Come rain or come shine: How is climate change impacting precipitation along Kachemak Bay?
Last year in Homer, a warm, dry spring gave way to a very damp, gray summer. For Paul Castellani of Will Grow Farm, handling whatever the weather brings is business as usual. He and his wife Jen have been growing vegetables at their property near Anchor Point for two decades.
“It wasn't an extraordinary summer,” Castellani said, “except for the way that the two types of conditions were so separated.”
The early dry spell meant the Castellanis had to pay close attention to irrigating their carrot beds to make sure the seeds stayed moist, although cool, clear nights offered their crops some much-needed morning dew. But by the end of the season, getting their storage onions to cure with the cloudy, rainy conditions was a challenge.
Weather patterns aren’t always clear cut on the Kenai Peninsula. Temperatures and precipitation can vary drastically at different elevations. Castellani said there are times when a nearby farm higher up in the hills may get an inch of rain, while his property sees only a steady drizzle.
“I've had summers when they did just fine, and my lower field just flooded completely — I didn't even get to plant until July. So it goes both ways, for sure,” he said.
That natural variability speaks to the challenges Rick Thoman faces in his role as a climate specialist at the Alaska Center for Climate Assessment and Policy at the University of Alaska Fairbanks. Alaska is a huge state with diverse ecosystems, and climate change is having different effects across its many regions.
“We're seeing less precipitation in the summer over the last 50 years over the Alaska Peninsula,” Thoman said, “but a dramatic increase in precipitation in the summer across the eastern Gulf Coast into Southeast Alaska.”
While most areas of the state have seen an increase in precipitation over the last half-century, rainfall can be quite different from year to year.
“Everybody's going to see more, but any given week or month or season can be very different,” Thoman said.
In general, Thoman explained that as oceans warm, more moisture evaporates from its surface into the atmosphere. When storm systems come along with the right atmospheric conditions, the additional water vapor makes extreme precipitation events more likely.
“Over the past several years, in Fairbanks, and of course, around the world, we have seen many instances of these extreme precipitation events, whether it's the 40 odd inches of snow in Anchorage in 11 days [in December], or the wettest year on record for both Anchorage and Juneau in 2022,” he said. “None of this is unexpected.”
In much of the state, he added, “annual precipitation is low enough that even just a few big storms can make a big difference.”
For farmers like Castellani, when rain falls is as important as how much. At lower elevations across Alaska, Thoman explained, autumn precipitation is now increasingly falling as rain rather than snow, as warm temperatures linger.
But a lack of data complicates Thoman’s job of forecasting what the future might hold. Alaska has very few observation points or weather stations at higher elevations — only a handful above 1,000 feet on the Kenai Peninsula. Alaska’s mountains play a huge role in local weather patterns.
“We don't have a good idea of what's going on in the mountains. And that ultimately is very important for things like snow melt in the spring,” he said, “which greatly impacts the ecosystem of the near-coastal environment. And so that is really a big problem, that lack of information.”
Knowing how weather might change locally, however, is what city planners and engineers need to know to prepare for a shifting climate — and that’s exactly the kind of information the Woodwell Climate Research Center hopes to provide. With ties to a Homer climate scientist, the organization offered to create a risk assessment for Homer and Seldovia to help assess and plan for the impacts of climate change on the coastal communities.
“Our goal with this work is to provide climate projections to communities that don't otherwise have the resources,” said Alex Naegele, a postdoctoral researcher in Woodwell’s climate risk group, who helped compile the report. .
The work encompassed both sides of Kachemak Bay, with the aim of spelling out Homer and Seldovia’s potential future climate risks.
Wildfire and flooding are at the top of that list. Both communities are “expected to see more drought in the future,” Naegele said. “But at the same time, we're going to be seeing more intense rain events, and more flooding.”
Both town’s airports are likely to be subject to flooding, and in Homer, the Spit — home to the harbor and central to the tourism season — may be increasingly inundated by storms.
That’s not a unique trend to the Kenai Peninsula, she explained, but an uneven distribution of rain and snow will have distinct impacts locally.
“The number of wildfire danger days will increase in the future as temperatures rise and drought worsens,” the researchers wrote.
Specific local factors — like trees killed by spruce beetles — also contribute to overall fire risk in the coming years, though the report points out that most fires on the Kenai Peninsula are caused by people.
Woodwell’s models also presented some short-lived surprises, Naegele said. Glacial ice sheets melting, for instance, will cause the earth to rise in a process called isostatic rebound. As a result, by 2050 “we're going to see actually less flooding and inundation.” But the effect will be temporary, she added. By 2080, additional precipitation will be causing more flooding.
Similarly, the researchers found that when average temperatures rise two degrees celsius, the Kenai Peninsula may temporarily see a slight decrease in wildfire risk.
“It's hard to say what exactly causes that, but it could be that there's maybe more precipitation in the future,” she said.
The fire season will also shift later in the year: wildfire risk currently peaks in July, but in the future, it will likely change to August.
“We often assume that things are going to progress linearly, or get worse in the same way, year after year, decade after decade. But this is a good reminder that these changes aren't always linear. And they can sometimes take us by surprise,” Naegele said.
Woodwell has only studied a handful of communities globally for this initiative so far, which gives Homer and Seldovia a unique view of future climate trends. Some of these changes are already evident to long-time residents. Thinking back over his nearly three decades here, Castellani said winters have noticeably changed. While every year is a little different, the ground seems to freeze later in October, and spring break up often comes earlier.
Thoman — the climatologist — encouraged Alaskan’s to help quantify those kinds of observations by collecting and sharing information on rain and snowfall online. For anyone interested in helping climate scientists gather data, Thoman suggested they look to Colorado State University’s Community Collaborative Rain, Hail and Snow Network for affordable rain gauges and straight-forward instructions.
On the Kenai Peninsula, Thoman said there were only a few observations coming in from around Soldotna, and none from Homer.
“We desperately need more snow and precipitation measurements,” he said. “People are still the very best way to get that information.”