Cooperative Institute for Research in Environmental Sciences

New CU Boulder-led paper could improve understanding of Greenland’s contribution to sea-level rise


In northwestern Greenland, glaciers flow from the main ice sheet to the ocean in see-sawing seasonal patterns. The ice generally flows faster in the summer than in winter, and the ends of glaciers, jutting out into the ocean, also advance and retreat with the seasons.

Now, a new analysis shows some important connections between these seasonal patterns, sea ice cover and longer-term trends. Glaciologists hope the findings, accepted for publication in the June edition of the Journal of Geophysical Research-Earth Surface and available online now, will help them better anticipate how a warming Greenland will contribute to sea level rise.

“Rising sea level can be hard on coastal communities, with higher storm surges, greater flooding and saltwater encroachment on freshwater,” said lead author Twila Moon, a researcher at the National Snow and Ice Data Center (NSIDC). NSIDC is part of the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder. “We know that sea level will go up in the future,” Moon said. “The challenge is to understand how quickly it will rise, and one element of that is better understanding how Greenland glaciers behave.”

Moon and colleagues from the University of Washington focused on 16 glaciers in northwest Greenland,using imagery from the German Space Agency's TerraSAR-X satellite and NASA's Landsat 7 and 8 satelltes to collect detailed information on glacier speed, terminus position (the “end” of the glacier in the ocean) and sea ice conditions, during the years 2009-2014.

Sea ice had an important influence on the glaciers: When the waters in front of the glacier were completely covered by sea ice, the ends of the glaciers often advanced out away from land; icebergs that might otherwise have broken off and floated away stayed attached. When sea ice broke up in the spring, the ends of the glaciers usually quickly retreated back toward land as icebergs broke away.

By contrast, seasonal swings in glacier speed had little to do with sea ice conditions or glacier terminus location. Rather, the speed (velocity) of ice flow is likely responding to changes in the surface melt on top of the ice sheet and the movement of meltwater through and under the ice sheet.

Over the longer-term, however, Moon and her colleagues found a tight relationship between the speed of glaciers and terminus location. When sea ice levels were especially low and glaciers’ toes (termini) retreated more than normal and then didn’t re-advance, the glaciers sped up, moving ice toward the sea more quickly. While low sea ice is likely not the full cause of the changes, it may be a visible indication of other processes, such as subsurface ice melt, that also affect terminus retreat, Moon said.

It’s important to recognize that the mechanisms driving seasonal glacier changes—in northwestern Greenland and around the world—are not necessarily the same ones driving longer-term trends, Moon said. Knowing the differences may help researchers better anticipate the impact of anomalously low sea ice years, for example.

“We do know we’re going to see sea ice reduction in this area, and it’s possible we can begin to estimate how that may affect glacier velocities,” Moon said. It’s also possible, she said, that researchers and communities interested in long-term glacial changes—the kind that affect sea levels—may not need to focus as much on seasonal advance and retreat of the rivers of ice.

“It may be that we need to instead pay more attention to these out-of-bounds events, these anomalous years of very low sea ice or very high melt that likely have the greatest influence on longer-term trends.”

This research was funded by NASA and the National Science Foundation. 

NSIDC is part of CIRES, which is a partnership of NOAA and CU Boulder.

High-resolution images available for download on CIRES’ Flickr account, News Release album


This is a joint release of the Cooperative Institute for Research in Environmental Sciences (CIRES), the University of Colorado Boulder, and the American Geophysical Union (AGU).

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Ice experts from the University of Colorado Boulder, the U.S. Navy, the U.S. National Ice Center and other institutions have developed a straightforward new technique for estimating sea ice concentration in the Arctic Ocean, and the new method improves the U.S. Navy’s sea ice forecast by almost 40 percent. With shipping on the rise in the Arctic Ocean, improving these short term forecasts makes navigating in Arctic waters safer.

The Navy, the National Oceanographic and Atmospheric Administration (NOAA) and others have been seeking to improve sea ice forecasts, said Pamela Posey of the U.S. Naval Research Laboratory in Mississippi. In the remote Arctic, unanticipated sea ice can slow science research vessels and create problems for Navy submarines.

“It’s especially important to have accurate forecasts given rapidly changing conditions in the Arctic,” Posey said.

The new system—which captures current sea-ice conditions more accurately and in greater detail by blending several streams of data—has been used operationally in Navy forecasting since February, Posey said. Florence Fetterer with the National Snow and Ice Data Center (NSIDC) and colleagues developed the blended input approach, and NRL has now shown it improves 6-hour  forecast accuracy by 40 percent year-round. During the summer, forecasts improved even more than that, they reported in a paper in The Cryosphere, a journal of the European Geosciences Union.

NSIDC is part of the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder, a partnership of CU Boulder and NOAA.

The new ingredients now going into the Navy’s official sea ice forecasts are satellite data and human interpretation of sea ice presence or absence from satellite sources, said Pablo Clemente-Colón, Chief Scientist of the U.S. National Ice Center (NIC), a collaboration of the Navy, NOAA and the U.S. Coast Guard. “This is one of the first times that human analysis is ingested operationally into a major forecast model,” he said.

