Observed Climate Associated Impacts

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].

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].