Allie, Kyle, Jesse, Ron, Melissa, Alysia and me. Sampling water from the Niskin bottles after a CTD cast into upwelled waters along the Oregon coast. Above, Patrick drives the line that lowers the bottles down to a 100 meters and reminds us to wear safety vests. Photo credit: Frank Gonzalez
Yesterday ended our drifter journey following upwelled water, and it is refreshing now to have finally experienced 6 hours of sleep without interruption. The three day blur included a 2-day shift of waking up every 4 fours to take a surface water sample. Many thanks to Steve from the crew for cookies and snacks during this time.
Outside the wake-up-every-4-hours period, the whole science party also participated in CTD (conductivity, temperature, depth) deployments every 6 hours. My continuous, second-by-second optical measurements and those samples I took every 4 hours for Nina will resolve the surface ocean layer very, very well. The data fill in a rich, 2-dimensional picture of the water our ship has meandered through, and how it may have evolved in the last three days. CTD deployments, by contrast, illuminate a third dimension. With each one, we cast water collection bottles and instruments that measure temperature and seawater optical properties down to a few hundred meters below surface.
Some immediate data that these CTD casts offer is the structure of the water “column” below our continuous surface measurements. Because the ocean has three dimensions, these vertical data help us understand our surface measurements as part of a greater volume of seawater rather than just a slice. Light profiles, for instance, tell us how deep sunlight penetrates this “column”, giving us an idea of how deep photosynthesizing algae can persist. Fluorescence profiles allude to concentrations of the algal pigment chlorophyll at each depth, sometimes revealing the famous “deep chlorophyll maximum”, which results from algae adapting to deeper, darker waters by packing more chlorophyll into their cells. The extra chlorophyll boost in their cells helps them harvest more light to continue photosynthesis at such depths.
From drifter round #1, we have grown wiser to the challenges of observing upwelling. Our drifter was no more than four orange Styrofoam balls, a GPS locator, and a submerged net that fanned out into the upwelled water mass. So, one purely logistical challenge was steering behind the windy path that this water pulled the drifter; R/V Oceanus could never stray too far if we wanted to be sure that were analyzing the right seawater. Moreover, while we shifted directions, we were certainly not alone. The ship’s steering crew were very busy alerting nearby fishing vessels not to run over our drifter device.
Today, we dropped drifter #2 into a new water mass, and this time the water we track is not upwelling water. But, it is another unique packet of water that differs from its surrounding waters. It has many fewer algae living in it that the water we tracked with drifter #1. It will be our natural, “controlled” laboratory for the rest of our cruise at sea, and hopefully it will allow us one more rare glimpse of how ocean life and conditions change day to day.