Xinru Li1 and Simon
Donner11. Department of Geography, University of British Columbia, Vancouver,
B.C., Canada
Corresponding author: Xinru Li
(xinrulicco@gmail.com)
Key points
- There are considerable regional biases in the thermal properties of
warm-season marine heatwave in three CMIP6 models
- Models biases in the thermal properties are likely caused by different
model representations of related atmospheric and oceanic processes
- In contrast to duration, accumulated heat stress and peak intensity,
heating rate and “priming” duration are projected to decline by 2100
AbstractMarine heatwaves in the summertime when temperatures may exceed
organisms’ thermal thresholds (“warm-season MHWs”) have huge impacts
on the health and function of ecosystems like kelp forests and coral
reefs. While previous studies showed that MHWs are likely to become more
frequent and severe under future climate change, there has been less
analysis of the thermal properties of warm-season MHWs or on the effects
of climate model biases on these projections. In this study, we examine
CMIP6 model ability to simulate five key thermal properties of
warm-season MHWs, and evaluate the global pattern of future projections
for coral reef and kelp systems. The results show that the duration,
accumulated heat stress and peak intensity are projected to increase by
> 60 day, 160 °C·day and 1 °C, respectively, across most of
the ocean by the end of 21st century. In contrast, the
duration of “priming” (a period of sub-lethal heat stress prior to MHW
development) is projected to decrease by > 30 day in the
tropics, potentially reducing organisms’ ability to acclimate to heat
stress. The projected increases in the MHW duration and accumulated heat
stress in some coral reef and kelp forest locations, however, are likely
overestimated due to model limitations in simulating surface winds, deep
convections and some other processes that influence MHW evolution. The
findings point to the processes to target in model development and
regional biases to be considered when projecting the impacts of MHWs on
marine ecosystems.