo is part of what has stabilized Earth’s climate for millennia, because under normal conditions, the white of the polar ice reflects light energy back to space, keeping average global temperature stable. The more area covered by ice, the more heat reflected back to space. The more ice that melts, the more heat absorbed. Increasing temperatures are melting more ice, which exposes darker brown and green land and dark blue ocean. Those darker surfaces have a lower albedo, so they absorb more of the heat from the sun’s rays.

I stood for a moment, looking at the ground — a hard, dry, crusty mixture of ice and snow that made an exceptionally satisfying crunch crunch noise as our boots marched through it — and tried to figure out the color: 50 shades of white. I settled on white/light blue/silvery sparkle. Due to the low angle of the sun, the tiniest rough edge the size and shape of a pebble on the ground’s textured surface left a long, dark shadow.

No matter where we were or how we stood or what time of day, all day, every day, there were always long shadows — crazy long shadows. At 78 degrees north latitude, a full 12 degrees above the Arctic Circle, the sun will never be overhead. Never. I know that seems unbelievable, but even during the summer solstice, when Earth’s North Pole is tilted toward the sun, or during the four summer months of 24-hour daylight, the sun is always low, low, low at this latitude.

Low on the horizon

In that moment, I also understood another science question that had been bothering me. I’d been wondering why the meter-thick sea ice hadn’t yet begun to melt. Even though it was the end of March, even though the equinox had passed, the sun was out and the days were getting longer. In fact, up here the days were getting much longer, very quickly. On March 23, just three days after the equinox, we were already having 14-hour days with sunsets lasting past 9 p.m. That’s because in these high latitudes, the day length can increase by as much as 40 minutes per day. And by mid-April, just a few weeks after spring equinox, there will be 24 hours of daylight and the sun won’t set again until September. 

By mid-April the meter-thick layer of frozen seawater that covers the sea surface and fills the fjords will completely melt and expose the dark blue ocean underneath. But today, even in this brilliant sunshine, even on this day of 14-hour sunlight, the ocean was still completely frozen over. 

Greenland ice
The sun sits low in the sky even during midday. This iceberg calved off one of Greenland's coastal glaciers, floated into Wolstenholme Fjord and then became trapped in sea ice.
Just the other day in fact, a group of us walked about 3 miles (5 kilometers) across the frozen ocean into the middle of Wolstenholme Fjord to visit icebergs trapped in the frozen seawater. We hadn't worried at all about breaking through. 

But “Why?” I’d been wondering. Why, with all this extra sunshine, was the sea surface still so frozen? And why did that hard, dry, crusty mixture of ice and snow still remain on the ground?

In that instant, as the glint of the sunlight reflecting off the icy ground hit my face, I knew exactly why. It was the extraordinarily low angle of the sunlight that bounced right off the stunning bright whiteness of the ice. The sunlight was not absorbed by the ice and snow and instead was reflected away. It wouldn’t be until another month or so that the sun would get a little higher in the sky. And although the sun would never be directly overhead up here, it would be high enough to begin melting the ice.

No matter how much a person studies Greenland, or the northern latitudes, or albedo, or Earth in general, going into the field to experience those things can change your entire understanding of the world and how it works. I stood there for a moment, just allowing the high-latitude sun’s cold rays to glance off the snowy ice and shine straight into my face.

NASA’s Oceans Melting Greenland (OMG) team is here in Greenland; here to find out specifically how much ice the island is losing due to warmer ocean waters around the coastline. There is almost no ocean data in remote places like this, but OMG is busy working to change that, studying the complex ocean processes that affect Greenland's coastline because gathering data is critical to understanding Earth’s complex climate. This information will help us understand the amount of sea level rise we're going to have around the world.

Thank you for reading,


May 15, 2017, 12:00 PDT

Are you ready to work?

Dive into a sea of Oceans Melting Greenland data

By Laura Faye Tenenbaum

NASA's modified G-III aircraft, with the GLISTIN-A radar instrument visible below, on the runway at Thule Air Base, Greenland.

NASA's modified G-III aircraft, with the GLISTIN-A radar instrument visible below, on the runway at Thule Air Base, Greenland.

"Get to work." The phrase stuck in my head.

