Natural cycles in the Gulf of Alaska accentuate ocean acidification


Date:
September 15, 2021
Source:
University of Alaska Fairbanks
Summary:
New research shows that the fluctuations of major wind and ocean
circulation systems can temporarily accelerate or reverse the rate
of ocean acidification in the Gulf of Alaska.



FULL STORY ==========================================================================
New research at the University of Alaska Fairbanks shows that the
fluctuations of major wind and ocean circulation systems can temporarily accelerate or reverse the rate of ocean acidification in the Gulf
of Alaska.


==========================================================================
"We typically think of ocean acidification as this slow press onto the environment that gradually changes the carbon chemistry in the ocean," explained Claudine Hauri, a researcher at the UAF International Arctic
Research Center.

Instead, Hauri said, the research shows that the chemical conditions experienced by marine organisms can change on a daily and seasonal
basis. This fluctuation occurs despite a long-term trend of ocean
acidification connected to the steady rise in atmospheric carbon dioxide concentrations. The new research also documents massive cycles that
happen every five to 10 years.

"Chemical conditions will deteriorate for several years in a row in
offshore areas, before stabilizing or even slightly improving again,"
said co-author Andrew McDonnell from the UAF College of Fisheries
and Ocean Sciences. "We don't know exactly how organisms respond to
that, but in general some organisms are sensitive to these types of
changes in environmental conditions." Hauri and her team examined ocean acidification through a model that combines physical, biogeochemical and hydrological ocean models to reproduce past Gulf of Alaska conditions
from 1980-2013.

The study identified natural decadal fluctuations in chemical conditions
that are driven by the strength of the North Pacific subpolar gyre.

This gyre is a large wind-driven system of circulating ocean currents
affecting the Gulf of Alaska. When the gyre is strong, it brings more
deep water rich in carbon dioxide to the ocean's surface. This can
accelerate ocean acidification, creating extreme events that cause stress
to sensitive organisms. When the gyre is weak, less carbon is delivered
to the surface, which can dampen the ocean acidification effect or even
reverse it.

From 2011 to 2013, the model showed a strong phase of the gyre resulted
in an extreme ocean acidification event in the center of the Gulf of
Alaska. This event preceded the 2014-2016 "blob" of exceptionally warm
water in the same region.

"The blob followed right after this very strong ocean acidification
event," Hauri explained. "First, some organisms were probably stressed
because of ocean acidification, and then they were hit right after with
heat." Hauri emphasized that more research is needed to understand the consequences of multiple simultaneous stressors on marine ecosystems,
and to identify how ocean acidification and climate change interact.

Another implication of this work is that multiple decades of observational
data are necessary to separate out the long-term trend of ocean
acidification from the natural variability driven by the strength of
the subpolar gyre. This type of dataset does not currently exist for
the Gulf of Alaska.

Hauri and her team hope that this work and the efforts it prompts
will provide needed information for people engaged in subsistence and commercial fisheries as they plan and adapt for the future.

========================================================================== Story Source: Materials provided by
University_of_Alaska_Fairbanks. Original written by Heather
McFarland. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Claudine Hauri, Re'mi Page`s, Andrew M. P. McDonnell, Malte
F. Stuecker,
Seth L. Danielson, Katherine Hedstrom, Brita Irving, Cristina
Schultz, Scott C. Doney. Modulation of ocean acidification by
decadal climate variability in the Gulf of Alaska. Communications
Earth & Environment, 2021; 2 (1) DOI: 10.1038/s43247-021-00254-z ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210915085837.htm

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