Sea Shorts: How Iceland's Jökulsárlón lagoon is changing the coast

Stretching out of the mountains on Iceland’s southern coast, the Breiðamerkurjökull glacier is a sight to behold. Around 100 years ago, as temperatures warmed, the glacier began to retreat. The glacier left behind a lagoon which has continued to grow as the glacier continues to shrink. Jökulsárlón lagoon is definitely cold, but its waters are also calm. It’s also a temporary home to a plethora of icebergs, sheered off from Breiðamerkurjökull.

Some of Jökulsárlón lagoon’s icebergs take on a rich blue colour (apart from that almost crystal-clear one right in the middle!). Credit: Samantha Andrews/Ocean Oculus.

Some of Jökulsárlón lagoon’s icebergs take on a rich blue colour (apart from that almost crystal-clear one right in the middle!). Credit: Samantha Andrews/Ocean Oculus.

Eventually, the icebergs make their way out of the lagoon through a 100-meter wide and 20-meter deep channel into the ocean. Some will live out the rest of their days floating in the sea, but for others, life stops at the beach adjacent to the mouth of the channel. Here they create what is akin to a gallery of natural artworks along the black sand.

Whilst the Breiðamerkurjökull glacier is busy donating these ‘ice diamonds’ to the coast, there is something important for the beach that is not - sediment.

Iceland’s Diamond Beach is like an art gallery filled with beautiful creations. Credit: Samantha Andrews/Ocean Oculus.

Iceland’s Diamond Beach is like an art gallery filled with beautiful creations. Credit: Samantha Andrews/Ocean Oculus.

When glaciers form they carve up the landscape, taking with them debris like rocks, stones, pebbles, gravel, and soil. As the glacier retreats, this debris is left behind, often in rivers created by the melting ice. In the case of Breiðamerkurjökull, much of this sediment ended up on on either side of the mouth of the channel linking Jökulsárlón to the sea - what is now Diamond Beach. As more sediment accumulated, the beach grew.

When Jökulsárlón lagoon began forming in the early 1930s, much of Breiðamerkurjökull’s sediment became trapped in the lagoon instead. The result? According to a study* by Dr Helgi Björnsson (University of Iceland) back in 1996, “comparison of maps from 1904 and 1989 shows that the coastline has retreated over a distance of 4 km on both sides of the river outlet”. That’s right - either side of the channel’s mouth, the beaches are getting smaller! Since the Breiðamerkurjökull glacier is still retreating*, we can expect the beaches to also continue to retreat.

*No paywalled science - this is an open access link!

The Sea Shorts series offers tiny glimpses into all things ocean and coastal. Read more Sea Shorts and other stories here.