I had just walked out of a two-and-a-half-hour debriefing with NASA’s Oceans Melting Greenland (OMG) Principal Investigator Josh Willis, but the whole meeting could be summed up in those three little words of his: Get to work.

It was as though he’d been ringing one of those big ol’ dinner gongs. Data! Hot off the press! Come and get your data! Calling all oceanographers, geologists, paleo-climate scientists: come and get a big ol’ helping of free data.

He made me hungry for data, too.

OMG has just returned from its second spring season. Every April for five years, just before the ice starts to melt, OMG flies a radar instrument over almost every glacier in Greenland that reaches the ocean and collects elevation measurements within a 6.2-mile (10-kilometer)-wide swath for each glacier individually so we can measure how quickly each one is thinning. That’s literally hundreds of glaciers.

“We have more than 70 of these swaths that cover a couple hundred glaciers to create new elevation maps that are high accuracy, high resolution and high quality,” Willis said.

Greenland probe map
The blue squares on this Greenland map show 250 planned locations for probes dropped by plane into ocean waters near the coast. Called Aircraft Expendable Conductivity Temperature and Depth probes, they measure ocean temperature and salinity.

OMG also has bathymetry data from sonar and gravimetry. And we have a year’s worth of Airborne Expendable Conductivity Temperature Depth Probes AXCTD data collected last September plus hundreds of vertical profiles of temperature and salinity taken from ship surveys. “We have temperature measurements in many glacial fjords that have never had a historical temperature profile before. And none of that data is being used to its fullest extent yet.” OMG will set the baseline so we know what the water temperatures are today, and as we look to the future, we can watch them warm. That’s huge. 

I recounted all the times I’ve told someone that many parts of the ocean are still so unknown. I thought about all the times I’ve written about the OMG aircraft flying into remote, uncontrolled airspace, or researching the ocean water-ice interface around Greenland: So many of these places still nameless, still anonymous, still unidentified, still unknown. It’s mind blowing.

And somewhere in all this new data is information about the correlation between the ocean water and the ice as well as the answer to the question of how each glacier may or may not be affected by the waters offshore. “We know that warm water reaches a lot of glaciers. And there have been surveys in few places, but we’ve never had a comprehensive survey of the shelf water before,” Willis said.

OMG is mapping out the edges of glaciers and watching them change year on year on year. The mission measures glacial elevation in the last few kilometers before the glacier hits the water to see exactly how much the glacier shrank or retreated or both. In a few cases, the opposite might happen. Over a single year, a glacier might not have had as much calving or it might have slowed down, which would cause it to thicken and advance.

Aerial shot of a Greenland fjord
Aerial shot of a Greenland fjord shows, at the top, the glacier's origin in the ice sheet, and, at the bottom, its termination point, where it enters a frozen ocean.

There are literally hundreds of glaciers to research and dozens of papers buried in that data. And anybody who wants to can sift through it and publish. “You could get a Ph.D. done really fast,” Willis added enticingly. Here are some recommendations for interesting scientific research:

  • OMG’s temperature data could be used to write oceanography papers about where the warm water is on the shelf and to map out and catalogue which glaciers terminate in deep Atlantic water and which ones sit in shallow water. OMG has enough data to catalogue the depth of the faces of two-thirds of the glaciers around Greenland.
  • Paleo-climatologists and geologists can use new clearly mapped-out OMG bathymetry data to study how ancient glaciers carved troughs in the sea floor. Looking at maps of the seafloor will help us understand the implications for Greenland’s ancient ice sheet. Some flat-bottomed troughs, for example, show evidence of where little ancient rivers must have carved their way through to erode the paleo-glaciers. And sea floor sediments could be analyzed to find out how far the ancient glaciers advanced.
  • Overview papers that compare and contrast the east, west, north and south coasts of Greenland would be incredibly useful to have.
  • Some elevation maps made from historical datasets as well as a few decades’ worth of temperature measurements already exist for some isolated regions across Greenland. Using these historical maps, it’s now possible to compare them with current measurements of temperature and elevation in these locations to observe the changes.
  • OMG is also gathering oceanography data around Greenland. Since the Atlantic Ocean water is very warm and salty and the Arctic Ocean water is cold and fresh, the ratio of those two could be analyzed. Warm Atlantic Ocean water has been in the coastal area around Greenland forever, but how much Atlantic water makes it onto the shelf and reaches the glaciers? This is affected by the bathymetry and the winds, which affect the local currents. And according to Willis, “There’s really still a lot to learn.”

