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Warmer ocean temps and future storms in NL

An iceberg floats in a harbour while lobster pots are stacked in the foreground. As ocean temperatures climb, there is an acceleration in the loss of sea ice. – © Rosalyn Roy / Wreckhouse Press Inc.

By Jaymie L. White Local Journalism Initiative Reporter

According to an article published by CNN on May 5, 2023, (‘Ocean temperatures are off the charts right now, and scientists are alarmed’) the heat on the surface of the ocean is at record-breaking levels and temperatures began to climb in mid-March. The ocean temperature is nearly two-tenths of a degree higher than the previous record in 2016, and since the peak in April, temperatures have climbed higher than ever recorded for this time of year. According to Eddie Sheerr in a post-Fiona interview, warmer than usual ocean temperatures were a factor in the severity of that storm. “The ocean temperatures this year, being so abnormally warm so far north, allowed the storm to maintain Category 4 strength for much longer than any storm previous to that, in the history of the Atlantic hurricane basin. So that did play a role in the storm being so impactful to the region. Once any storm gets north of Bermuda, even though it is still a strong hurricane, it will begin to undergo what is called Extra-tropical transition, which means it will start to lose its tropical characteristics and become more of a different structured cyclone. But just because it is called a post-tropical storm doesn’t have anything to do with strength,” said Sheerr. “What people need to understand is it has to do more with structure than actual strength. Typically they are not as strong, but every so often you will get one that is.” Environment and Climate Change Canada (ECCC) confirmed there has been a trend of increased ocean temperatures. “It is virtually certain that the global ocean has warmed unabated since 1970 and has taken up more than 90 per cent of the excess heat in the climate system (high confidence). Since 1993, the rate of ocean warming has more than doubled (likely). Marine heatwaves have very likely doubled in frequency since 1982 and are increasing in intensity (IPCC SROCC Summary for policymakers A.2). Ocean warming is directly observed by ships, autonomous robot floats and satellites. “Average ocean surface temperatures since mid-March 2023 have been warmer by a large margin than in any previous year since at least 1850. According to the National Oceanic and Atmospheric Administration (NOAA), ocean surface temperatures in May were 0.85∞C above the 1901-2000 average, and 0.08∞C above the previous record for May in 2016, after temperatures worldwide had been elevated by a strong El Niño. Although complete data for June is not available yet, the previous record for June is on track to be broken by an even larger margin, and the currently developing El Niño will likely continue to push ocean temperatures into uncharted territory through 2024.” There are several dangers that can be associated with increased ocean temperatures. “Increased storm intensity: Ocean warming influences weather that people experience. For example, warmer oceans provide additional energy that fuels hurricane intensity, and more generally warmer temperatures lead to more evaporation and extreme precipitation,” stated ECCC via email. “Sea-level rise: As the ocean warms it expands, leading to sea-level rise. Warmer oceans also accelerate melting of marine terminating glaciers, which drives loss of ice mass from Antarctica and further sea-level rise. Sea-level rise has major impacts on coastal and low lying island communities. Together with intensification of storm activity and the associate storm surge, sea-level rise is a major risk for coastal flooding. Then there are the ecosystem impacts, including to marine species. “Warming oceans affect marine species, many of which have specific temperature requirements for their survival and reproduction. As the oceans warm, species are observed to be migrating poleward, and where species cannot migrate or adapt, they face extinction. Coral bleaching is one such example of ocean warming on ecosystems. Reduced oxygen levels: Warm waters hold less oxygen, and ocean warming is increasing the volume of low or no oxygen waters in the ocean, that can harm some marine organisms (such as fish, shellfish, etc.)” The climate, including sea ice, is also affected by warmer than normal ocean temperatures. “Warmer oceans contribute to loss of sea-ice cover, which accelerates warming of the climate, and impacts ice-dwelling ecosystems, and also affects shipping routes.” The ocean can only take so much. “Ocean warming is mostly driven by human emissions of carbon dioxide. The oceans absorb about 30 per cent of these human emissions each year, which helps to reduce the climate warming we experience. However, this absorption of carbon dioxide causes ocean acidification, with impacts for marine ecosystems, particularly shellfish or organisms containing calcium carbonate.” ECCC explained that the entire planet is impacted. “The circulation of the atmosphere (winds) and ocean (currents) are sensitive to temperature. With warming, these circulations can be altered, which in turn alters regional climates that people experience. For example, warming is known to cause an expansion of the tropical Hadley cell in the atmosphere and a poleward shift of the Southern Hemisphere westerly