A couple years ago, Posey and others recognized that sea ice forecast models—used by Navy submarines, the U.S. Coast Guard and many others just as they use weather forecasts—had improved, with more detailed or “higher resolution” output.  But just as with weather forecasts, these models have to start with accurate initial conditions, and observations of sea ice had not kept pace with models. The Naval Research Laboratory asked experts at NSIDC to see what could be done.

“Our idea was pretty simple, to combine two types of measurements,” said Fetterer, a CIRES scientist who is NSIDC’s NOAA liaison. With colleagues from NASA, the NIC and the Naval Research Laboratory, Fetterer blended data from the high-resolution satellite-based Advanced Microwave Scanning Radiometer 2 (AMSR2) with MASIE (“may-zee,” the Multisensor Analyzed Sea Ice Extent), itself a blended product that includes human interpretation of many satellite imagery sources as well as other information. The MASIE product often catches ice that the microwave data alone miss, especially in summer, when melt ponds on the surface of the ice appear as ocean to the sensor. Where there is ice, the AMSR product supplies an estimate of ice concentration that the forecast model needs.

The resulting high-resolution dataset can capture even small patches of sea ice a few miles across, which are easy to miss in some satellite datasets. That means better input into forecasts, and more accurate output, too. “We expect this combined product is going to do a much, much, much better job at initializing the Navy’s forecast model,” Fetterer said.

“It is really helping us, and it’s providing a better product for the whole community that uses and depends on accurate sea ice information from forecast modelers to anybody with assets in the Arctic,” Clemente-Colón said.

CIRES is a partnership of NOAA and CU Boulder.


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A tougher federal standard for ozone pollution, under consideration to improve public health, would ramp up the importance of scientific measurements and models, according to a new commentary published in the June 5 edition of Science by researchers at NOAA and its cooperative institute at the University of Colorado Boulder. 

The commentary, led by Owen Cooper of the Cooperative Institute for Research in Environmental Sciences and NOAA’s Earth System Research Laboratory, looks at how a new, stricter ozone standard would pose challenges for air quality managers at state and local levels. Last November, the Environmental Protection Agency proposed lowering the primary ozone standard from 75 parts per billion (ppb) to 70 or 65 ppb, based on ozone’s known effects on children, the elderly, and people who have lung diseases such as asthma. A decision by the EPA Administrator is expected in October 2015. 

NOAA researcher Andy Langford checks out data on ozone levels as an instrumented NOAA Twin Otter aircraft flies over the Los Angeles Basin during 2010. Langford is co-author of a commentary published in Science that looks at how a new, stricter ozone standard—under consideration to improve public health—would boost the need for more ozone measurements and analysis. 
Credit: Richard Marchbanks/CIRES and NOAA

The problem for state and local officials is that ozone pollution has several sources, some of which are beyond their borders. At any given place, a certain amount of the ozone pollution comes from local emissions by vehicles and other sources. Additional amounts can blow in from pollution sources across the ocean or in other parts of the United States. And some ozone is produced from natural sources or descends from the upper atmosphere’s ozone layer.

Sorting all this out is where science comes in, says Cooper. “It’s not easy, but we do know how to figure out where the ozone comes from. This source information is exactly what air quality managers will need to know when the margin for allowable locally produced ozone shrinks.”

Ozonsonde release

Ozone is a pollutant that has respiratory health effects in humans and also impairs plant growth and damages crops. It is produced when emissions of nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight. Controls on NOx and VOC emissions from vehicles, power plants, and other sources have enabled many U.S. counties to meet the 75 ppb standard, but the number of counties in “nonattainment” status (currently at 227) would jump to 358 or 558 if the standard is revised to 70 or 65 ppb, respectively.

The new commentary suggests that to quantify how much ozone flows into the United States from all upwind sources, additional measurements would be needed, from instruments on the ground, on balloons, and on aircraft. These observations could help scientists and air quality managers evaluate the performance of the computer models that are used to determine sources of ozone at a particular location. Once the models can successfully replicate the observed ozone levels, scientists and air quality managers will have greater confidence in the model estimates of how much of that observed ozone is beyond the reach of domestic control measures. 

That information is critical because the U.S. regulatory framework has procedures for exceptions and other allowances if non-local factors are significant for a given locality. And, those outside factors have been growing in recent decades, with sources in South and East Asia pushing up the baseline of ozone that enters the western U.S., for example.

U.S. ozone-monitoring sites. Dark blue dots show sites that did not comply with the health-based federal standard of 75 parts per billion (ppbv) between 2011 and 2013. Additional sites would have been out of compliance with a 70 ppbv standard (light blue), 
a 65 ppbv standard (red), and a 60 ppbv standard (orange). A new commentary published in Science by CIRES and NOAA authors looks at how a new, stricter ozone standard—under consideration to improve public health—would boost the need for more ozone measurements and analysis. 
Credit: Cooper et al., Science 
 

“The ozone baseline is rising, especially in high-elevation regions of the western U.S. that are more strongly influenced by high ozone coming from upwind sources or from the stratosphere. Lowering the federal ozone standard to protect public health will reduce the wiggle room for air quality managers. We point out that measurements and science will be crucial to successfully navigating the new regulatory landscape,” Cooper said.

The EPA has stated that in their upcoming regulations and guidance, they will assist states in ensuring that sources of ozone that are outside of U.S. borders do not create unnecessary control obligations.

CIRES is a partnership of NOAA and CU Boulder.

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