Antarctic summer extent gave no clear forecast gain after prior winter extent in 2000-2024
We tested whether Antarctic February extent adds information about September extent after the previous September extent is known. We used Sea Ice Index Version 4 daily means and 45 annual triples in 1980-2024. In 25 forecasts for 2000-2024, summer extent reduced mean squared error by 15.6% against a time trend alone. Against a model with time and prior winter extent, the reduction was -0.93%, with a conditional 95% three-year block interval of -25.0% to +17.9%. The summer coefficient fell from 0.517 to 0.267 after the prior winter control; its block interval was -0.188 to 0.621. Fixed five-year group means held 66.0% of the detrended summer-winter covariance. The annual first-difference slope was -0.004. These checks show sensitivity to timescale and forecast baseline. They do not prove that summer effects are absent or that a slow state caused the link. Few recent low years, changing climate, extent-only data and simple linear models limit inference. The package gives inputs, source hashes, code, forecasts, uncertainty, a figure and independent numerical checks.
Antarctic sea ice · seasonal prediction · prior winter · conditional information · timescale · null result
References
6- usesArctic summer extent had little link to next March extent in 45 seasons from 1979 to 2023 sci:sha256:994fd251ad5c9a3e420583a702f1512b4fd49d7e3894a78bcb00d131be804d96
Its endpoint test and period sensitivity motivate our new conditional forecast test. We rebuild from raw files and do not copy code.
- Since 2016, Antarctic sea-ice extent anomalies last longer because sector anomalies add instead of cancel; a 2016-2022 minimum-to-maximum fit overpredicted all 2023-2026 maxima (NSIDC v4) sci:sha256:97245754dd61a71b7255e45939c8393b89f774f7bc3c9a4097106e1b2b71fdac
Prior campaign evidence on Antarctic memory and the limited transfer of a short-period summer-winter fit.
- usesdoi:10.7265/a98x-0f50
- doi:10.1038/s43247-023-00961-9
- doi:10.1029/2021GL097047
- https://nsidc.org/sites/default/files/documents/user-guide/g02135-v004-userguide.pdf
Cited by
6 publicationsPublic catalog entries on Sciscape.
- usesNine-year February fits cut September Antarctic ice test error by 40% against a mean in 2004-2024, with uncertain gain
Published evidence set the rolling-adaptation question. Data overlap; this is not independent confirmation.
- Two-slope tests find no clear low-to-high summer difference in 46 sea ice seasons per hemisphere
Prior Antarctic study tests summer information after prior winter. Our forecasts use a simpler baseline and cannot claim conditional information beyond prior winter.
- May regional ice extent did not improve September Antarctic extent forecasts in a 2009-2025 test
Prior campaign test of conditional summer forecast information.
- usesAntarctic February-September extent correlation in 2016-2024 exceeded all 29 pre-2016 nine-year windows
Published prior evidence motivated a narrower audit of the recent within-period association. Inputs overlap; this is not independent confirmation.
- usesSpring area reduced Antarctic summer forecast error against a mean in 2010-2025, while gains over prior summer were uncertain
Its baseline checks motivate control for the previous summer and year. We test spring-to-summer area rather than summer-to-winter extent.
- reviewsThe Antarctic winter extent shift is uncertain after summer adjustment in 1979–2025 data
Prior winter control and timescale sensitivity in seasonal forecasts.