winds, which are the strongest time-averaged winds on the planet, and influence precipitation (water availability) in Southern Hemisphere countries, such as South Africa and Australia. As the oceans warm, they are less able to absorb this carbon dioxide, which acts also to worsen human caused climate change, because more CO2 remains in the atmosphere than it would without warming.” With these warmer temperatures, ECCC added that storms like Hurricane Fiona would be more likely to appear this far north. “The linkage between hurricanes in the tropics and water temperature is quite clear as hurricanes feed off warm water. In Atlantic Canada, however, it’s slightly more complicated given the many storms that become post-tropical prior to reaching the region. A post-tropical storm is one that no longer gets the majority of its energy from the warm water but rather from temperature differences in the atmosphere. Warmer waters around Atlantic Canada could mean that under certain scenarios an approaching hurricane may weaken slower that it would with cooler water temperatures, but it does not mean that every storm will be stronger. In the case of Fiona, warmer water did manage to keep the hurricane stronger farther north, however, the other key factor in the storm’s intensity was its interaction with another weather feature approaching from Quebec.” Unlike in more tropical climates, the Atlantic shouldn’t see stronger hurricanes as a result of warmer temperatures. “Typically in the tropics, with everything else being equal, hurricanes will get stronger as the water gets warmer. However, in Atlantic Canada, despite the observation of warmer waters, they still are not warm enough to cause hurricanes to get stronger here. Rather the warmer waters here will only cause a reduction in the rate of weakening. That said, storm intensification is still possible, but not as a hurricane, but as a post-tropical storm, which as mentioned above would be due to other factors.” The ECCC said ocean temperatures are something that can be predicted to a certain degree. “The long-term increase in average ocean temperatures is caused primarily by the increase in heat-trapping greenhouse gases in the atmosphere, and is well represented in climate models. El Niño events cause additional temporary increases in ocean temperatures on top of this trend which can be predicted around a year in advance. Additional regional warming, such as the current unprecedented ocean temperatures in the eastern North Atlantic, can be caused by a variety of factors including weather patterns, and may be predictable weeks to months ahead.” ECCC stated that NOAA issues regular forecasts for marine heat waves informed by the North American Multi-Model Ensemble, a set of six seasonal forecast models that includes two from ECCC. In response to email inquiries, Fisheries and Oceans Canada (DFO) confirmed that the North Atlantic is currently experiencing increased marine temperatures. “The North Atlantic is, on average, experiencing above normal sea surface temperatures that likely qualify as the definition of a marine heat wave. The situation can change in a matter of a few weeks in terms of swinging from positive to negative anomalies, or vice versa.. For example, at the end of June, the warm anomalies were on the East side of the North Atlantic. The marine heat wave has recently lessened in intensity closer to Europe, but has begun in full force on the Canadian side of the North Atlantic.” There isn’t a single cause to pinpoint, however. “There could be a number of reasons why the Atlantic is so warm right now, including less dust in the atmosphere, increasing the amount of solar radiation that reaches the ocean. On the Canadian side of the Atlantic, summer water temperatures are mostly reacting to air temperatures with dominant westerly winds bringing continental air masses over the water.” With the increased temperatures, DFO stated that there are negative impacts to marine life. “Many marine resources have been negatively impacted by increasing ocean temperatures, but there is considerable variability in the nature of the effects. Most of the cold water species (i.e., shrimp and crab) can have the extent of the suitable habitat reduced as a result of increasing water temperatures, particularly when bottom water temperatures increase. There are optimal ranges for each species/stock, which in some instances can result in expansions of the available habitat but in many instances, optimal areas have declined in their extent. There are unknown physiological constraints that can also affect their productivity. These factors can be compounded by changes in the abundance and activity of predators (e.g., groundfish, redfish) that can add increased pressure on the populations.” According to DFO, if the same trend continues, minor increases could be predicted for the next five or ten years. “The long-term warming trend (150 years) of the summer time sea surface temperature over the Canadian Atlantic zone is 1.1 Celsius per 100 years over the Gulf of St. Lawrence, about the same over the Scotian Shelf and possibly more over the Labrador and Newfoundland Shelf. However, this increases to 3.7 Celsius per 100 years over the Gulf since 1990. But that’s still a fairly small increase over 5 to 10 years and inter-annual variability is quite strong, wiping out detection of the trend over such a short time.”

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