Deep water temperatures in fjords along BC’s Central Coast have increased 1.2–1.3°C over the past 70 years, a recent report shows.
Big changes for the ocean
“These are big changes for the ocean. They are changes that can shift ecosystems and impact species. Oolichan, for example, don’t like being in waters that are warmer than 8°C and in some of the inlets we don’t see waters that are colder than 8°C anymore,” said Jennifer Jackson of the Hakai Institute, lead author of a study of Rivers, Knight and Bute Inlets, as well as the Douglas Channel.
Loss of oxygen
“The loss of oxygen trend that we are seeing in the coastal waters is really large, it is about 20% in deep water over the past 70 years. It will often put these deep waters into a realm where there is not enough oxygen for most animals to survive. It can shrink their habitat,” explained Jackson.
“In the 1950s, 60’s and 70’s there was always enough oxygen throughout Bute Inlet, or Knight Inlet or Rivers Inlet, but during the last ten years there are sometimes months at a time when there isn’t enough oxygen below, say, 300 metres.”
Sea Stars, zooplankton, most fish species, prawns and crabs are among the species affected by this change.
Some of the study’s data comes from Bute Inlet, UBC collected data in Bute from the1950s to 1980s and DFO collected sparse data there from the 1990s to 2014
“Hakai started sampling Bute Inlet in 2017. We’ve been collecting monthly data since then. So we were able to resolve the seasonal cycle and also put this data into perspective for a longer time series. It is really unique … there aren’t many coastal areas in the world that have such a long time series,” said Jackson.
They also studied Rivers Inlet, Knight Inlet and the Douglas Channel.
“They all showed a consistent trend, the only one that was a little bit different was the Douglas Channel,” she explained.
This was partially because they only had data until 2016, and also because the Douglas Channel was regularly flushed by the ocean. The waters in Rivers, Knight and Bute Inlets are more stagnant.
As the waters in all four bodies are warming, this is happening in deep water inlets throughout the coast.
The world’s oceans are also warming (0.08°C a year), but a little less than half as the inlets (0.2°C a year).
What is making the Inlets warm faster?
“We know the waters from about 150 metres offshore, in the open ocean, are the source of the deep water in these inlets. They are transported to the deep water once a year by upwelling. The Northwesterly winds push off the surface water, from the coast, and they are replaced by deep water that upwells onto the shelf and it eventually goes down into the fjords,” said Jackson.
She suggested several possible causes for the warm waters in the fjords:
- Some of this ocean water that feeds them was initially warmed in the heatwave of 2014-16.
- This water is trapped in the fjord until the next infiling, in a year.
- With winters warming, there are not as many cold wind events impacting the inlets as th4re were in the 1950s, 60s and 70s.
Links of Interest
- (Advanced Earth & Space Science) Deep Waters in British Columbia Mainland Fjords Show Rapid Warming and Deoxygenation From 1951 to 2020
- (Hakai) How the Blob Is Warming British Columbia’s Fjords
- (Hakai) The Blob Hides in the Deep
- (Cortes Currents) articles about, or mentioning the Hakai Institute
- (Cortes Currents) articles about Bute Inlet
Photo credits: (top) A picture of me on the Raincoast Foundation’s boat Achiever – taken by Katrina Pyne (podcast) A picture of Bryn Fedje and Chris Mackenzie deploying a CTD (sensor that measures temperature, salinity, and oxygen) from a Hakai boat – picture taken by Grant Callegari; (map) Bathymetric map of British Columbia’s central coast, highlighting station DC in Douglas Channel, station RI2 in Rivers Inlet, station KN7 in Knight Inlet, and station BU4 in Bute Inlet. Bathymetric data starting at offshore 200 m isobath (from https://www.ncei.noaa.gov) along the black lines are shown in inset for each station. – taken from Deep Waters in BC Mainland Fjords; Knight Inlet – picture taken by Jennifer Jackson
(This article was originally published on June 3, 2021, and reposted as part of the October 9th Cortes Currents broadcast on CKTZ.)
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