PenguinTracker / Glaciers / Shirase Glacier

Shirase Glacier

Outlet glacier · no detectable change · measured 2013–2022

Shirase Glacier is showing no detectable change in speed. Speed across 518 km² of grounded ice averaged 923 m/yr in 2022 — 2.5 metres a day — measured from satellite feature tracking over 9 usable years.

Measured speed by year (blue). The dashed line is the least-squares fit across every usable year — not significant at twice its standard error. Years whose coverage of the measured pixel set fell below 90% are dropped rather than interpolated, because feature tracking succeeds preferentially on fast crevassed ice and a sparse year is biased fast.

Grounded ice (solid) against its floating shelf (dashed), both indexed to 100 in 2013. Grounded -0.7% ± 2.8 · Shelf +3.9% ± 8.4, quoted as ±2 standard errors of the fitted slope. Neither moves further than its own uncertainty, so neither change is one we can claim. Both series are refit here over the 9 years the two domains share, so the comparison is like for like; the flat figures above are each measured over that domain's own longer window. Every glacier compared this way →

Measured domaingrounded ice

Measured trunk518 km²

Years used9 of 23 in the archive

Period2013 – 2022

Speed in 2013944 m/yr

Speed in 2022923 m/yr

Floating shelf, same years+2.8% across 446 km²

Fitted change-0.7%

Fitted trend-0.7 m/yr² ± 1.5

Significancenot significant — slope is 0.5× its standard error

Mean coverage100% of the measured pixel set

Position70°06'S 38°54'E

What this number is, and is not

This is the speed of the ice surface, averaged over a fixed set of trunk pixels that carry valid data in every year reported. It is measured on grounded ice only. Grounded ice and floating shelf are separated using the masks the ITS_LIVE files carry, because they mean different things: grounded ice speeding up puts more ice across the grounding line, while a shelf that is already afloat displaces no extra water however fast it moves — and shelf speed jumps after a calving. Here the shelf changed +2.8% over the same years. The fitted change is quoted rather than the endpoint change (-2.2%), because an endpoint figure rides on two single noisy years.

Coverage before 1999 is negligible and no continent-wide acceleration figure is defensible from this product. Per-glacier series are only reported where the coverage gate is met. Each box is a fixed window around the trunk, not a drainage basin, so these are speeds over a measured area and not mass-balance figures.