Beaten to the punch, part 2: Tsunami Debris

Back in early 2012 Jim Brennan and I published a short technical report through Washington Sea Grant focused on assessing likely debris accumulation scenarios for Washington State associated with "tsunami debris" from the March 2011 Tohoku tsunami.  The report was a response to some dire messages that were promulgated at the time through the media, and even by some ocean circulation experts.  There was some very real anxiety about the impacts to Washington's coast from this load of debris.

Anyway, we used some analysis of previous research and observations, coupled with some liberal hand-waving, to estimate what we considered a likely range of debris loading to Washington's beaches in the first four years after the tsunami, and we came up with an estimate of 1-14 times the background debris loading level.

So that was great, and we got some limited but very nice feedback on the report from some coastal managers on the west coast, and found that it was making its way into management decisions as far afield as B.C.  As the years passed, though, I found myself with a desire to revisit our suggested likely scenario, and compare it to what really happened.  I was involved in a few tiny efforts in the subsequent years, but largely I could never pull it off.  Thankfully, someone else did.  

Earlier this year Cathryn Murray published a paper with Nikolai Maximenko and Sherry Lippiatt examining whether there was a detectable tsunami signal in temporal patterns of marine debris on the west coast, based on monitoring data.  The short answer...there was!  And they used data collect in the Olympic Coast National Marine Sanctuary to estimate that the tsunami debris contributed to a roughly 10-fold increase in debris load to beaches in Washington State...which sits squarely within our 2012 likely estimate.  Very cool!

Fig. 1. Mean yearly debris influx of indicator items from 2003 to 2015 at sites in northern Washington State, USA. Letters denote significantly different groups using Tukeys HSD posthoc comparisons).  From Murray et al., 2018.  

The figure above shows the estimated average rates of loading of a subset of indicator debris items tracked in monitoring efforts over 10+ years at sites in the Olympic Coast National Marine Sanctuary.  This is the source of the estimate that the Tohoku tsunami led to a ~10x increase in debris load.

There is quite a bit more ground covered in this paper, some of it interesting relative to what we assessed back in 2012, and some of it just cool new territory (i.e. the documentation of seasonal spikes in debris loading, which I blogged about back in 2014 in the thick of the tsunami debris period).  Really cool to see this work, and really useful for assessing when and where debris is likely to come ashore in the future associated with any input of debris in the Pacific Ocean.