Jet Propulsion Laboratory, Pasadena, Calif.
There are two primary causes of global mean sea level rise – added water from melting ice sheets and glaciers, and the expansion of sea water as it warms. The melting of Antarctica’s ice sheet is currently responsible for 20-25 percent of global sea level rise.
But how much of a role will it play hundreds of years in the future?
Ahead of tomorrow’s press teleconference on climate change and global warming, NASA just released its 2018 statistics on temperature readings worldwide.
Earth’s global surface temperatures were the fourth warmest since 1880, according to independent analyses by NASA and the National Oceanic and Atmospheric Administration (NOAA).
Media Advisory: M19-003
NASA, NOAA to Announce 2018 Global Temperatures, Climate Conditions
Climate experts from NASA and the National Oceanic and Atmospheric Administration (NOAA) will provide the annual release of global temperatures data and discuss the most important climate trends of 2018 during a media teleconference at 11:30 a.m. EST Wednesday, Feb. 6.
Data from NASA’s Aura spacecraft, illustrated here, were analyzed by scientists to produce improved estimates of sulfur dioxide sources and concentrations worldwide between 2005 and 2014.
- “Understanding Sea Level,” a summary of decades of scientific research that has shaped our knowledge of sea level rise: its causes, including a warming, expanding ocean and melting ice on land; projections of future sea level rise; and ways in which humanity might adapt, largely drawn from NASA data.
- An interactive data analysis tool, launching in mid-2016, that will allow direct access to NASA datasets on sea level. Users will be able to manipulate these datasets to automatically generate charts, graphs and maps of sea surface height, temperature and other factors. The analysis tool will also allow users to make forecasts of future conditions, as well as “hindcasts” — retroactive calculations of past trends and conditions.
- News highlights and feature stories with strong visual elements that explore the findings of sea level researchers in detail.
- An extensive library of published papers on sea level-related topics, hyperlinked to individual citations throughout “Understanding Sea Level.”
- A multimedia section with dynamic still and video imagery, and a glossary of sea level terms.
- A “frequently asked questions” section maintained by sea level scientists. Users can submit questions to scientists and data managers.
A new NASA study of ocean temperature measurements shows that in recent years, extra heat from greenhouse gases has been trapped in the waters of the Pacific and Indian oceans. Researchers say this shifting pattern of ocean heat accounts for the slowdown in the global surface temperature trend observed during the past decade.
Researchers Veronica Nieves, Josh Willis and Bill Patzert of NASA’s Jet Propulsion Laboratory, Pasadena, California, found a specific layer of the Indian and Pacific oceans between 300 and 1,000 feet (100 and 300 meters) below the surface has been accumulating more heat than previously recognized. They also found the movement of warm water has affected surface temperatures. The results were published Thursday in the journal Science.
During the 20th century, as greenhouse gas concentrations increased and trapped more heat energy on Earth, global surface temperatures also increased. However, in the 21st century, this pattern seemed to change temporarily.
“Greenhouse gases continued to trap extra heat, but for about 10 years starting in the early 2000s, global average surface temperature stopped climbing and even cooled a bit,” said Willis.
In the study, researchers analyzed direct ocean temperature measurements, including observations from a global network of about 3,500 ocean temperature probes known as the Argo array. These measurements show temperatures below the surface have been increasing.
The Pacific Ocean is the primary source of the subsurface warm water found in the study, though some of that water now has been pushed to the Indian Ocean. Since 2003, unusually strong trade winds and other climatic features have been piling up warm water in the upper 1,000 feet of the western Pacific, pinning it against Asia and Australia.
“The western Pacific got so warm that some of the warm water is leaking into the Indian Ocean through the Indonesian archipelago,” said Nieves, the lead author of the study.
The movement of the warm Pacific water westward pulled heat away from the surface waters of the central and eastern Pacific, which resulted in unusually cool surface temperatures during the last decade. Because the air temperature over the ocean is closely related to the ocean temperature, this provides a plausible explanation for the global cooling trend in surface temperature.
