Author Archives: klaseks

Ocean basins are like trumpets– no, really.

We’re all familiar with waves when we go to the coast and see them wash onto the beach. But since ocean waters are usually stratified by density, with warmer fresher waters on top of colder, saltier ones, waves can occur between water layers of different densities at depths up to hundreds of meters. These are called internal waves. They often have frequencies that are synched with the tides and can be pretty big–up to 200 meters in amplitude! Because of their immense size, these waves help transfer heat and nutrients from deep waters, meaning they have an impact on ocean current circulation and the growth of phytoplankton.

The line of foam on the surface of the ocean indicates the presence of an internal wave.

We still don’t understand a lot about how these waves work. Jenny Thomas is a PhD student working with Jim Lerczak in Physical Oceanography in CEOAS (OSU’s College of Earth, Ocean, and Atmospheric Sciences). Jenny studies the behavior of internal waves whose frequencies correspond with the tides (called internal tides) in ocean basins. This requires a bit of mathematical theory about how waves work, and some modeling of the dimensions of the basin and how it could affect the height of tides onshore.

Picture a bathtub with water in it. Say you push it back and forth at a certain rate until all the water sloshes up on one side while the water is low on the other side. In physics terms, you have pushed the water in the bathtub at one of its resonant frequencies to make all of it behave as a single wave. This is called being in a normal mode of motion. Jenny’s work on the normal modes of ocean basins suggests that the length-to-width ratio and the bathymetry of an ocean basin influence the structure of internal tides along the coast. Basically, if the tidal forcing and the shape of the basin coincide just right, they can excite a normal mode. The internal wave can then act like water in a bathtub sloshing up the side, pushing up on the lower-density water above it.

It turns out that water isn’t the only thing that can have normal modes. The air column in a wind instrument is another example. Jenny grew up a child of two musicians and earned a degree in trumpet performance from the University of Iowa, and she occasionally uses her trumpet to demonstrate the concept of normal modes. She can change pitches by buzzing her lips at different resonant frequencies of the trumpet–the pitch is not just controlled by the valves.

Jenny uses her trumpet to explain normal modes.

Near the end of her undergraduate degree at the University of Iowa, Jenny discovered that she had a condition called fibrous dysplasia that could potentially cause her mouth to become paralyzed. Deciding a career as a musician would be too risky, and realizing her aptitude for math and physics, she went back to school and earned a second undergraduate degree in physical oceanography at Old Dominion University. After a summer internship at Woods Hole Oceanographic Institution conducting fieldwork for the US Geological Survey, she decided to pursue a graduate degree at OSU to further examine the behavior of internal waves.

Tune in to 88.7 KBVR Corvallis to hear more about Jenny’s research and background (with a trumpet demo!) or stream the show live right here.

Jenny helps prepare an instrument that will be lowered into the water to determine the density of ocean layers.

Jenny isn’t fishing. The instrument she is deploying is called a CTD for Conductivity, Temperature, and Depth–the three things it measures when in the water.

The Breathing Seafloor

In the cold, dark depths of the seafloor across the world, microbes living in sediments and on rocks are quietly breaking down organic material and sucking dissolved oxygen out of the seawater. The continental shelf off of Oregon’s coasts, home to a fishing industry that brings in over a hundred million dollars of revenue per year, is no exception. Does oxygen consumption, and therefore carbon cycling, vary by location, or across seasons? Setting a baseline to investigate these patterns of oxygen drawdown is crucial to understanding habitats and distributions of fish stocks, but will also establish what “normal” oxygen consumption looks like off our shores. Measurements like these are also used by the Intergovernmental Panel on Climate Change (IPCC) to estimate global patterns of carbon burial. If any forces were to shift these patterns in the future, we’d at least have a baseline to allow us to diagnose any “abnormal” conditions.

Peter Chace is a third-year PhD student of Ocean Ecology and Biogeochemistry in the College of Earth, Ocean, and Atmospheric Sciences (CEOAS). Peter’s research focuses on developing a technique of measuring fluxes of oxygen across the seafloor called Eddy covariance. This technique takes high-resolution time measurements of three-dimensional velocities of water moving in turbulent whorls, or random circular patterns, within the boundary layer of a fluid like air or water. Eddy covariance has been employed to measure fluxes across air layers on land for decades, but has only recently been applied in marine systems. A point-source oxygen measurement within this turbulent layer is measured with a microelectrode and combined with the velocity data to develop a flux. Why go through all this trouble? Other ways to measure oxygen fluxes, like putting chambers over an area of seafloor and waiting to measure an oxygen drawdown, require a lot of work and give little temporal resolution.

Workers on the RV Oceanus, Oregon State’s largest research vessel, deploy a benthic (seafloor) oxygen sensor.