Already there are four downloadable datasets right here! So, come and get it, all you hungry Ph.D. oceanographers.

Get to work.

I can't wait to read your papers,


April 19, 2017, 10:59 PDT

A vast, melting desert

NASA flies northward to monitor Greenland’s glaciers

By Laura Faye Tenenbaum

Scientists strike out for a wall of ice in the far north, where rapidly changing glaciers are being tracked by a project called "Oceans Melting Greenland." Credit: NASA/JPL. View larger image.

Scientists strike out for a wall of ice in the far north, where rapidly changing glaciers are being tracked by a project called "Oceans Melting Greenland." Credit: NASA/JPL. View larger image.

I looked out the window of NASA’s modified G-III aircraft across the expanse. I knew what I would see. I knew it would look like white pillow-y ripples going on and on and on, way farther than anyone could see, like a vast field of white sand dunes stretching away into the distance.

The Oceans Melting Greenland (OMG) aircraft was flying across the entire top half of Greenland from the northwest coast to the northeast coast to make the day’s first science measurements. And the first science flight line was all the way across the Greenland Ice Sheet, across 620 miles (1,000 kilometers) of ice that’s up to 2 miles thick and hundreds of thousands of years old. And although I’d flown in Greenland a bunch of times before, I’d only ever flown over the coastal areas, where glaciers around the ice sheet’s edges carve their way through the Greenland terrain, to cut out deep, narrow fjords over centuries’ time.

Everything here is vast and expansive: the size, the views, the enormous quantity of ice.

Two days before, I’d trekked up to the ice sheet with a few members of the OMG team. We stood in the insanely cold, dry, biting air (Greenland is one of the least humid areas on planet Earth, with the cleanest, clearest air) and gazed into the incomprehensible distance. It was easy to use a snow boot to scrape the 2 inches or so of fine, dry, powdery snow away from the ice sheet to uncover the hard, greenish blue ice.

On the edge of the ice sheet, a slice of ancient ice layers was exposed like a glistening wall, and we’d walked past it on the way up to the top of the sheet. The ice wall was so vertical and so sheer, the snow that hid the other parts of the edge had fallen away, and we could see its smooth surface shining like a gem: striped blue and green. That ice is hundreds of thousands of years old, made from snow that fell year after year after year, eventually becoming compressed and preserved in this cold, dry desert environment. 

Standing on top of the ice sheet, I imagined it under my feet, going down and down and down for a mile or more. 

A mile—or more—of ice.

An exposed wall reveals ice that is hundreds of thousands of years old on the edge of the Greenland ice cap. Credit: NASA/JPL.
An exposed wall reveals ice that is hundreds of thousands of years old on the edge of the Greenland ice cap. Credit: NASA/JPL.

Everything here is vast and expansive: the size, the views, the enormous quantity of ice. Flying over them, the glaciers look like hundreds of broad frozen rivers, each one up to a few miles across, each one channeling its way from the interior of the landmass toward the sea over thousands of years. Each glacier carved out a fjord through the rock and out to sea in the same way a river erodes its channel, except it’s so much bigger, so much slower and the erosional power of the ice is so much more intense. From up here, the glacier’s impossibly slow creep seems frozen in both space and time. But the glaciers are moving. Stress fractures or crevasses, which are easy-to-observe evidence of glacier movement, form as the glaciers slope downhill toward the sea. And of course, we also have scientific measurements. Detailed satellite images show that the terminal edges of many glaciers such as Jakobshavn have receded by as much as 0.4 miles (600 meters) per year in recent times. Scientists also have time-lapse footage of seaward glacier flow.

But having evidence of glacier flow, and even glacier recession, is only part of the story. As a warmer atmosphere and a warmer ocean around the coastline continue to melt the massive amount of ice that covers Greenland, the ice ends up flowing into the ocean, which causes sea level rise worldwide.

