[HN Gopher] Antarctic sea ice hits lowest winter maximum on reco...
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Antarctic sea ice hits lowest winter maximum on record: US data
Author : wglb
Score : 60 points
Date : 2023-09-27 19:57 UTC (3 hours ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| [deleted]
| rq1 wrote:
| inf sup is a decreasing function.
|
| Cheers!
| greenyoda wrote:
| Recent discussions:
|
| https://news.ycombinator.com/item?id=37542499
|
| https://news.ycombinator.com/item?id=37540768
|
| https://news.ycombinator.com/item?id=37530218
| 1970-01-01 wrote:
| This chart tells it better: https://berkeleyearth.org/wp-
| content/uploads/2023/09/arctic-...
| anonporridge wrote:
| This one is best, and is interactive and regularly updated.
| https://nsidc.org/arcticseaicenews/charctic-interactive-sea-...
| myshpa wrote:
| Also here: https://climatereanalyzer.org/clim/seaice/ (click
| Switch Hemisphere)
| anonymousiam wrote:
| Unless I am mistaken, 16.96 million square kilometers is more
| than 15.9 million square kilometers (the recorded antarctic sea
| ice coverage in August 1966).
|
| https://ntrs.nasa.gov/api/citations/20140017193/downloads/20...
| anonporridge wrote:
| From the article.
|
| > "This is the lowest sea ice maximum in the 1979 to 2023 sea
| ice record by a wide margin," said the NSIDC, a government-
| supported program at the University of Colorado at Boulder.
| feerceKitteh wrote:
| The paper linked is also only an estimate using a different
| source of data.
|
| >"Even adding in the Nimbus V single-channel Electrically
| Scanning Microwave Radiometer (ESMR) data extends the record
| by only another 6 years and that data is not as com- plete or
| consistent [2]."
|
| > "This paper presents Antarctic sea ice estimates for winter
| 1964 and 1966 derived from early Nimbus satellite data as an
| initial step towards creating Earth Science Data Records of
| sea ice in the 1960s."
| anonymousiam wrote:
| "The paper linked is also only an estimate using a
| different source of data."
|
| Yes, an estimate with an error margin of +-0.3 million
| square kilometers. Also, the 1979-2023 data is from
| multiple "different" sources.
| mikestew wrote:
| A brief skim of the paper also suggests that the data are
| from different means of measurement. In the case of
| measurements from the 60s, those came from infrared and
| visible light, whereas from the 70s on its passive microwave.
| The paper is proposing a method to use the old data as
| passive microwave, and thereby extending the sea ice record.
|
| So is OP's comparison still valid? (Assuming I'm not
| completely off base here.)
| Karellen wrote:
| From your link, in the introduction:
|
| > Sea ice extent data from multi-channel [1979-2012] passive
| microwave sensors provided one of the longest-running climate
| records from satellites in the form of the sea ice extent index
| [1]. However, while the more than 30-year record is now long
| enough for typical climate-scale change, it is still relatively
| short. Even adding in the Nimbus V single-channel Electrically
| Scanning Microwave Radiometer (ESMR) data extends the record by
| only another 6 years and that data is not as complete or
| consistent [2]. _Earlier data are only available from
| operational ice charts that are of variable quality and do not
| cover all ice-covered regions. This was particularly true in
| the Antarctic, where there were few ice charts before 1972._
|
| Sections _IV. ERROR ANALYSIS_ and _V. ANTARCTIC SEA ICE EXTENT
| ESTIMATES, 1964 VS. 1966_ then go on to explain how calculating
| ice extents before the passive microwave sensor era is
| unreliable, with gems like:
|
| > The 1964 satellite data provide fairly complete coverage over
| the Antarctic, allowing the ice edge to be clearly seen in most
| areas in at least one image over the three weeks. This provides
| a reasonably robust estimate of sea ice extent for the period,
| though some uncertainty results from the variation of the ice
| edge location during the time period. The Nimbus I data had at
| most eight images of any area in the three weeks of data
| collection, so _it was difficult to distinguish homogeneous
| clouds and homogeneous ice_.
|
| > Coverage of Nimbus II AVCS images for the Antarctic for 1966
| was fairly complete but the film record ends on August 31 so a
| direct comparison with the 1964 estimate from Nimbus I is not
| possible. [...] The results for May 1966 had higher uncertainty
| because images often lacked clean ice edges. For both May and
| June there were longitudes with no ice edge detection, leading
| to further uncertainty
|
| > The fact that our August 1966 is such an outlier indicates
| potential issues in the Nimbus August data. In addition, the
| drop in extent from July to August is not seen in the passive
| microwave record and _is not physically likely_.
|
| > Unfortunately, we have been able to uncover any corroborating
| information on Antarctic sea ice in 1964 or 1966, including any
| data or imagery from US Navy aircraft over-flights.
|
| Basically, any measurements from before 1979, and especially
| before 1972, are not particularly reliable. Some researchers
| have produced the best numbers they could from the data they
| did have, but there needs to be a big asterisk by them.
| beowulfey wrote:
| That number is estimated using very different methodologies,
| it's hard to compare to the modern numbers!
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(page generated 2023-09-27 23:01 UTC)