Cooler surface temperatures also are related to a long-lived climatic pattern called the Pacific Decadal Oscillation, which moves in a 20- to 30-year cycle. It has been in a cool phase during the entire time surface temperatures showed cooling, bringing cooler-than-normal water to the eastern Pacific and warmer water to the western side. There currently are signs the pattern may be changing to the opposite phase, with observations showing warmer-than-usual water in the eastern Pacific.
“Given the fact the Pacific Decadal Oscillation seems to be shifting to a warm phase, ocean heating in the Pacific will definitely drive a major surge in global surface warming,” Nieves said.
Previous attempts to explain the global surface temperature cooling trend have relied more heavily on climate model results or a combination of modeling and observations, which may be better at simulating long-term impacts over many decades and centuries. This study relied on observations, which are better for showing shorter-term changes over 10 to 20 years. In shorter time spans, natural variations such as the recent slowdown in global surface temperature trends can have larger regional impacts on climate than human-caused warming.
Pauses of a decade or more in Earth’s average surface temperature warming have happened before in modern times, with one occurring between the mid-1940s and late 1970s.
“In the long term, there is robust evidence of unabated global warming,” Nieves said.
NASA uses the vantage point of space to increase our understanding of our home planet, improve lives and safeguard our future. NASA develops new ways to observe and study Earth’s interconnected natural systems with long-term data records. The agency freely shares this unique knowledge and works with institutions around the world to gain new insights into how our planet is changing.
For more information about NASA’s Earth science activities, visit: http://www.nasa.gov/earth
Those who feel as though they’ve been living in the never-ending winter of the movie “Frozen” this year may be glad to hear that the spring thaw is now typically arriving up to two weeks earlier in the Northern Hemisphere than it did 20 to 30 years ago. But the changing date of the spring thaw has consequences far beyond reducing the number of mornings when you have to scrape off your windshield.
One ecosystem where scientists would most like to understand the effects of changing freeze/thaw cycles is boreal forests, the great ring of green covering the land nearest the North Pole. The forests of Alaska, Canada, Scandinavia and Siberia cover almost 15 percent of Earth’s land surface. The Arctic is warming more quickly than lower latitudes, and the way these forests respond to this rapid change could provide valuable clues about our planet’s warmer future.
But we know very little about how the boreal forests are changing. Millions of square miles have no roads or even villages. “What we have now are very sparse, seasonal measurements from the ground,” said John Kimball, a professor of systems ecology at the University of Montana, Missoula, and a member of the science team for NASA’s Soil Moisture Active Passive (SMAP) mission, launched Jan. 31. “We do have long-term, global satellite data sets that are sensitive to freeze-thaw, but they tend to be very coarse.” That means each measurement averages the status of a large area. Like a mosaic made of large tiles, these data cannot show much detail.
That’s about to change. By the end of April, SMAP will begin monitoring the frozen or thawed state of the landscape north of 45 degrees north latitude (about the latitude of Minneapolis) every two days. The primary mission of SMAP is to measure the amount of moisture in the top few inches of soil globally, but it also detects whether that moisture is frozen or in liquid form. SMAP’s radar measurements, with “tiles” only half a mile to a mile and a half (1 to 3 kilometers) across, will reveal far more detail than scientists now have about the freeze/thaw status of the land surface.
Why is greater detail needed? In the Arctic, the timing of the spring thaw can vary considerably within a small area. Because the returning sun is low on the horizon, the shadowed north side of a hill may remain icy many days after plants have started growing again on the sunlit south side. Those early spring weeks are critical in the short Arctic growing season. “Once the vegetation thaws, boom! Photosynthesis takes off,” Kimball explained. “You can get your highest rates of photosynthesis within a few weeks after the thaw, and a later thaw can mean much lower vegetation growth for the season. We need observations at what I call the landscape level to more precisely monitor those patterns and changes.”