A glacier flows toward a frozen fjord on the Greenland coast, as seen from NASA's modified G-III aircraft. Credit: NASA/JPL
A glacier flows toward a frozen fjord on the Greenland coast, as seen from NASA's modified G-III aircraft. Credit: NASA/JPL.
OMG is hoping to gather enough information about the melting glaciers to better predict sea level rise. And that explains why we were here in our NASA G-III on a March morning, flying lines over Greenland’s receding glaciers with our GLISTIN-A Ka-band interferometer radar instrument. “We want the big picture,” said Josh Willis, OMG principal investigator, “and these lines give us data for almost every glacier that reaches the water.  If the ocean is eating away at the edges of the ice sheet, we’ll see it. Bigtime.”

As we flew over, the GLISTIN-A instrument received data from a 12-kilometer swath of whatever is below and off to the sides of it, in this case glaciers. Using these data, we can measure, with great precision, the height of each glacier we fly over. See, when the end of an individual glacier melts and calves into the ocean, the whole glacier speeds up and flows even faster downhill toward the ocean because there’s less friction against the sides and bottom to slow it down. The faster it moves, the more it stretches — like pulled taffy — and when a glacier is all stretched out, its elevation is lower. And because OMG will fly the same science lines along the same coastal glaciers every year for five years in a row, we’ll be able to find out how much elevation each glacier has lost, how fast it’s flowing into the ocean and how much ice has been lost.

NASA's OMG is monitoring the speed of glaciers around Greenland's coastline. Credit: NASA/JPL
NASA's OMG is monitoring the speed of glaciers around Greenland's coastline. Credit: NASA/JPL.
Over my headset, I can hear the pilots discussing the flight path with the instrument engineers. Out the window, I can see Greenland’s northernmost glaciers below us; white upon white upon white.

They sure appear stable, still, enduring. But they’re not. They’re melting.

They sure appear stable, still, enduring. But they’re not. They’re melting.

And northern Greenland, along with the rest of the higher latitudes in the Northern Hemisphere, is experiencing some of the most intense impacts of global climate change right now, today.


Thank you for reading.


Find out more about Oceans Melting Greenland. View and download OMG animations and graphics.

March 16, 2017, 12:10 PDT

Journey through the atmosphere

Guest post by Ellen Gray

Clouds above the Pacific Ocean on the ATom leg from Nadi, Fiji, to Christchurch, New Zealand, on February 6. Credit: Roisin Commane.

Clouds above the Pacific Ocean on the ATom leg from Nadi, Fiji, to Christchurch, New Zealand, on February 6. Credit: Roisin Commane.

The world seems smaller to Steve Wofsy than it used to. He’s the lead scientist for NASA’s Atmospheric Tomography (ATom) mission, an airborne mission to survey the gases on the world’s atmosphere that has just finished up a round-the-world flight.

Atmospheric scientist Steve Wofsy bundled up for the flight from Anchorage, Alaska, to Kona, Hawaii.
Atmospheric scientist Steve Wofsy bundled up for the flight from Anchorage, Alaska, to Kona, Hawaii, on February 1. Credit: Roisin Commane.
I met with Steve in February in Christchurch, New Zealand, at a hotel an easy ten-minute walk from the international airport. The proximity was key because that's where NASA's DC-8 research plane sat amid large warehouse-sized hangars and equipment on a section of the airport run by the U.S. National Science Foundation for research expeditions to Antarctica.

Writer Ellen Gray with NASA’s DC-8 in Christchurch, New Zealand, on February 7.
Writer Ellen Gray with NASA’s DC-8 in Christchurch, New Zealand, on February 7. Credit: Roisin Commane.
Christchurch is at the halfway point of the latest ATom mission, a 28-day near-circumnavigation of the globe. Their journey began Jan. 29 in Palmdale, California, and went north to the Arctic Ocean before zipping down the Pacific Ocean to Hawaii then Fiji on the way to New Zealand. 

