Globally, dissolved oxygen levels in the ocean have been declining for more than two decades [53]. Declining ocean oxygen levels (hypoxia) is linked with both ocean warming and changing ocean currents, as well as excessive nutrients leading to eutrophication and organic matter decomposition. Oxygen is also less soluble in warmer water, which combined with thermal stratification is predicted to lead to ocean de-oxygenation globally [54]. In the Pacific Ocean, dissolved oxygen levels have been declining over at least the past several decades, at a range of depths from 100-1000m deep down to the sea floor, and oxygen levels between 100-400m depth have decreased by 22% over the past 50 years [5].
Climate change trends have in turn affected coastal ecosystems and economic sectors in BC. As of 2017, some observed impacts that may be associated with climate change trends include both general and specific examples.
Ecosystems
Changing ocean temperatures affect marine species, ecosystems, and the human communities and economic sectors that depend on marine resources. Warming ocean temperatures have been observed with associated impacts on the marine ecosystem and fish, for the past several decades [56]. Increasing sea surface temperatures and declining oxygen levels have affected the northern Pacific Ocean, which has likely led to reduced habitat availability and decreased survival for many fishes and invertebrates [57].
Harmful algae blooms during the 2015 ‘warm blob’ event could also be associated with climate warming [58]. During that event, warm water zooplankton were much more abundant than cold water species in 2016. Changing zooplankton species has potential implications for fish, as warm water zooplankton species have lower nutrient quality [58]. Other unusual biological events during that anomalously warm water period included low chlorophyll levels (2014), potentially due to increased stratification and reduced nutrients [59]. This mass of abnormally warm water has since dissipated (in 2016) [11].
Abnormal warm water species sightings that could indicate dramatic species range shifts include sightings of ocean sunfish and warm water sharks off Washington State and Alaska, high catches of albacore tuna off the Washington and Oregon coasts, juvenile pompano sightings near the Columbia River, and widespread stranding of Velella velella off the coast of BC throughout the summer of 2014 [13].
The physical oceanographic impact of increased ocean temperature has had substantial impacts on the marine ecosystem, suggesting that long-term climate warming may have analogous ecosystem responses [13].
Hakai | Photo by Charles Short
Fisheries
Fisheries catches and landed values have declined since the 1990s in BC [56]. A warming trend in sea surface temperatures was detectable even several decades ago [56]. In southern BC, the impacts of warming freshwater and marine water temperatures have been observed, leading to declining fish productivity and diminished returns of Fraser River sockeye salmon [25]. Ocean acidification has been observed in BC, especially along the south coast [61–63]. Increasing rates of acidification are likely to negatively affect calcifying organisms, many of which are important for aquaculture and traditional food resources, including molluscs, bivalves, sea urchins, and sea cucumbers. While observations and field evidence are still limited, the interacting effects of ocean temperature and acidification is of critical concern for many taxa (e.g. molluscs, corals, calcareous algae).
Warm sea surface temperatures have been observed, along with warm water associated species shifting north into BC waters [13].
Ocean acidification has affected calcifying organisms, especially larval survival (e.g. Strait of Georgia [61–63]).
Warm ocean temperatures, combined with summer drought, have created unfavorable conditions for salmonids. Low returns of Fraser River sockeye salmon have been observed (e.g. returns in 2016 were the lowest on record) [64]. Fraser River sockeye were recently recommended for listing with the Species at Risk Act [65].
Melting glaciers across BC may be releasing historical pollutants into freshwater ecosystems, thus affecting freshwater fish and downstream marine areas [66].
Human Communities
Clam shucking | Photo by Scott Harris
Energy demands for heating have declined for buildings across BC, especially in northern BC, as average air temperatures have increased [10].
Increasing storm surge events have been observed along the BC coast, along with an increasing frequency of ‘king tide’ events.
First Nations cultural sites may be impacted by rising sea levels, storm surge, and king tide events. For example, cultural sites near Prince Rupert and Metlakatla are experiencing erosion and loss of cultural artifacts (A. Paul, pers. comm., November 24, 2017).
First Nations communities have observed changes to seasonality of local food gathering practices [67].
Marine infrastructure
Increasing sea levels may be affecting coastal built infrastructure [68,69].
Increasing frequency and intensity of storm events may affect marine infrastructure (at sea and near-shore) [25].
Empirical data from lighthouse station monitoring stations in 2016 reflect a long-term trend towards decreasing sea surface salinity (SSS) across the BC coast, except within the Strait of Georgia (Chandler 2017). Longer term data from lighthouse station monitoring shows the same freshening trend; however, this is not associated with longer term climate trends, but with local freshwater sources [55].
