Friday, April 21, 2023

Sea level rise came first for the Vikings, now it's coming for you

 From PNAS:

[Viking occupation of Greenland] coincided with a transition from the Medieval Warm Period to the Little Ice Age and Southern Greenland Ice Sheet advance. We demonstrate using geophysical modeling that this advance would have (counterintuitively) driven local sea-level rise of ~3 m (when combined with a long-term regional trend) and inundation of 204 km2. This largely overlooked process led to the abandonment of some sites and pervasive flooding. Progressive sea-level rise impacted the entire settlement and may have acted in tandem with social and environmental factors to drive Viking abandonment of Greenland.

My fairly obvious contribution to the discussion is that 204 square km isn't that big of a loss relative to the total non-glaciated land nearby and the relatively small number of 2000 people and their livestock on all that land. 

 

 (Flooded areas in light blue.)

OTOH, the study refers to the loss being "fertile lowland," which is likely correct - areas with the least elevation differential to sea level will have the least erosion and highest accumulation of soil and organic matter. To the extent the settlers could actually grow crops and not just pasture, this would have been an especially important loss. The paper doesn't mention this, but it also looks like the flooding could have made it much harder to move from place to place on land. People could move in boats I suppose, but moving livestock that way wouldn't be easy, and boats were likely in short supply as they ran low on wood and iron, and apparently never acquired techniques to make sealskin kayaks from the Thule (pre-Inuit) culture.

As the paper says, sea level rise is a contributing influence, not the only thing causing the Viking collapse. We'll see how much better we can do better in modern times.

Finally as an aside, it's interesting to think about how the gravitational mass of ice can attract the sea to itself, something that rises and falls over time like lunar and solar tides (although not as predictably). Seems to me it could be thought of as an "ice tide" that moves at the rhythm of the climate cycles.