How did rising sea level help form fjords in Alaska and Norway?

Fjords in regions like Alaska and Norway were formed through a combination of intense glacial erosion and subsequent changes in sea level. During periods of glaciation, massive glaciers carved deep, U-shaped valleys into the landscape, often eroding the bedrock far below the existing sea level.12

As these glaciers melted following the end of glacial stages, the global sea level rose. This rising water inundated the deep, glacially carved troughs, transforming them into the narrow, steep-walled marine inlets known as fjords. Because these valleys were originally deepened by ice, the resulting fjords are often exceptionally deep, sometimes featuring a shallower rock threshold or sill at their mouth where the glacier's erosive power was less intense. This process of marine inundation effectively "drowned" the glacial valleys, creating the modern fjord estuaries observed today.1324