Alaska Landslide Inventory

Back in November a study was published that looked at historical news reports to create a new inventory of landslides in Alaska dating back to 1883.  Many other inventories have been produced over the years for specific purposes, but this approach focuses on the human exposure to landslides.

https://link.springer.com/article/10.1007/s10346-025-02663-z

As one would expect from increased population and better reporting, the number of reported landslides has increased tremendously over time, although the number of landslide-caused fatalities has not increased (largely because of the 1936 Juneau landslide).   The authors argue that a major part of the increase in landslide numbers is related to warming of the climate, which is hypothesized to cause a higher frequency of freeze-thaw events, rain-on-snow events, and rainfall extremes.

Extreme rainfall events in mid-high latitude areas are often produced by "atmospheric rivers", and there's a lot of interest among climate scientists in historical and future trends in these events.  To cite one example, the following study indicates that mid-latitude atmospheric rivers have become more frequent in Northern Hemisphere winter (as defined by moisture transport in the ERA5 reanalysis data).

https://www.nature.com/articles/s41612-025-01191-w

The following figure from the paper (click to enlarge) shows a region of increased frequency in the Gulf of Alaska, adjacent to landslide-prone Southeast Alaska.

Extreme precipitation events have increased widely across southern and southeastern Alaska, according to this data:

Just for fun, I pulled out the ERA5 precipitation amounts for each landslide identified by Darrow and Jacobs as having been triggered by excessive rain.  The chart below shows the rain excess above normal for the 7 days ending on the landslide date, at the ERA5 grid cell closest to the landslide location.

Of course, ERA5 is thoroughly incapable of reproducing local rainfall variations in complex terrain, which is no doubt a critical factor in many cases, so this analysis is very crude.  Nevertheless, it's mildly interesting that the fraction of events with a rain excess above +4 inches more than doubled from pre-1990 (10%) to post-1990 (22%).

One other comment - the increase in atmospheric river events near southern Alaska in recent decades is related to a greater frequency and persistence of La Niña-like (and negative PDO-like) anomalies in the Pacific, with increased warming in the tropical West Pacific:

https://www.science.org/doi/epdf/10.1126/sciadv.adq0604