NASA’s DC-8, a flying laboratory filled with instruments to measure the atmosphere, in Nadi, Fiji.
NASA’s DC-8, a flying laboratory filled with instruments to measure the atmosphere, in Nadi, Fiji, February 5. Credit: Roisin Commane.
“One day we were in Alaska and the next we were in Hawaii,” he said of the eight-hour research flight that took them from the near darkness of the Arctic winter and snow-covered runways to the belching volcanoes of the Hawaiian Islands where seasons are more of a suggestion of the calendar. When we spoke in New Zealand it was in Southern Hemisphere summer, a breezy 65 F degrees on the coast. Going from the Arctic to the Antarctic and then back again in less than a month, “it really drives home how small our planet is,” he said.

Wofsy is tall and lanky and at 70 is still an active professor and researcher at Harvard University. He began thinking about a mission like ATom 30 years ago to take a slice of the atmosphere from pole to pole to see what gases were there both naturally and from pollution, how they behaved, and how they collectively affected Earth’s climate. Building on years of research and airborne field work, including a mission Wofsy led to sample the air above the Pacific from pole to pole, ATom brings more than 22 instruments and a hundred scientists from universities and agencies around the world to begin to close the loop on some outstanding questions.

Of particular interest are three greenhouse agents: ozone that occurs in the lower atmosphere as a result of human pollution, methane that also primarily comes from human activities, and black carbon, tiny black particles that come from fires that absorb heat and interact with clouds. These three make up the number two, three, and four most important human-emitted greenhouse agents after carbon dioxide, which is also being measured.

"Together they account for almost as much warming of the surface as carbon dioxide," Wofsy explained to me.

What sets them apart is how long they stay in the atmosphere. Unlike carbon dioxide which persists for over a century before being removed from the atmosphere, ozone in the lower atmosphere reacts with other gases within a year and methane sticks around for more than a decade. This means that reducing human emissions of these two gases could make a difference in the greenhouse effect in our lifetimes. But because they're both reactive, their concentration in the atmosphere can vary a lot from place to place. Hence the importance of the up-close, around-the-world measurements made by the instruments on the ATom mission to get a handle on how much is there now and how it may change in the future.

The sky was overcast when we went out to see the plane. NASA’s DC-8 looks like an older-model commercial aircraft from the outside (which it was), but from the inside its all science. Instead of rows of seats, large metal frame structures – racks to hold the instruments and computers – dominate the view with only a pair of seats next to each one. A few scientists were onboard fine-tuning their instruments or resupplying gases and filters.

Instead of hunting for particular gases in particular pollution-prone regions, Wofsy and the science team want to measure everything they can, not just the greenhouse gases — from soot and remnant gases of fires burned on land, sulfur dioxide from volcanoes and coal-burning power plants, and industrial air pollutants. They are flying near some major land masses, but more importantly, they’re flying high over the ocean, the remotest and supposedly cleanest parts of the atmosphere to see how far humanity’s fingerprints on the air have traveled.

The answer: pretty far. This February, above the Arctic, they saw traces of Asian pollution. Above both the Pacific and Atlantic, they saw traces of African fires.

ATom left New Zealand for the southern tip of Chile and then completed the circuit flying north over the middle of the Atlantic Ocean. They arrived back in California at the end of February, finishing their second of four deployments, one to take place in each season. The mission takes to the air next this October.

March 9, 2017, 12:08 PST

What’s the deal with Antarctica and the Arctic?

By Laura Faye Tenenbaum

This beautiful aerial photograph shows a multi-layered lenticular cloud hovering near Mount Discovery in Antarctica, a volcano about 70 kilometers (44 miles) southwest of McMurdo. Credit: Michael Studinger, Operation IceBridge. Download larger image.

This beautiful aerial photograph shows a multi-layered lenticular cloud hovering near Mount Discovery in Antarctica, a volcano about 70 kilometers (44 miles) southwest of McMurdo. Credit: Michael Studinger, Operation IceBridgeDownload larger image.

Most people I meet don’t spend much time thinking about the polar regions on planet Earth; the poles just seem too far away. I mean, Antarctica, really? Only extreme explorers and a few scientists spend time thinking about those frozen places. Most of us live in areas with moderate temperatures, fantasize about tropical vacations and have barely checked out what the far reaches of our planet look like on a map. And even maps neglect the far north and south by stretching them so much that many people have no real idea what the ends of the Earth look like.

