Polar Explorer

Web Mercator is infinite at 85.05°. That is a property of the projection, not a limit of the data — ICON has values right up to the pole — and it means no Mercator raster can contain a pole at any size. The global Explorer stops at 85° because that is as far as the projection goes.

So the caps get a polar stereographic render instead: true at 70°, oriented on Greenwich, and guaranteed to 45° on every meridian — the corners reach further still, to about 29°. A stereographic raster cannot be draped on a Mercator map surface, which is why this page is a small purpose-built map rather than another layer on the Explorer.

It matters here because the two places Mercator fails hardest are the two where a hemisphere behaves as one system: the polar vortex, the sea-ice margin, and the cross-pole flow between Siberia and Canada are all things a map cut at 85° simply cannot draw. A stretched vortex over Scandinavia is a German forecast three weeks out, and this is the only projection that shows it whole.

Only the global run is here, and that is the data rather than a gap. ICON-EU stops at 70.5°N and has no southern half at all, so a stereographic render of the nest would be a disc of nodata with a crescent of Lapland on one edge. ICON global has values to 90° in both hemispheres, which is what a cap needs.