The Forest Through the Fog

By Annaliese Hettinger

The atmosphere within Northern California’s coast redwood forests is humid, the air pungent and loamy, smelling at once like the sea and earth. This olfactory fusion is appropriate; scientists have discovered that redwood forests thrive on a sea-sourced fog that carries nutrient-rich coastal ocean water. However, uncovering the numerous processes that make it possible for the sea to nourish the trees requires novel approaches and multiple disciplines to uncover.

Thanks to a new National Science Foundation (NSF) grant, researchers from seven institutions, including Oregon State University, have formed an interdisciplinary team to study the relationships among upwelling, fog, coast redwood forests and climate change. The Summen Project, named after the indigenous Ohlone word for “redwood,” was awarded $1.75 million over three years through the NSF’s Coastal Science, Engineering and Education for Sustainability program. The project aims to unravel the complex ocean-atmosphere-land interactions supporting one of the Earth’s most productive and alluring terrestrial ecosystems and make predictions about how climate change may alter them.

Coastal fog is generated by warm, high-pressure air mixing with cold ocean water brought to the sea surface through upwelling. Upwelling originates when winds blowing from the north drive surface waters west, pushing them offshore. Deeper, colder water then rises from below to take the place of the surface water. Upwelling occurs along our coastline beginning in spring and lasting into early fall, but there are indications that the timing and intensity of this process may be in flux because of changing land and ocean surface temperatures.

Scientists understand the importance of coastal upwelling within marine ecosystems. The cold, nutrient-rich waters pulled to the sea surface support phytoplankton species that form blooms and feed some of the most productive fisheries globally. Less understood is how upwelling supports coastal redwood forests. Coastal fog drawn into redwood forests bears vital moisture, but also nitrogen, phosphorus and minerals picked up from ocean waters during upwelling. In this way, the sea nourishes the giants of our coastal terrestrial ecosystems through the presence of fog, but models describing how that happens are difficult to build.

“Predicting the extent of fog formation is a complex and delicate task, and one of the most difficult parameters to get right in computer simulations of the atmosphere,” explains Eric Skyllingstad, professor of atmospheric sciences at Oregon State University and part of the Summen Project.

Complicating matters even more is that fog appears to be sensitive to a changing climate. Redwood trees rely on moisture from fog during the dry summer. Yet coastal fog declined over the last half-century, and scientists suspect it may be connected in some way to changes in the upwelling season. Until recently, atmospheric models were unable to simulate coastal fog, making it difficult to predict how climate change could modify these ocean-atmosphere-land interactions.

Roger Samelson, a CEOAS researcher and part of the Summen Project, says that the tangled relationship between the ocean and atmosphere is precisely why he and CEOAS colleagues Eric Skyllingstad and Simon de Szoeke were brought on board.

“We are one of the few groups looking at the coupled ocean-atmosphere system in an upwelling context,” explains Samelson.

The Summen Project has an ambitious goal – to understand how ocean-atmosphere-land interactions, mediated by coastal fog, help to feed some of the tallest trees on the planet. Revealing this relationship will most certainly take this interdisciplinary team of experts on an epic journey, from hundreds of feet above the sea to beneath the ocean waves, with fog floating between.