I became interested, and then obsessed, with Earth’s icy regions during a particularly hot Los Angeles summer a couple of years ago when I created NASA’s Global Ice Viewer. Sitting in my office scouring NASA vaults for the most intriguing views of our planet’s ice was like going on a wild interstellar journey to someplace beyond my wildest imagination; it changed my view of our planet forever.

These days, I frequently give public speeches and show audiences what the Arctic and Antarctic look like from space. It surprises me how little people know about these portions of our world. Perhaps their biggest misunderstanding is that the Arctic and Antarctic are similar. You know, one’s in the north and the other is in the south; but other than that, they’re the same, right? No, this couldn’t be more wrong. These polar opposites are literally polar opposites.

For starters, the Arctic is an ocean surrounded by land: Eurasia, Greenland, Canada and the United States. It’s only about 5.5 million square miles, which is five times smaller than the Atlantic and 11 times smaller than the Pacific. Antarctica, on the other hand, is a continent surrounded by the entire Southern Ocean.

A graphical representation of the poles.
In 2014, Antarctic sea ice reached a record maximum extent while the Arctic reached a minimum extent in the top ten lowest since satellite records began. One reason we are seeing differences between the Arctic and the Antarctic is due to their different geographies. Credit: NASA's Goddard Space Flight Center.
This may seem like no big deal, but it makes all the difference in the world. It takes a lot of energy to change the water temperature of the entire ocean compared to what it takes to change land temperature, which means Arctic seawater isn’t as cold as the continental ice sheet covering Antarctica. So, the Arctic sea ice (frozen sea water) is about 10 feet thick in winter, whereas the Antarctic ice sheet (compacted freshwater ice) is over a mile thick.

In the winter, the Southern Ocean around the Antarctic continent also becomes covered with sea ice. But every summer most of this sea ice melts. That’s because the ice edge around Antarctica is exposed to open ocean, and every direction you go is north. So, during the summer, most of the sea ice moves north and melts away. This means that very little Antarctic sea ice is more than two years old. But Arctic sea ice is trapped inside the enclosed ocean. This means that during the summer months, even though much of the sea ice melts, it doesn’t melt completely.

More than opposites

Is this complicated enough? If you’ve been reading closely, by now you’ll know that those two types of sea ice are probably super duper different because, yup, you guessed it: The two poles are much more than opposites.

Since 1979, NASA satellite measurements have observed an overall decline in Arctic sea ice due to climate change. Climate change warms the air as well as the ocean water, and melts the sea ice. Climate change has also caused some of the Antarctic ice shelves (which are part of Antarctica’s fresh water ice sheet that extends into the ocean, surrounding the continent) to collapse.

But the story of the sea ice floating around Antarctica in the Southern Ocean is even more complex. This sea ice is not just frozen seawater, like the Arctic sea ice. There’s more snow in the Southern Ocean — that ice is made of sea ice, covered by snow ice (frozen sea water from surface flooding), covered by snow. It’s a snowman ice cream sandwich! And the strong winds down there easily blow this mixture across the ocean surface, making Antarctic sea ice extent highly variable. This year, satellites observed that Antarctic sea ice extent set a record low, dropping to its lowest extent ever recorded.

The fact that our Earth is a crazy complicated place makes it such a challenge to understand, but that same truth also makes it amazing. Earth is never boring, which is why we keep paying attention to and never tire of learning more about it.

Test how much you know and learn more about Earth’s frozen places with these fun quizzes:

As always, I welcome your comments.


This post is an updated version of a previous blog post.

February 23, 2017, 14:23 PST

'H' is for Home, 'P' is for Planet

Guest post by Randal Jackson

"H" is for Home. On, August 30, 2014, the Operational Land Imager on Landsat 8 acquired this image of rivers running through colorful ridges in southwestern Kyrgyzstan.

"H" is for Home. On, August 30, 2014, the Operational Land Imager on Landsat 8 acquired this image of rivers running through colorful ridges in southwestern Kyrgyzstan.

When viewed from space, our planet is wondrous in its diversity, variety and beauty. And as we’ve noted many times in this blog, images of Earth sometimes look like art and often inspire creativity. 

