The coastal West differs regionally in climate and oceanography throughout the period
By LILLY ACKERMAN — science@theaggie.org
A recent study out of UC Davis is the first of its kind in synthesizing climate and oceanography records. It drew records from individual regions in the coastal Western United States into a comprehensive paper that covers changes in the entire region throughout the Holocene.
The Holocene is the most recent geological epoch, or division of geologic time, spanning the last 11,750 years and continuing through today. Despite the fact that it encompasses the present, the Holocene is still relatively understudied in the world of geology.
Veronica Padilla Vriesman, the second author on the study, recently earned her Ph.D. from UC Davis in the Department of Earth and Planetary Sciences. She explained why this synthesis paper was necessary.
“It’s interesting; [the Holocene is] the most recent geological interval, but in some ways, it’s the least understood geologically,” Vriesman said. “[G]eologists tend to focus on millions of years ago, and biologists and ecologists tend to focus on seasons. So this is kind of the in-between timescale.”
According to Vriesman, the inspiration for the study came out of a graduate seminar led by Professor Tessa Hill in the Department of Earth and Planetary Sciences.
“We were looking into climate patterns over the past 10,000 years along the Pacific and the West Coast of North America,” Vriesman said. “And we realized that the paper we were hoping to read didn’t exist, so this paper kind of became a project out of what was missing from the literature.”
The study’s lead author, Hannah Palmer, who graduated with a Ph.D. in earth and planetary sciences from UC Davis in 2021, noted that the study found significant variations in climate patterns, ocean productivity and dominant tree types for coastal Western North America at different times during the Holocene.
According to Palmer, three main subsections within the Holocene can be differentiated, beginning with the early Holocene. This time period was characterized by warmer and drier conditions and reduced coastal fog. It also featured pine-dominated coastal forests (unlike the redwoods we are used to today) and reduced ocean upwelling and productivity, meaning there was decreased synthesis of organic matter and respiration from surface species like phytoplankton that support the consumers in the ocean.
During the middle Holocene, the region began to transition away from the dry and warm conditions.
“In the Middle Holocene, the region was wet and cool and the conditions we see today began to develop during this time (8,200-4,200 years before present), including an increase in coastal upwelling and ocean productivity and an increase in coastal fog and coastal redwoods,” Palmer said via email.
Finally, the late Holocene features characteristics we are used to today.
“The Late Holocene is the most variable interval, both spatially and temporally, and a novel spatial trend appears in terrestrial climate with warmer coastal areas and cooler inland areas,” the study reads.
The study also found a marked change in several environmental factors within the last few hundred years, a time period referred to by Palmer as the “Era of Colonization.”
“A critical finding of this study is the signature of human impacts on the climate and environment beginning several hundred years ago at the onset of settler colonization and continuing through to today,” Palmer said. “Notable changes include changes in fire
activity, shifts in pollen and vegetation composition, landscape change (such as movement of
sediments and changes in the chemistry of sediments), and changes [in] marine resource use.”
The authors hope that their study, which puts together several pieces of the complicated history of the Holocene, can help inform decisions and further research in the face of a changing climate.
“The patterns identified here can inform how we predict and plan for future climate change,” Palmer said. “Further, I hope this study informs future work [that studies] human-environment interactions.”
Written by: Lilly Ackerman — science@theaggie.org
