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作者:綜合 来源:焦點 浏览: 【大中小】 发布时间:2024-11-10 01:43:21 评论数:
The Arctic is warming faster than any other region on the planet, driving sea ice to record lows and threatening iconic species from polar bears to walruses and harp seals.
Demonstrating the increased precariousness of America's Earth observing satellite capabilities, the malfunctioning of a single sensor on a Defense Department spacecraft is forcing scientists at the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado, to scramble to put a backup system in place.
The outage has prevented the NSIDC from posting sea ice extent data since March 31.
SEE ALSO:Freakishly mild Arctic winter leads to lowest winter sea ice cover on recordThe troubles concern a sensor on the Defense Meteorological Satellite Program (DMSP) F17 satellite, which went into orbit in 2006, with an expected lifespan of at least 10 years.
IceBridge sea ice scientist Nathan Kurtz stands in front of an ice wall of the Store Landgletscher, also known as Great Land Glacier, near Camp Tuto at Thule, Greenland.Credit: NASA/Michael StudingerThe instrument, technically known as the 37 Gigahertz vertical polarization channel, is an important part of the algorithm that allows scientists to measure sea ice extent.
In the words of NSIDC director Mark Serreze, the sensor "went wacky" in early April.
Aware that the F17 satellite was getting old, the NSIDC had been running calibration tests to maintain a consistent record of sea ice extent between the sensor on the F17 satellite and the DMSP F19 satellite, which was launched in 2014.
But that ended on Feb. 11, 2016, when F19 went completely dark.
"Well, F19 died,” Serreze said. “That was not good, we kind of picked the wrong horse there.”
The important thing for Serreze and his colleagues is that any breaks in sea ice data are minimized, which is why they take time to iron out any kinks from one instrument before they switch to it. Such calibration periods, as they're known, are a crucial part of climate science research and monitoring.
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Because of the F17 sensor outage, though, they are being forced to cope with a discontinuity or gap in the data.
"The problem was initially seen in data for April 5 and all data since then are unreliable, so we have chosen to remove all of April from NSIDC’s archive," the organization stated on its website.
To restart the gathering of sea ice extent information, scientists are running parallel data streams from instruments on two other Defense Department satellites, known as DMSP F16 and F18. Both of these satellites have a design lifetime that ends this year, though many spacecraft continue functioning long after that point.
Serreze said the hope is that sea ice data from these satellites will be available within the next week or so, just in time for the start of the annual summer melt season.
Running out of backups
Once the F16 and F18 satellite stop functioning, though, it's unclear what the NSIDC will rely upon to keep gathering intelligence on sea ice extent in near real-time. It's possible that new satellites going into service in the next few years, such as NASA's IceSat-2, will take up this mission.
Another hope is for the last in the series of Defense Department meteorological satellites, known as DMSP F20.
This satellite has been built, however it never launched due to a lack of funds.
"The real concern is that we need that long, consistent climate record and we are definitely at risk of losing that."
This means that if either of the F16 or F18 satellite's fail, sea ice extent data, which is a key marker of climate change and vital information for ship captains of cruise liners and cargo vessels traversing newly accessible Arctic waters, may again be compromised, but this time for a far longer period.
“It’s not like we’re completely blind,” Serreze told Mashablein an interview, since information from a new Japanese satellite is helping to fill in some gaps regarding ice extent.
However that data, which is from an instrument known as the Advanced Microwave Scanning Radiometer, or AMSR, is not the same exact information as what comes from the Defense Department satellites, which compromises the long-term record.
Satellites have been observing Arctic sea ice since 1979. During that time, sea ice extent in March, when the ice pack typically hits its maximum annual value, has declined at a rate of 2.7 percent per decade, according to NSIDC. A steeper decline has been seen in September sea ice extent, when the annual minimum tends to occur.
Climate scientists rely on long and consistent records of climate indicators, such as sea ice extent and temperatures. The satellite woes put such consistent records into jeopardy, Serreze said.
Artist illustration of a DMSP satellite.Credit: Defense department“If you’re interested in climate you’re interested in long, consistent records, and that’s really where my concern rises from is having that long view of satellites," he said in an interview.
"The real concern is that we need that long, consistent climate record and we are definitely at risk of losing that."
The satellite troubles come at a crucial time for the Arctic climate. Sea ice extent hit a record low annual maximum in March after a freakishly mild winter in much of the Arctic. That warmth has continued since then, weakening sea ice further.
“The story that we’ve been seeing for most of this year is much the same,” Serreze said.
The satellite concerns are shared by other scientists at the National Oceanic and Atmospheric Administration (NOAA), who are facing a potential yearlong gap in polar satellite data that is vital for maintaining the accuracy of weather forecast models.