Peter can calibrate his microelectrodes to measure other chemicals and obtain their fluxes across the seabed, but he is mainly focused on oxygen. To measure fluxes off the Oregon coast, Pete and his advisor, Dr. Clare Reimers, will head to sea on the RV Oceanus several times this fall and winter to deploy their sensor on the seafloor for days at a time. The desk-sized seafloor lander and the microelectrode attached to it are fragile, and the rough seas offshore Oregon in fall and winter will make it a challenging endeavor. We hope they pack enough seasickness medication and barf bags!

You get right up close and personal with the ocean when you send down these instruments… and this is on a clear day with calm seas!

Since growing up as a child in New Jersey, Peter has always wanted to learn about the ocean. While studying chemistry and marine biology at Monmouth University (in New Jersey) as an undergraduate, he completed a summer REU (Research Experience as an Undergraduate) with his current advisor, Clare Reimers, here at Oregon State University. He also interned for NOAA (the National Oceanic and Atmospheric Association), analyzing the chemistry of hydrothermal vent fluids with Dr. David Butterfield. Pete revisited a hydrothermal system on a cruise to the East Pacific Rise off of Central America where he got a remarkable opportunity to dive in Alvin, the submersible that discovered the wreckage of the Titanic.

Here’s Pete in the submersible Alvin just before the dive, checking his microelectrodes.

To hear more about Peter’s research on sensor development and his seafaring expeditions, tune in to Inspiration Dissemination on Sunday, October 15th at 7pm on 88.7 KBVR Corvallis. Or stream it online here!

Characterizing off-channel habitats in the Willamette River: Fish need to cool off too!

During the summer, when the mercury clears triple digits on the Fahrenheit scale, people seek out cooler spaces. Shaded parks, air conditioned ice cream parlors, and community pools are often top places to beat the heat. If you’re a resident of Corvallis, Oregon, you may head downtown to dip your toes in the Willamette River. Yet while the river offers a break from the hot temperatures for us, it is much too warm for the cold water fishes that call it home.

Where do fish go to cool off?

As a master’s student in the Water Resources Graduate Program at Oregon State University, Carolyn Gombert is working to understand where cold water habitat is located along the Willamette River. More importantly, she is seeking to understand the riverine and geomorphic processes responsible for creating the fishes’ version of our air conditioned ice cream parlors. By placing waterproof temperature loggers along sites in the upper Willamette, she hopes to shed light both on the temporal and spatial distribution of cold water patches, as well as the creation mechanisms behind such habitats.

 

The cart before the horse: seeking to reconcile science and policy

Because the Willamette Basin is home to Cutthroat trout and Chinook salmon, the river is subject to the temperature standard adopted by the state of Oregon in 2003. Between May through October, Cutthroat and Chinook require water cooler than 18 degrees Celsius (64.4 degrees Fahrenheit). Currently, the main channel of the Willamette regularly exceeds this threshold. The coolest water during this time is found in side channels or alcoves off the main stem. While Oregon law recognizes the benefits these “cold water refuges” can provide, our scientific understanding of how these features change over time is still in its early stages.

Emerging stories

Data collection for Carolyn’s project is slated to wrap up during September of 2017. However, preliminary results from temperature monitoring efforts suggest the subsurface flow of river water through gravel and sediment plays a critical role in determining water temperature. By pairing results from summer field work with historical data such as air photos and laser-based mapping techniques (LiDAR) like in the image below, it will be possible to link geomorphic change on the Willamette to its current temperature distributions.

Between 1994 and 2000, the Willamette River near Harrisburg, Oregon shifted from a path along the left bank to one along the right bank. This avulsion would have happened during a high flow event, likely the 1996 flood.

No stranger to narratives

Prior to beginning her work in hydrology at OSU, Carolyn earned a bachelor’s in English and taught reading at the middle school level. Her undergraduate work in creative writing neither taught her how to convert temperature units from Fahrenheit to Celsius nor how to maneuver in a canoe. But the time she spent crafting stories did show her that characters are not to be forced into a plot, much like data is not to be forced into a pre-meditated conclusion. Being fortunate enough to work with Stephen Lancaster as a primary advisor, Carolyn looks forward to exploring the subtleties that surface from the summer’s data.

If you’d like to hear more about the results from Carolyn’s work, she will be at the OSU Hydrophiles’ Pacific Northwest Water Research Symposium, April 23-24, 2018. Feel free to check out past Symposiums here. Additionally, to hear more about Carolyn’s journey through graduate school, you can listen to her interview on the Happie Heads podcast.

Carolyn conducting field work on the Willamette.

Carolyn Gombert wrote the bulk of this post, with a few edits contributed by ID hosts.