In a study led by Naim Bautista, a postdoctoral researcher in Jay Storz’s lab at the University of Nebraska-Lincoln, the team took highland deer mice and their lowland cousins on a simulated ascent to 6,000 meters. The “climb” ventured from sea level and the mice reached the simulated summit seven weeks later. Along the way, Bautista tracked how the mice responded to cold stress at progressively lower oxygen levels.

“Deer mice have the broadest environmental range of any North American mammal, as they are distributed from the plains of Nebraska to the summits of the highest peaks in the Rocky Mountains and Sierra Nevada,” said Storz, Willa Cather Professor of biological sciences. “This study tested whether they are able to thrive across such a broad range of elevations by evolving adaptations to local conditions or by possessing a generalized ability to acclimatize.”

Conducted in a specialized lab at Canada’s McMaster University, the study divided each team of highland and lowland mice into two distinct groups — a control that remained at sea level throughout the study, and an acclimation group that embarked on the seven-week ascent.

After seven days at sea-level, conditions for the acclimated group advanced by 1,000 meters in elevation weekly, with oxygen levels reduced to reflect what climbers would experience. The research team monitored the ability of each mouse to cope with cold exposure by means of metabolic heat production.

Data showed that the highland and lowland deer mouse cousins do not share a general ability to acclimate to hypoxia (low oxygen conditions). As the simulated elevations rose above 4,000 meters, the homefield advantage of the highland mice quickly became apparent. As oxygen levels dropped, the highland mice were better able to regulate body temperature than their lowland counterparts owing to more efficient breathing and circulatory oxygen-transport.

“The results show us that the highlanders and lowlanders do not share a generalized ability to acclimatize to changing environmental conditions,” Bautista said. “Rather, the mice living at higher elevations share evolved ways to acclimatize to low oxygen conditions that are distinct from those of the lowland prairie mice.”

The study also showed that the highland mice have a genetic advantage that helps suppress thickening of the right ventricle of the heart, a symptom of pulmonary hypertension, which is a common malady among lowland mammals that are forced to acclimatize to low oxygen conditions.

Bautista said the findings show how adaptation to local conditions can allow a widely distributed species like the deer mouse to thrive in diverse environments.

“It highlights how evolved changes specific to populations help shape their flexibility,” Bautista said. “Ultimately, it is these changes that influence their ability to survive within different habitats.”

Bautista is finalizing plans to repeat the study, taking it to new heights by measuring the responses of the yellow-rumped leaf-eared mouse, the world’s highest-dwelling mammal. The species hails from the Andes mountains, living at elevations up to 22,110 feet, and was discovered by Storz.

The deer mice study was recently published in PNAS. Other members of the research team include Storz; Ellen Shadowitz and Graham Scott of McMaster University; Nathanael Herrera and Zachary Cheviron of the University of Montana; and Oliver Wearing of the University of British Columbia.

The discovery, detailed in a study in Current Biology, could inform a key strategy to protect the food supply in the face of climate instability, the researchers said. Agricultural productivity is particularly vulnerable to climate change, the study noted, and rising temperatures are predicted to reduce crop yields by 2.5% to 16% for every additional 1 degree Celsius of seasonal warming.

The scientists took some lessons from evolution to experiment with how best to speed up the adaptation process for varieties of tomato plants, explained study author Sorel V. Yimga Ouonkap, a research associate in molecular biology, cell biology and biochemistry at Brown. It would take a long time to wait for evolution to weed out the vulnerable tomato varieties like Heinz in favor of those that can handle extreme heat, a process that might also jeopardize the qualities that make vulnerable crops commercially desirable.

“We’re trying to figure out thermoregulation at a molecular and cellular level, and identify what and where we need to improve so that we can target those in commercial plant cultivars and conserve everything about them except for this one aspect that makes them vulnerable to extreme heat,” Ouonkap said. “Over time, you can start accumulating different resistance mechanisms as the growing conditions continue to change.”

Understanding thermotolerance, or the ability of a plant to withstand extreme temperatures, is a promising strategy to address climate adaptation, said study author Mark Johnson, a professor of biology at Brown.

“Imagine if you could just make a Heinz tomato more resilient to temperature stress without affecting the flavor profile or the way people experience the tomato,” Johnson said. “That would be a great advantage.”

Plant reproduction: a ripe area for research

The plant reproduction phase has been the focus of research in Johnson’s lab for many years. While the scientific literature includes studies of how heat stress affects plant growth in general, or the development of key reproductive structures, there was an absence of work that specifically examined what happens after pollen lands on the stigma during plant reproduction, Johnson said.

