Regional variability in sea-level rise is complex. To understand sea-level change means understanding not only the transfer of land ice into the ocean, but also, for example, how the gravitational field of Earth changes as massive water volumes shift around the planet. As the ice sheets diminish under climate change, so too do their gravitational fields. In the process, previously held ocean water is released to migrate elsewhere on Earth. Sea level actually falls in the vicinity of diminishing glaciers and ice sheets, not only due to the weakening of local gravity, but also the rapid removal of ice mass enhances rebound of the Earth’s crust out of the ocean.
In Scandinavia, sea-level changes measured by satellite since 1993 vary from no change at Reykavik, Iceland to about 150% of the rate of global average sea-level rise at Helsinki, Finland. It is perhaps counterintuitive to think that simply because Iceland is closer to the diminishing Greenland ice sheet that its sea-level change is extremely different from more distant Finland. But when it comes to the gravitational redistribution of ocean mass, it is the ice masses farthest away from a location that influence its sea-level rise the most. Looking towards the future, Scandinavian cities will similarly not experience identical sea-level changes. Take Oslo and Copenhagen as an example. Remarkably, only 600 km separates these cities but the year 2100 sea-level change projected at Copenhagen is about 300% of that at Oslo.
Understanding the origin of sea-level rise, especially the contribution from Arctic land-ice, as well as the regional variability in sea-level rise, particularly within the Baltic Sea, are therefore core themes of ongoing sea-level research at GEUS.