Sea-level in Greenland was surprisingly dynamic after the last Ice Age

Published 20-01-2026
News

New research provides the most detailed picture to date of how the sea-level has changed in southern Greenland since the last Ice Age, documenting falling sea levels coupled to ice melt. This raises new questions about how well we understand the interaction between ice, land, and sea in a warming climate.

Overview map of Isortoq Fjord. Green and orange points in Panel C show the specific lakes investigated and dotted lines show the past extent of the Greenland Ice Sheet following deglaciation after the last Ice Age. (Maps: GEUS)

How does sea-level respond when the climate warms and icesheets disappear? Instinctively, one would think that the sea-level rises as more water is added from melting ice sheets to the ocean. While this is true for global scale sea-level, the opposite can be the case at local scale in the areas close to retreating or disappearing ice sheets.  

This conundrum is at the heart of a new study that reconstructs sea-level changes in southern Greenland over the past ~10,000 years. The results reveal rapid sea-level fall after deglaciation and suggest much lower relative sea-levels during a time in the past when it was warmer than it is today. Moreover, the study indicates that commonly used climate models may underestimate how dynamic the response of local sea-level change is to a warming climate.

The study is based on analyses of sediment cores from lakes and submerged basins in the inner part of Isortoq Fjord in southern Greenland. The sediment layers act as a geological archive, recording when basins were isolated from the sea – and later inundated again.

“The sediments give us a uniquely detailed insight into how the landscape responded as the ice retreated. They provide a rare opportunity to reconstruct past sea levels with a high degree of precision,” says Gregor Luetzenburg, postdoctoral researcher at the Geological Survey of Denmark and Greenland (GEUS) and lead author of the study.

Sediment cores from the lakes (Photo: GEUS)

A landscape reshaped after the last Ice Age

When the last Ice Age ended around 11,700 years ago and the climate warmed, the world entered the geological epoch called the Holocene in which we are living today. This led to the retreat of vast ice masses in Greenland, triggering a tightly coupled response between ice loss, land uplift, and sea-level change in both directions.

The study identifies three distinct phases in this development based on the sediment samples from the Isortoq Fjord:

  • Early Holocene – falling relative sea-level 

    Rising temperatures led to the continued retreat and thinning of the Greenland Ice Sheet from its maximum extent during the last Ice Age. As the weight of the ice on the Earth’s crust began to decrease, crustal rebound led to local uplift in Greenland, causing the sea to retreat locally relative to the land. Over just a few thousand years, the coastline in Isortoq Fjord retreated from its highest level to approximately the level we know today.

  • Middle Holocene – lowest relative sea level

    Temperatures reached its maximum during the Middle-Holocene, the Greenland Ice Sheet were at its minimum extent and local relative sea level was significantly lower than today – by up to ~20 metres.

  • Late Holocene – rising relative sea-levels

    The pattern shifted again. Temperatures became cooler, the ice sheet regrew and crustal uplift was reversed in Greenland. Crustal reloading led to relative sea level gradually rising again in Greenland, returning to approximately present-day levels within the last millennium.

Together, the results paint a picture of a landscape in constant motion. As ice melts away, the land surface rises – and this can cause local sea level to fall, even in a world where global sea level is rising.

Challenges existing models

When the researchers compare their observations from Isortoq Fjord with existing models of glacial isostatic adjustment (GIA) – which describe how the Earth’s crust responds to ice loading and unloading and how this affects relative sea level – a clear mismatch emerges. The observed changes are larger than those predicted by the models.

“Our results show that current models underestimate both how fast and how strongly the relative sea-level responds when ice melts. If models fail to reproduce past changes correctly, we also risk misjudging future sea-level change – which highlights the need for better data and more refined models,” says Gregor Luetzenburg.

This insight is not only of historical interest. More accurate models are essential if data from Greenland are to be used to improve projections of future sea-level change in a rapidly warming climate.

Absolute (eustatic) sea-level change

Refers to changes in the global mean sea level – in other words, how much water there is in the world’s oceans overall. It is mainly driven by climate change through land-ice melt and thermal expansion of seawater.

Relative sea-level change

Describes how sea level changes locally relative to the land surface. In Greenland and Denmark, the land can move up- or downwards in response to changes in the weight of the overlaying ice mass when the ice sheet retreats, causing relative sea level to fall locally – even while global sea level is rising.

Gregor Luetzenburg
Postdoc
Glaciology and Climate
Phone+45 50101193
Johanne Uhrenholt Kusnitzoff
Editor
Press and Communication
Phone+45 91333954

Scientific publication

The study is published in Quaternary Science Reviews and is available here:

https://doi.org/10.1016/j.quascirev.2025.109787