For Ouonkap’s thesis project, he focused on the pollen tube growth phase of the plant reproductive cycle. He studied different cultivars of tomato plants known for their ability to produce fruit in exceptionally hot growing seasons. The tomato varieties in the study were native to the Philippines, Russia and Mexico and were all grown in the Plant Environment Center at Brown.

Collaborating with scientists at the University of Arizona, Ouonkap studied how heat stress affects the ability of the pollen to grow in the flower of the tomato plant. He focused on how gene expression changes when tomato pollen produced by plants growing in optimal greenhouse conditions were exposed to high temperatures when growing in a petri dish.

The team’s partners in Arizona found that exposure to high temperature solely during the pollen tube growth phase limits fruit and seed production more significantly in tomato cultivars that were heat sensitive than those that were heat tolerant. Importantly, Ouonkap found that pollen tubes from the Tamaulipas variety of tomato, known to be tolerant to heat, have enhanced growth under high temperature. His molecular analysis of the pollen tube in these tomatoes allowed the research team to pinpoint the mechanisms that were associated with thermotolerance.

Tomatoes are an ideal organism for this kind of research, the researchers said. The ability of different varieties to adapt to a variety of extreme climates offer scientists insights into how species vary in their responses to environmental conditions. Tomatoes are also an important commercial crop in countries all over the world, from the Mediterranean to Egypt to Turkey to California — some of which are among the most vulnerable to extreme heat conditions.

With the right molecular mechanisms now identified, a next step would be determining specific techniques for enabling tomato growth in different climates. In one hypothetical scenario, scientists might develop a small molecule that could prime the pollen in the plants to be able to withstand a heat wave, Johnson explained.

“When the weather forecast showed two weeks of high temperatures during the pollen tube growth phase, the farmer would apply a product to plants that would change the gene expression so that the pollen would be resilient to heat,” he said.

While that type of manipulation is still far off in the future, the researchers said this area of research is ripe for exploration.

This project was funded by the National Science Foundation (IOS-1939255) with additional support from the United States Department of Agriculture National Institute of Food and Agriculture (2020-67013-30907, 2024-67012-41882) and the National institutes of Health (5R35GM139609, PI AEL).

Scientists from the University of East Anglia (UEA) say the study — the result of their autonomous Seaglider getting accidentally stuck underneath the Ross Ice Shelf — suggests this will likely only increase further as climate change drives continued ocean warming.

The glider, named Marlin, was deployed in December 2022 into the Ross Sea from the edge of the sea ice. Carrying a range of sensors to collect data on ocean processes that are important for climate, it was programmed to travel northward into open water.

However, Marlin was caught in a southward-flowing current and pulled into the ice shelf cavity where it remained, with its sensors on, for four days before re-emerging. During this time the ‘lost’ glider completed 79 dives, taking measurements of the water within the cavity to a depth of 200 metres, right up to base of the overlying ice shelf.

Researchers from UEA’s School of Environmental Sciences recorded a 50 metre-thick ‘intrusion’ of — relatively — warm water that had entered the cavity from the nearby open water. Water temperatures ranged from -1.9°C to a warmer -1.7°C under the ice.

Subsequent re-analysis of all available measurements shows that heat transported into cavity has increased over the last 45 years, most likely due to warming of the Ross Sea because of climate change. The findings are published in the journal Science Advances.

“While the temperature increase — four thousandths of a degree a year — might not seem all that much, it could lead to around 20 to 80 cm of additional ice loss per year over the 45 years we look at,” explained lead author Dr Peter Sheehan.

“We found the waters of the intrusion were warm enough to melt the underside of the ice shelf, unlike the freezing-point waters they likely displaced. What’s new here is that we can track the warm water pretty much from the open water of the Ross Sea at the ice front, back into the cavity. We have not seen one of these intrusions happening directly before.”

Dr Sheehan added: “A trip into the cavity underneath the Ross Ice Shelf was not planned, and it’s not normally possible to measure this region of an ice shelf: you can’t send instruments this close to the underside of an ice shelf deliberately, it’s too risky.”

The ice shelves that surround Antarctica are exposed to the warmth of the ocean across the expanse of their undersides that float out over the continent’s shelf seas, and the ocean-driven melting that occurs at the ice base is the largest cause of Antarctic ice-mass loss.

While the melting of floating ice does not itself substantially raise sea level, ice shelves slow the seaward flow of land ice and so stabilize the Antarctic ice sheet; their thinning and disintegration would hasten the delivery of land ice to the ocean and accelerate global sea-level rise.

One of the processes that can drive warm surface water under the Ross Ice Shelf is wind. Certain wind patterns lead to southward flow in the surface ocean and into the ice shelf cavity.