One of our all-time favorite stories about the view of our amazing planet from space comes from one of our sister websites, Earth Observatory. Thank you, Adam Voiland, for this fun piece that depicts all 26 letters of the alphabet from satellite images and astronaut photos. You’ve done a great job of showcasing the vast range of landscapes, topography and geology of planet Earth.

I hope you enjoy this piece as much as we do.

False-color image of the Mackenzie River Delta in Canada.
"P" is for Planet. On August 4, 2005, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor on the Terra satellite captured this false-color image of the Mackenzie River Delta in Canada.

February 16, 2017, 05:00 PST

Science on canvas: Photographs capture thawing Greenland

By Laura Faye Tenenbaum

Credit: Timo Lieber.

Credit: Timo Lieber.

At NASA, I spend a large portion of my work day looking at satellite images of Earth, an amazingly glorious expanded view. Go to our Beautiful Earth, Earth as Art, and Images of Change galleries (the latter is also available as an iPad app) and see for yourself. While you’re checking out our amazing images, you’ll probably also notice something that I see almost every day: Our planet is so beautiful, the images actually look like works of art.

The Earth is our home. And looking at places on the far side of our planet can give you a sense of intimacy with the whole world. That’s how my conversation with aerial photographer Timo Lieber began.

“Photography and science are a quite powerful combination,” Timo Lieber told me. We were discussing his project, THAW, a series of eleven large-scale aerial photographic images that capture the Greenland polar ice cap melting. “The extent of the melting is increasing and the net loss is worsening every single year,” he explained. “I want to put images right in front of people that show that global warming is, in fact, happening.”

“Greenland is a sensational color palette. You rarely find a landscape that’s so pristine as the Arctic.”
- Timo Lieber, photographer

As a photographer, Lieber has wanted to create a body of work that explores in pictures some of the changes that are taking place in the Arctic, to translate the melting ice sheet into beautiful photographs and “to catch the viewers’ attention so that ultimately the viewer gets interested in the subject via the image.”

He teamed up with scientists from Scott Polar Research Institute at the University of Cambridge, who have been conducting research in Greenland for a number of years, and they pointed him in the direction of a series of surface melt lakes that have been increasing in size. Lieber decided to document the lakes in this exhibition of photographs.

Even though Lieber used satellite images to research the location of the lakes, once he was on the ice cap, he found “blue lakes for as far as you can see.” Because the lakes are connected, with one flowing into the other until it drops off into a moulin, he was able to follow one lake to another. “There are lakes and water literally everywhere,” he told me.

A photo from Lieber's 'THAW' exhibition.
Credit: Timo Lieber.
As an aerial photographer, Lieber is always looking for abstract shapes and patterns. “My images need to be visually striking.” Then he added, “Greenland is a sensational color palette. You rarely find a landscape that’s so pristine as the Arctic. You get to work with two dominant colors: blue and white. And I really like the challenge of flying around and finding these patterns that work from a photographic perspective.”

Yes, Greenland is beautiful—the ice, the lakes, the crevasses and the blues that go on and on and on. It’s a true work of art, and according to Lieber, “It’s the perfect canvas for my type of photography.”

Thank you for reading.


February 1, 2017, 03:00 PST

Glaciers on the edge

By Laura Faye Tenenbaum

Credit: NASA's Oceans Melting Greenland mission

Credit: NASA's Oceans Melting Greenland mission

“This year we’re gonna bring it!” Oceans Melting Greenland (OMG) Principal Investigator Josh Willis told me excitedly. “It’s the beginning of year two of this five-year airborne mission, which means that by comparing data from the first and second years, we’ll be able to observe changes in Greenland’s glaciers and coastal ocean water for the first time.” Glaciers around Greenland’s jagged coastline have been melting into the ocean and causing increased sea level rise, so measuring the amount of ice mass loss will help us understand the impact of these changes, Willis said. “Will we see 5 feet of sea level rise this century … or more?”

See, Earth’s ocean, more than the atmosphere, is responsible for creating a stable climate. And as global warming has increased the temperature of the ocean waters surrounding Greenland, that warmer ocean water is melting the ice sheet from around its edges. “Hey! The ocean is eating away at the ice sheet!” Willis often cries when explaining the mission. And Team OMG is measuring how much of that warm water could be increasing due to climate change.