During photosynthesis, plants absorb carbon dioxide from the air. The carbon stays in their wood, roots and leaves, and when they die, most of it remains in the soil. That makes undisturbed forests what scientists call carbon sinks — places that remove carbon from the atmosphere. Longer unfrozen seasons in the Arctic give forests more time to grow and spread, increasing the extent of the carbon sink.
On the other hand, climate warming has increased the occurrence of droughts and wildfires in the Arctic. A burning forest spews enormous amounts of carbon into the atmosphere; in scientific terms, it is a carbon source. Thus, global climate change is causing the northern forests both to absorb and to release more carbon.
With so little Arctic data to crunch, models of Arctic land processes do not agree on which of these trends is prevailing, much less what the future could hold. Lack of consensus does not indicate fundamental disagreements on the physical processes involved, according to JPL scientist Josh Fisher, a member of the SMAP algorithm team. The problem is that, at present, if you put the Arctic’s emitted carbon on one side of a scale and absorbed carbon on the other, the scales would almost balance. “The source/sink balance is usually close to zero, and it’s very easy to get on the wrong side of the zero,” he said. Yet the wrong answer on this fundamental question can cascade into a chain of wrong answers in the course of a model simulation. SMAP’s fine-scale observations have the potential to improve modelers’ understanding of both today’s situation and how it may change in the future.
This spring, SMAP will spin up in time to track the spring thaw in the boreal forest with the detail scientists need — as Princess Anna in “Frozen” says, “For the first time in forever.”
For more about SMAP, visit:
JPL is managed for NASA by the California Institute of Technology in Pasadena.
Researchers at the University of Texas at Austin, NASA and other research organizations have discovered two seafloor troughs that could allow warm ocean water to reach the base of Totten Glacier, East Antarctica’s largest and most rapidly thinning glacier. The discovery likely explains the glacier’s extreme thinning and raises concern about its impact on sea level rise.
The result, published in the journal Nature Geoscience today, March 16, has global implications because the ice flowing through Totten Glacier alone is equivalent to the entire volume of the more widely studied West Antarctic Ice Sheet. If Totten Glacier were to collapse completely, global sea levels would rise by at least 11 feet (3.3 meters). As in the West Antarctic Ice Sheet, complete collapse of Totten Glacier may take centuries, although the timing of retreat in both places is the subject of intensive research.
East Antarctica has appeared to be stable compared with the rapidly melting western side of the continent. The new finding shows that “Totten Glacier and the East Antarctic Ice Sheet are a much more interesting and dynamic part of the sea level rise story than we’d previously thought,” said co-author Dustin Schroeder, a scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California. Schroeder helped analyze data from an ice-penetrating radar to demonstrate that ocean water could access the glacier through the newfound troughs.
In some areas of the ocean surrounding Antarctica, warm water can be found below cooler water because it is saltier, and therefore heavier, than the shallower water. Seafloor valleys that connect this deep warm water to the coast can especially compromise glaciers, but this process had previously been seen only under the West Antarctic Ice Sheet. Deep warm water had been observed seaward of Totten Glacier, but there was no evidence that it could compromise coastal ice.
The newly discovered troughs are deep enough to give the deep warm water access to the huge cavity under the glacier. The deeper of the two troughs extends from the ocean to the underside of Totten Glacier in an area not previously known to be floating.
The data for this study were gathered as part of the International Collaboration for Exploration of the
Cryosphere through Airborne Profiling (ICECAP) project, which, together with the East Antarctic component of NASA’s Operation IceBridge mission, made the first comprehensive survey of the Totten Glacier Ice Shelf and nearby regions between 2008 and 2012. Other coauthors of the study come from research organizations and universities in Australia, France and England.
For more information on the new study, see:
To learn more about Operation IceBridge and ICECAP, visit:
The paper is available at: