As oceans warm, marine cold spells are disappearing
Cold spells can harm ecosystems, but they can also provide critical
respite in warming oceans

Date:
March 17, 2022
Source:
American Geophysical Union
Summary:
Marine cold spells are cold versions of heat waves: periods of
exceptionally cold water, able to hurt or help the ecosystems
they hit.

Today, the oceans experience just 25% of the number of cold spell
days they did in the 1980s, and cold spells are about 15% less
intense, researchers found. Weaker cold spells could mean they're
less likely to cause mass die-off events, but having fewer cold
spells also means refuges and recovery periods from marine heat
waves are disappearing.



FULL STORY ========================================================================== Marine cold spells are cold versions of heat waves: periods of
exceptionally cold water, able to hurt or help the ecosystems they
hit. As the atmosphere and oceans warm, marine cold spells are becoming
less intense and less frequent overall, according to a new study.


========================================================================== Today, the oceans experience just 25% of the number of cold spell days
they did in the 1980s, and cold spells are about 15% less intense,
researchers found.

Weaker cold spells could mean they're less likely to cause mass die-off
events, but having fewer cold spells also means refuges and recovery
periods from marine heat waves are disappearing.

The study was published in the AGU journal Geophysical Research Letters,
which publishes short-format, high-impact research with implications
spanning the Earth and space sciences. It is the first study to quantify
and compare the changing nature of marine heat waves and cold spells
over several recent decades on an oceanwide, global scale.

"Recently, studies have focused on heat waves and warm ocean temperature events, less so the cold events," said lead author Yuxin Wang, an
ocean and climate scientist at the University of Tasmania. Because
marine cold spells have both positive and negative impacts, Wang said, understanding when, where and why these spells occur is critical for
predicting their presence in the future. Predicting cold spells could
be important for fisheries' long-term planning and for ensuring catch
limits are sustainable.

"Extreme events, either warm or cold, can bring an ecosystem to the
edge," said Sofia Darmaraki, a physical oceanographer at the National
and Kapodistrian University of Athens who was not involved in the
study. "Establishing the oceans' baseline climatology and sensitivity
of heat waves and cold spells to temperature changes, like they did
in this study, is a burning question for the community." Marine heat
waves, like heat waves over land, are natural phenomena becoming more
frequent and intense in some places as a result of anthropogenic climate change. Similarly, marine cold spells are natural, but their rates
are changing around the world. Over the past decade, cold spells have
occurred roughly 10 days per year globally, a notable drop from about
40 days per year in 1985.

To understand when and where marine cold spells occur and how those
patterns have changed over time, Wang and her colleagues analyzed sea
surface temperature data from 1982 to 2020, checking for periods of either extremely hot or cold temperatures. They found the oceans are warming, corresponding to global warming trends, and sea surface temperatures are becoming variable over time. That variability leads marine heat wave
and cold spell intensities to change at different rates, complicating scientists' attempts to predict each.

Establishing global trends in marine cold spells and their relationship
to global warming is an important step, but further studies are needed
to constrain regional and local effects, Wang said. Those local effects
include impacts on fisheries, which can be positive or negative.

"Marine cold spells play dual roles in influencing ecosystems," Wang said.

"They can cause devastating impacts, like coral bleaching and mass
mortality events. But cold spells can offset the impacts of heat waves." "Extreme events affect coastal communities and economies, but members
of the public might not be aware of how they're going to intensify in
the future. We need to get the word out," said Darmaraki. "Information
about the underlying physical causes of these extreme events can
help improve forecasting, which can lead to the development of early
warning systems. That information can be provided to fisheries and
other stakeholders, and they can collaborate on the best adaptations,
the best path forward." The better communities know what to expect,
the better they can prepare.


========================================================================== Story Source: Materials provided by American_Geophysical_Union. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Yuxin Wang, Jules B. Kajtar, Lisa V. Alexander, Gabriela S. Pilo,
Neil J.

Holbrook. Understanding the Changing Nature of Marine
Cold‐Spells.

Geophysical Research Letters, 2022; 49 (6) DOI: 10.1029/2021GL097002 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220317163403.htm

--- up 2 weeks, 3 days, 10 hours, 51 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)