By: Dianna Parker
Our partners in the Pacific Northwest have noticed an increase in marine debris on shorelines this past month, including small vessels that likely washed out to sea during the tsunami in Japan in 2011. Four boats arrived in Washington over the Memorial Day weekend alone. The flurry of activity may seem unusual and sudden, coming after a relatively long stretch where we still saw some debris — but not this much. So what’s the deal? Why are we getting a spike now?
Here’s what Amy MacFadyen, oceanographer and modeler in the Office of Response and Restoration’s Emergency Response Division, has to say about possible reasons for the increase:
This seasonal arrival of marine debris—ranging from small boats and fishing floats to household cleaner bottles and sports balls—on West Coast shores seems to be lasting longer into the spring than last year. As a result, coastal managers dealing with the large volume of debris on their beaches are wondering if the end is in sight.
Beachcombers know the best time to find treasure on the Pacific Northwest coast is often after winter storms. Winter in this region is characterized by frequent rainfall (hence, Seattle’s rainy reputation) and winds blowing up the coast from the south or southwest. These winds push water onshore and cause what oceanographers call “downwelling”—a time of lower growth and reproduction for marine life because offshore ocean waters with fewer nutrients are brought towards the coast. These conditions are also good for bringing marine debris from out in the ocean onto the beach, as was the case for this giant Japanese dock that came ashore in December 2012.
So, to recap: Winter winds push nutrient-depleted water onshore and bring debris with it. As Pacific Northwest residents may recall, there were a series of big winter storms in February and March.
Amy goes on to describe a period known as the “spring transition” that can occur anytime between March and June, where a change in winds ushers nearshore surface water back offshore. Then, nutrient-rich water moves in (we call this “upwelling”). The timing of this transition period may also affect the volume of marine debris reaching Pacific Northwest beaches. The later the transition, the more time the debris pushed toward shore from winter storms has to reach shore.
According to researchers, we’re in that transition period now, which means the end to the spike is near:
Interestingly, the model shows many fewer particles came ashore in the spring of 2013 than in the other two years. This may be related to the timing of the spring transition. According to researchers at Oregon State University, the transition to summer’s upwelling conditions occurred approximately one month earlier in 2013 (early April).
The good news for coastal managers—and those of us who enjoy clean beaches—is that according to this indicator, we are finally transitioning from one of the soggiest springs on record into the upwelling season. This should soon bring a drop in the volume of marine debris on our beaches, hopefully along with some sunny skies to get out there and enjoy our beautiful Pacific Northwest coast.