June 2016 InFORMal Update

InFORM results from our coastal monitoring network Oct 2014 – Mar 2016.

Coastal monitoring: Results from 34 samples, collected in December – March, did not find any of the Fukushima fingerprint isotope, 134Cs (2 year half-life), in coastal waters. Low levels of 137Cs (~30 year half-life) were present in all of the samples. These new data continue to lie along the increasing trend which indicates that the leading edge of the Fukushima plume is in BC’s coastal waters.

Monthly averaged 137Cs data from the BC coast collected by the InFORM citizen science network between October 2014 and March 2016. The dashed linear trendline shows that levels of 137Cs have been increasing over this period. Error bars indicate one standard deviation. Large error bars in Februray and May 2015 were months when Ucluelet samples tested positive for 134Cs. Colors are the same as used in the spatial map of the data.

The above trend is clear and shows a steady rise that would predict that the average sample will have double the initial background concentrations of 137Cs by this coming summer. While still far below the 10,000 Bq m-3 level of concern for cesium radionuclides in drinking water, these more contaminated samples should also more regularly contain the Fukushima fingerprint isotope, 134Cs.

While the increasing 137Cs trend is clear for the whole coast, it is also evident that each region is telling the story of how ocean waters circulate in coastal British Columbia.

Analysis as above, but with data grouped into regions as follows:  Haida Gwaii / North Coast: Lax Kw’alaams, Prince Rupert, Masset, Hartley Bay, Sandspit, North Van Is / Central Coast: Bella Bella, Port Hardy, Winter Harbour, West Coast Van Is: Tofino, Ucluelet, Bamfield, Strait of Georgia: Powell River, Vancouver, Salt Spring Island, South Van Is: Port Renfrew, Victoria.

Looking at this regional graph and focusing on the period from August 2015 – February 2016, we see the highest concentrations of 137Cs shift from appearing on the west coast of Vancouver Island northward to Haida Gwaii. (Note: Since the results from March 2016 are incomplete with more samples to be run, I will not interpret findings for that period.) This northward shift of the highest concentrations may indicate that the bifurcation of the North Pacific Current (NPC), the current transporting Fukushima contamination, shifted northward during that period.

Cartoon of the North Pacific Current (NPC) and it’s bifurcation region on the North American coast based on Argo float data from Freeland (2006) and Cummins and Freeland (2007). Ocean station Papa and stations along Line P are visited three times a year as part of the InFORM oceanic monitoring program. Figure by J Kellogg.

As you can see in the figure, the NPC splits into the California Current and the Alaska Current when it hits North America. The exact location of this bifurcation may vary widely from southeast Alaska to central Oregon depending on the prevailing winds. Regardless of where the bifurcation occurs, the Alaska Current receives ~60% of the water from the NPC with the rest heading south along the coast in the California Current. If the bifurcation shifted northward during the last 6 months of 2015, the core of the Fukushima plume would have been pushed with it to the north as well resulting in the increasing values from Haida Gwaii. This may mean that samples from more southerly stations will increase at a slower rate. Validation of this proposed shift in the current bifurcation will require further investigation into satellite data which proved unavailable prior to publication.

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