Arctic warming contributes to increase in Northeast Pacific marine heatwave days over the past decades

Abstract

The frequency and duration of marine heatwaves have been increasing with ocean warming due to climate change. In particular, the Northeast Pacific has experienced intense and extensive marine heatwaves since the late 1990s – characteristically called “the Blob”. Here, an investigation of satellite-derived and reanalysis data supported by idealized coupled model experiments show that Arctic warming plays an important role in the increase in Northeast Pacific marine heatwave days during boreal summers. Strong Arctic warming has acted to change the atmospheric circulation pattern over the Northeast Pacific and reduce the low-level cloud fraction from late spring to early summer. We show that the enhancement of solar radiative heat fluxes and reduced latent heat loss over a relatively large area has favored an increase in sea surface temperatures and marine heatwave days. An idealized model experiment performed here, designed to isolate the impact of Arctic warming, supports this hypothesis. The projected changes of Arctic climate on the occurrence of marine heatwaves should be considered in climate change adaptation and mitigation plans.

On the persistence of near‐surface temperature dynamics in a warming world

“…We also documented an important difference in the measure of persistence for land and oceans, the measure being much larger for the latter, where large increases in marine heatwaves have been documented and are projected to increase. [20][21][22][64][65][66] Our study indicates the importance of accounting for or purging the effect of trends and noise. A popular way to assess changes in persistence is to detect in temperature series an increasing pattern of consecutive days above a fixed threshold value based on some upper quantile of the empirical distribution of temperatures over a fixed reference period.…”

“…This finding has important implications for projecting key climate variables. We also documented an important difference in the measure of persistence for land and oceans, the measure being much larger for the latter, where large increases in marine heatwaves have been documented and are projected to increase 20–22,64–66 …”

“…While the first two have received significant attention, 13–15 studies about the effects of changes in persistence on the probabilities of occurrence of extremes are much scarcer 16–18 . However, recent events with seemingly larger than usual duration, magnitude, and frequency 19 have invigorated research efforts for better understanding of the influence and nature of trends, changes in variability, and persistence over extremes 15,18,20–25 . However, to obtain an adequate estimation of persistence, it is crucial to properly account for trends and noise.…”

“…[16][17][18] However, recent events with seemingly larger than usual duration, magnitude, and frequency 19 have invigorated research efforts for better understanding of the influence and nature of trends, changes in variability, and persistence over extremes. 15,18,[20][21][22][23][24][25] However, to obtain an adequate estimation of persistence, it is crucial to properly account for trends and noise. As discussed in the time-series literature, not accounting for trends or structural changes can bias persistence estimates upward, while the presence of noise imparts a downward bias.…”

Distinct anthropogenic greenhouse gas and aerosol induced marine heatwaves

“…This striking trend requires a nuanced understanding of the multifaceted factors driving these phenomena. The complex dynamics of MHWs encompass a confluence of contributing variables, such as atmosphere circulation (Chen et al 2014(Chen et al , 2015, air-sea interactions (Schlegel et al 2021), ocean circulations (Elzahaby et al 2021, Ren and, climate variability (Oliver et al 2018, Holbrook et al 2019, Ren et al 2023, Arctic amplification (Song et al 2023) and anthropogenic climate change (Frölicher et al 2018, Barkhordarian et al 2022.…”