These wind-driven ocean-surface flows are called Ekman currents, and as with any ocean current, these have an associated heat transport. Because this is an ocean-surface process, this heat is instantly available to melt the overlying ice: it doesn’t have to wait to be mixed upward to the ice base.

Ekman heat transport is particularly relevant for climate scientists because oceans absorb and redistribute much of the Earth’s heat. Changes in this system can have profound effects on weather, sea levels, and global temperature trends.

Dr Sheehan and co-author Prof Karen Heywood used long-term measurements of wind and ocean temperature — blended with a model to fill in spatial and temporal gaps in the record — to calculate the strength of southward Ekman heat transport over the last 45 years. They found that the heat transported into the cavity by Ekman currents has increased.

Year-to-year variability is driven by the wind. However, the trend towards greater heat transport into the cavity is likely linked to warming of the Ross Sea — because the water has warmed, winds today will transport more heat energy into the cavity than winds of comparable strength in the past.

Prof Heywood said: “It appears reasonable to expect that the magnitude of the Ekman heat flux, and of the melting that it drives, will increase yet further as climate change drives continued ocean warming. This trend is a concern in itself.

“The influence of surface-water intrusions, alongside the trends and variability in the Ekman dynamics that can drive these, must be incorporated into climate models, not least given continued uncertainty in the response of Antarctic land-based ice to climate change.”

This is the first time that this process has been looked at using a long-term, multi-decadal data set. Previous understanding of surface-water intrusions has come mainly from comparisons of hydrography in open water, for example from ships, observations from tagged seals, and ice moorings deployed within a cavity.

The study was funded by the UK Natural Environment Research Council, the US National Science Foundation and European Research Council Horizon 2020 programme.

The legendary scientist, who lived from 1906-1984, studied and documented the stratigraphy and sedimentation of Colorado Plateau geology, especially the Grand Canyon’s Cambrian Tonto Group, for more than 50 years. His time-tested tenets have influenced generations of geoscientists.

“The Tonto Group holds a treasure trove of sedimentary layers and fossils chronicling the Cambrian Explosion some 540 million years ago, when the first vertebrates and animals with hard shells rapidly proliferated and sea levels rose to envelope continents with emerging marine life,” says Carol Dehler, professor at Utah State University. “McKee marveled at this pivotal geologic period, yet had no knowledge of plate tectonics or global sea level change, and his ideas were often shunned by the scientific community of the time.”

Yet, what if McKee could have fast-forwarded through time and availed himself of current-day stratigraphic, depositional and paleontological models, data and technological muscle?

Dehler, with colleagues James Hagadorn of the Denver Museum of Nature & Science, Frederick Sundberg, Karl Karlstrom and Laura Crossey of the University of New Mexico, Mark Schmitz of Boise State University and Stephen Rowland of the University of Nevada, Las Vegas, along with their students and interns, have employed these tools to construct an updated and insightful framework of McKee’s foundational ideas. They report their efforts in “The Cambrian of the Grand Canyon: Refinement of a Classic Stratigraphic Model,” the cover story of the November 2024 print issue of the Geological Society of America’s GSA Today journal, published online Oct. 23, 2024.

The team’s research was supported by a National Science Foundation Division of Earth Sciences grant.

“The Grand Canyon is an epic Rosetta Stone for geology,” says Hagadorn, Tim & Kathryn Ryan Curator of Geology at DMNS. “And we’re helping to further decode it. Because Grand Canyon rocks record global changes in climate and tectonics, our work help us understand strata that were deposited worldwide during the Cambrian period.”

Studying the Tonto Group, he says, is like being a detective at a crime scene.

“You can see clues and discern at least part of what happened,” Hagadorn says. “But determining how it happened and the sequence of events takes time and effort. Just like the scene of a crime, the rock record of the Grand Canyon is much more complicated than what we currently know and its story is still being written.”

Dehler says the team’s new model offers three key pathways for deeper understanding.

“From the Tonto Group’s 500-meter-thick strata, we’re learning about sea-level rise and the effects of catastrophic tropical storms — probably more powerful than today’s devastating hurricanes — during a period of very hot temperatures when the Earth was ice-free,” she says.

Sea levels were so high during this time period, Dehler says, that rocks like the Tonto Group were deposited atop every continent on Earth, as seas bathed the continents in a complex mosaic of shallow marine, coastal and terrestrial environments.

Further, she says, advanced chronological tools are revealing new information about the tempo of sedimentation, as well as how rapidly trilobites and other “disgusting, cockroach-looking creatures” diversified.

“Our findings are a reminder science is a process,” Hagadorn says. “Our work in the Grand Canyon, one of the world’s most well-known and beloved landscapes, connects people to this science in a very personal way.”