Deep Waters In British Columbia Mainland Fjords Show Rapid Warming And Deoxygenation From 1951 To 2020

Many complex fjord systems cross British Columbia's coastline. A 70 year (1951-2020) time series analysis of temperature, salinity, and oxygen in four such fjords between similar to 54 and 50(o)N (Douglas Channel, Rivers Inlet, Knight Inlet and Bute Inlet) shows that changes were greatest in deep waters between the sill and the bottom. In Rivers, Knight and Bute Inlet, the deep water temperature increased by 1.2-1.3 degrees C over 70 years, up to two times the global average for open ocean waters at corresponding depths, while salinity increased by 0.1-0.2, and oxygen decreased by 0.4-0.7 mLL(-1). The most northern inlet, Douglas Channel, showed a temperature increase of 0.8 degrees C from 1951 to 2016, while trends in oxygen and salinity were not statistically significant. An analysis of Apparent Oxygen Utilization suggests that the deep waters in Douglas Channel are more readily exchanged with the outer coast than the three other fjords.