Arguments
Graphics for Sea Ice Minimum 2011
Posted on 6 October 2011 by Peter Hogarth
Arctic Ice: The Canary in the Coal Mine? A brief introduction
Arctic ice extent and volume over the satellite record since 1979.
Whilst some have argued at various points over the past few years that sea ice is recovering after the dramatic 2007 Summer sea ice losses, the reality is that both extent and overall volume are on an increasingly downwards multi-decadal trend, as older ice is lost and what little perennial ice that remains is thinning. Data from NSIDC (National Snow and Ice Data Centre)and PIOMAS (Pan-Arctic Ice-Ocean Modeling and Assimilation System). Uncertainties in NSIDC SSMI ice extent are around +/- 50 x 103 km2 whilst conservative estimate of uncertainties in PIOMAS volume are +/- 1.35 x 103 km3.
The Summer 2011 sea ice extent minimum was very close to, or had even dropped below (depending on which sensor and processing method is used) the 2007 record value. The minimum levels for the past five years are the lowest five in the record to date. The annual average Arctic extent value is also tracking very close to the previous minimum value in 2007, and may yet drop further this year. The 2011 Arctic ice volume (both the Summer minimum and annual average), are estimated to be at record low levels, the average volume having dropped by 45% over the past 33 years. Accounting for the uncertainty levels, there is currently less Arctic sea ice than at any time in the records, and the scientific consensus is that this downwards trend will continue for the foreseeable future.
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