Decoding the environment

I understand how Willis and Project Manager Steve Dinardo get excited about measuring sea level rise. Greenland’s ice melt is accelerating, which explains why NASA is paying attention to it. Plus, after a successful first year, the team is fully aware of the stark beauty of Greenland’s rugged landscape and seascape and the rewards of bonding as a team. Dinardo told me he was “ecstatic about the incredible progress Team OMG has made in the last twenty-two months.”

After a successful first year, the team is fully aware of the stark beauty of Greenland’s rugged landscape and seascape and the rewards of bonding as a team.
As scientists, decoding the natural world is our way of caring about the environment. We care about Greenland’s icy coastline, so we go there. We go there and observe. We go there and measure. For there is something undeniable about the sheer beauty of this planet, and any time you get to experience it is a moment to feel exuberant and alive. Plus, flying around with a great team in a modified NASA G-III aircraft ain’t too shabby either.

But wait. Before I continue, there’s something you probably noticed: Willis said he named this Greenland observing expedition Oceans Melting Greenland, or OMG for short, because, hey, OMG is the exact response you might have when you find out what’s going on up there.

Parts of Greenland’s coastline are so remote, so difficult to access by boat, that they’d remain uncharted, especially under areas that are seasonally covered with ice. Imagine the edge of an unimaginably complicated winding coastline, that unknown place where ice meets water meets seafloor. Big chunks of remnant sea ice clog up the water, and the glacier has retreated so recently that the coastline is changing as fast as, or even faster than, we can study it.

The seawater around 400 meters deep is 3 to 4 degrees Celsius warmer than the water floating near the sea surface. And the sea floor bathymetry influences how much of that warm subsurface layer can reach far up into the fjords and melt the glaciers. So, to learn about the interface between where the bottom of the ice sheet reaches out over the seawater and down into the ocean, OMG began by mapping undersea canyons on the M/V Cape Race, a ship equipped with an echo sounder, which sailed right up the narrow fjords on the continental shelf surrounding Greenland to the places where the warmer Atlantic Ocean water meets the bottoms of the frozen, 0-degree glaciers. The crew had to snake in between floating icebergs and weave in and out of narrow fjords. The Cape Race used a multibeam echo sounder to map undersea canyons, where the warm seawater comes in contact with and melts the glaciers.

The next four years

In the spring of 2016, the Oceans Melting Greenland (OMG) team began surveying glacier elevation near the end of marine-terminating glaciers by precisely measuring the edges of the ice sheet on a glacier-by-glacier basis, using the Airborne Glacier and Land Ice Surface Topography Interferometer (GLISTIN-A), a radar instrument attached to the bottom of a modified NASA G-III aircraft. Data collected this spring and over the next four years can be compared with data collected in the spring of 2016 so we can determine how fast the glaciers are melting.

As scientists, decoding the natural world is our way of caring about the environment.
The investigation continued into last fall, with the team dropping more than 200 Aircraft eXpendable Conductivity Temperature Depth (AXCTD) probes that measured ocean temperature and salinity around Greenland, from the sea surface to the sea floor, through a hole in the bottom of the plane. “In most of these places,” Willis told me, “there’s been no temperature and salinity data collected. Ever.”

The team will drop more ocean probes across the same locations to find out “how much ice melts when the water is this warm,” what the melt rate is, and how much that rate is increasing, because no one knows the melt rate yet. 

No one.

Big picture project

“OMG is a big picture project,” Willis explained. ”We want to see what’s happening in the ocean on the large scale and what’s happening to the ice sheet on the largest scales.”

As part of Team OMG, I also flew on NASA’s G-III into uncontrolled airspace to places where no other aircraft had flown before, into narrow and steep ice-covered fjords, winding in and out, up and down, over and through to observe and measure, like scientists do. I saw the brilliant white ice carve its way through steep brown valleys into open ocean water. I saw the glorious expanse of white upon deep blue going on and on and on below us as we flew just 5,000 feet above the winding coastline. It was extraordinary.

And if you just thought “OMG,” Willis would be proud.

Thanks for reading.