Greenland sea levels do not always move in the same direction as the global ocean, according to new research from the Geological Survey of Denmark and Greenland (GEUS) based on sediment cores from the Isortoq Fjord in southern Greenland. The study, published in Quaternary Science Reviews, found that when the Greenland Ice Sheet lost mass after the last Ice Age, the land rebounded and the local relative sea level fell, even while global sea level was rising.
What the Isortoq study found about sea-level change
The research offers what GEUS describes as its most detailed reconstruction so far of sea-level change in southern Greenland over roughly the past 10,000 years. By analysing sediment cores taken from lakes and submerged basins in the inner Isortoq Fjord, researchers traced when those basins were cut off from the sea and when they were flooded again.
The result is a more complex picture than the one often associated with climate change. On a global scale, melting land ice adds water to the oceans and pushes sea levels higher. But close to a shrinking ice sheet, the opposite can happen locally. As the ice loses weight, the Earth’s crust rises and the reduced gravitational pull of the ice mass means less ocean water is held nearby.
According to the study, relative sea level in the area fell rapidly during the Early Holocene, dropping from around 36 metres above present mean sea level to close to today’s level by about 9,000 years ago. During the Middle Holocene, when temperatures were warmer and the Greenland Ice Sheet was smaller, local relative sea level may have been more than 20 metres below today’s level.
Why relative sea level matters in Greenland
The key concept in the paper is relative sea level, meaning the sea level measured locally in relation to the land surface. This is different from absolute or global sea level, which tracks the average amount of water in the world’s oceans.
In Greenland, these two trends can move in opposite directions. As ice retreats, the land can rise faster than the sea rises locally. That does not cancel the broader climate signal. It shows instead that the impact of ice melt is geographically uneven and that regions close to the melting ice can behave very differently from tropical or lower-latitude coasts.
Lead author Gregor Luetzenburg of GEUS said the most striking finding was the scale of the changes and their local variation, suggesting that sea-level responses near the Greenland Ice Sheet are more dynamic than previously assumed.
Climate models may be missing part of the picture
The study also compared the new field data from Isortoq with existing models of glacial isostatic adjustment, the process through which the Earth’s crust responds to the loading and unloading of ice. Here too, researchers found a mismatch.
According to the paper, the observed changes in southern Greenland were larger than those predicted by both one-dimensional and three-dimensional models. That matters because these models are used to reconstruct past ice-sheet behaviour and to improve projections of future sea-level change.
If current models underestimate how quickly and how strongly local sea level responds to ice loss, they may also understate the regional effects of future warming. That does not mean global sea-level rise is slower than expected. It means local responses around former and present ice sheets may be more variable, and in some places more extreme, than standard modelling suggests.
Why Greenland ice loss affects other coasts differently
The findings also reinforce a broader point in climate science: where ice melts matters. When Greenland loses ice, the redistributed meltwater does not affect every coastline equally. Researchers noted that tropical regions can experience a larger share of sea-level rise linked to Greenland’s melt than areas close to Greenland itself.
The reverse logic applies to Antarctica. For northern European coastlines, including Denmark, Antarctic melt can have a disproportionately strong impact on sea-level rise compared with an equivalent amount of ice loss from Greenland.
This makes Greenland an important natural laboratory not only for Arctic research, but also for understanding how future climate change could reshape coastal risk far beyond the North Atlantic.
A more dynamic Arctic coastline than expected
Taken together, the Isortoq findings point to a landscape in constant motion, shaped by the interaction between ice loss, land uplift and ocean redistribution. The study does not challenge the fact that climate change is raising sea levels globally. Instead, it refines the picture by showing that local sea-level trends near major ice sheets can look very different from the global average.
For Greenland, that is a reminder that climate change does not produce uniform outcomes even within the same system. For the Nordic region and Europe, it is also a warning that better local data from the Arctic are essential if scientists want more reliable forecasts of future coastal change.
