• Rocky intertidal shores are some of the most physically stressful habitats on Earth, and
  • many of the species that occupy them often live very close to their physiological tolerance limits.
• Intertidal ecosystems are therefore often used as bellwethers for the ecological effects of
  • climate change and
  • extreme weather events.
• Plants and animals that live in the intertidal zone are especially susceptible to extremely high temperatures during daytime low tides,
  • when solar radiation can raise organismal body temperatures well above air temperature.
• The hottest days of the 2021 heatwave coincided with
  • very low, early afternoon low tides throughout most of the Salish Sea (the inland waters of BC and Washington State).
• As a result, surface temperatures in excess of 50 °C were observed in the intertidal zone,
  • particularly on gently sloping south and west-facing surfaces that received the most direct solar radiation.

paraphrase

• This event was widely described in the media as a “heat dome”, wherein
  • subsidence/adiabatic warming,
  • “trapped air”, and
  • sensible heating
• are the dominant mechanisms driving the anomalous heat.
• This conceptual model ignores the role of upstream diabatic heating,
  • which our analysis
• shows is a significant heat source.
• This “heat dome” phrase is not a common phrase within the scientific community

comment

• the authors do not refer to this event as a heat dome, as is popularly used in the media because diabatic heating was involved

• near-term forecasts of this event were good, albeit underestimating the magnitude of the maximum temperatures.

• could appropriate measures have been in taken, our were the predicted temperature so far off that appropriate measures could not be recommended?
• in particular, with the mass dieoff from the marine heatwave of an estimate billion marines organisms due to:
  • low tide,
  • high surface air temperature and
  • elevated ocean temperatures,
• could interventions have been organized such as:
  • increasing dissolved oxygen levels in parts of the ocean dense with sea life or
  • soaking shellfish exposed to extreme sea surface temperature?
• what are the future impacts in terms of biodiversity loss and extinction?

• An unprecedented heatwave occurred in the Pacific Northwest (PNW)
  • from ~25 June to 2 July 2021,
  • over lands colonially named
    • British Columbia (BC)
    • Alberta (AB) in Canada,
    • Washington (WA),
    • Oregon (OR) in the United States.
• Near-surface air temperature anomalies reached up to 16–20 °C above normal over a wide region (Fig. 1),
  • with many locations breaking all-time maximum temperature records by more than 5 °C (Fig. 2a).
• The Canadian national temperature record was broken 3 days in a row, at multiple locations,
  • with the highest temperature of 49.6 °C recorded in Lytton, BC, on 29 June (Figs. 1b),
  • 4.6 °C higher than the Canadian record prior to this event.
• The new record temperature was reportedly the hottest worldwide temperature recorded north of 45° latitude,
  • and hotter than any recorded temperature in Europe or South America.