Wooden Fish weir, Knight Inlet | Photo by Barb Dinning
Ocean acidification is caused by the dissolution of atmospheric carbon dioxide into the oceans, which results in a decrease in seawater pH and increased acidity [46]. Since the pre-industrial era, the oceans have absorbed approximately one-third of human produced carbon dioxide emissions, resulting in an increase in acidity of more than 26%, the lowest levels in 20 million years [46–49]. The impacts of acidification on marine ecosystems are complex and serious, especially for calcareous and planktonic organisms as it impacts the ability of those organisms to produce and maintain their calcium carbonate shell structures [46,50] as well as potentially increases metabolic stress.
In the Northeastern Pacific Ocean, ocean acidification is one of the most urgent threats to both marine ecosystems and human communities. These waters are already among the most acidic of the world’s ocean regions, due to ocean currents and upwelling of deep ocean waters [5,51,52]. Upwelling waters already have relatively low pH, and organic matter production driven by upwelling currents further lowers the pH of those waters by remineralization.
Sea surface temperatures are monitored at lighthouse stations along the BC coastline. Average annual sea surface temperatures have warmed between 0.6 to 1.4⁰C per century across the coast of BC [10]. This rate is similar to the global average of 1.1⁰C per century [10,32], although there is significant variation along the BC coast in that some areas have warmed by up to 2.2⁰C per century (e.g. Strait of Georgia, Entrance Island) [10].
In BC waters, recent sea surface temperature trends have been the result of the interaction of three things: climate change warming, El Niño effects (2015-2016), and the ‘warm blob’ phenomenon (2013-2016) where a large area of very warm water (3⁰C warmer than usual) settled off the BC coast [13,45]. In 2016, average sea surface temperatures were 1-2⁰C warmer than the historical average within the Northeastern Pacific Ocean [11]. The average daily sea surface temperature anomaly was higher in 2016 according to both lighthouse station data (0.98⁰C ± 0.33⁰C) and weather buoy data (0.7⁰C average) as compared to the 22-year historical average (1989-2010), which reflects the long term warming trend [11].
Sea level rise is the direct result of warming temperatures that trigger increased melting of glaciers and ice caps, as well as the thermal expansion of warming oceans [44]. Glacial coverage in BC has declined since 1985, and the volume of glacial ice declined by an average rate of 21.9 km3 from 1985-2000 [10]. In the coastal mountain area of BC, which includes the MaPP region, glacier area decreased by approximately 6.4% from 1985-2000 [10]. Sea levels are also affected by ocean and weather patterns such as wind, currents, and salinity, and also by subsidence and uplift of the adjacent land mass due to geological processes. Changes in sea level threatens coastal systems through coastal erosion, seawater inundation, contamination of freshwater systems, and can affect food crops grown in low lying areas.
Global mean sea levels increased 10-20 cm during the 20th century, and have been increasing by 3.2 mm/year since 1993 [32,36]. In BC, the average sea level between 1910-2014 has risen along most of the coast, at a rate of 13.3 cm/century at Prince Rupert, 6.6 cm/century at Victoria, and 3.7cm/century at Vancouver [10]. Sea levels at Prince Rupert and Victoria continue to increase, while off the west coast of Vancouver Island tectonic uplift (isostatic rebound from the weight of ice age glaciers) offsets sea level rise such that water levels appear to be declining (removing this uplift would result in a sea level increase of 13.5 cm per century) [10,11].
Precipitation is a key indicator of climate change, and changes in precipitation will affect all sectors, ecosystems, and communities. In BC, precipitation has increased over the last 50 years in all seasons by some estimates, or just in the summer months by other reports, with variation across the province [5,25,41]. Province-wide, annual average precipitation has increased by 12% per century [10]. However, these changes have been so far statistically insignificant and can largely be explained by the high natural variation in precipitation patterns across the province [10,42,43]. Winter warming trends led to higher snowpack density (wetter snow) across much of BC from 1950-2014, and as winter temperatures increase, winter snows are likely to continue to be wet and heavy, or even fall as rain [10]. This trend has not yet been significant for the BC coastal region that includes the MaPP region [10].
Changes in the amount, type, and timing of precipitation in BC will certainly affect both terrestrial and marine systems, although the relatively high uncertainty in historical monitoring data means that estimating current precipitation trends and associated impacts is a challenge [10]. In 2016, precipitation levels were higher than average for most regions in BC [11].
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Written by Charlotte K. Whitney and Tugce Conger
Whitney, Charlotte, and Tugce Conger. 2019. “Northern Shelf Bioregion Climate Change Assessment: Projected Climate Changes, Sectoral Impacts, and Recommendations for Adaptation Strategies Across the Canadian North Pacific Coast.”
Written by Charlotte K. Whitney, Tugce Conger, Natalie C. Ban, and Romney McPhie
Charlotte K. Whitney, Tugce Conger, Natalie C. Ban, Romney McPhie, and Steven J. Cooke. Synthesizing and communicating climate change impacts to inform coastal adaptation planning. FACETS. 5(1): 704-737. https://doi.org/10.1139/facets-2019-0027
