NASA’s SARP West 2024: Oceans Group Exploration

Faculty Advisor: Dr. Henry Houskeeper, Woods Hole Oceanographic Institute

Graduate Mentor: Lori Berberian, University of California, Los Angeles

Lori Berberian, the graduate student mentor for the 2024 SARP West Oceans group, introduces each group member and shares behind-the-scenes insights from the internship.

Emory Gaddis, Colgate University

Coal Oil Point, located in the Santa Barbara Channel of California, is one of the world’s largest hydrocarbon seep fields. The area has sustained both scientific interest and commercial activity for decades due to its natural hydrocarbon seepage and oil production. Indigenous peoples historically used the naturally occurring tar for waterproofing baskets, indicating the presence of hydrocarbons long before modern oil extraction started. Hydrocarbon seepage involves gaseous hydrocarbons being released from the marine floor through a process called seeping, where reservoir pressure builds up relative to hydrostatic pressure, causing bubbles, oily bubbles, and droplets to rise to the surface. This seepage is a significant source of methane (CH4), a major greenhouse gas, into the atmosphere.

Current optical remote sensing techniques for detecting oil in the ocean leverage various factors such as changes in sun glint, sea surface damping, and wind roughening due to varying oil concentrations. We use high-resolution (3m) surface reflectance observations from PlanetScope to create a time series of oil slick surface areas from 2017 to 2023 within the Coal Oil Point seep field. Our initial methods involve manual annotations in ArcGIS-Pro. We assess potential relationships between wind speed and oil slick surface area, which helps us correct for factors that modify oil slick surface area and test for changes in natural seepage rates. This can determine whether human activities like oil drilling alter natural oil seepage. Future investigations into oil slick chemical properties and the impact of natural seepage on marine and atmospheric environments can help optimize oil extraction locations.

Rachel Emery, The University of Oklahoma

The world is currently facing an unprecedented biodiversity crisis, with high biodiversity areas at the greatest risk of species extinction. One such hotspot is the Western Cape Province of South Africa, which features a unique marine ecosystem due to the extensive growth of canopy-forming kelps like Macrocystis and Ecklonia. These kelps provide three-dimensional structures that foster biodiversity and productivity. However, they face increasing threats from marine heatwaves and pollution related to climate change and local water quality issues.

Traditional field surveying methods can monitor these ecosystems, but remote sensing via airborne and satellite observations offers improved spatial coverage and resample rates, along with extensive historical continuity for tracking changes over multiple decades. Passive remote sensing observations, like those from NASA’s Airborne Visible-Infrared Imaging Spectrometer – Next Generation (AVIRIS-NG), provide high-resolution, hyperspectral imagery of oceanic environments. These observations can help characterize community dynamics and quantify physiological changes in macroalgae.

Active remote sensing methods, such as Light Detection and Ranging (LiDAR), are less understood in marine ecosystems but are anticipated to offer novel observations of vertical structures not supported by passive sensing. We investigate the potential to observe emergent canopy-forming macroalgae, like Ecklonia, using NASA’s Land, Vegetation, and Ice Sensor (LVIS), which offers decimeter-scale vertical resolution. We validate LVIS observations using data from AVIRIS-NG imagery to see if LiDAR remote sensing can improve monitoring of emergent kelps in key biodiversity regions like the Western Cape.

Brayden Lipscomb, West Virginia University

Understanding the optical properties of marine ecosystems is crucial for improving models related to oceanic productivity. Models that relate satellite observations to oceanic productivity or subsurface light availability often face uncertainties when parameterizing vertical structures and deriving columnar parameters from surface observations. The most accurate models use in situ data, minimizing assumptions like atmospheric optical thickness or water column structure.

For instance, satellite primary productivity models have shown improved accuracy by incorporating vertical structure information from gliders and floats. We analyze vertical profiles in photosynthetically available radiation (PAR) obtained during routine surveys of the southern California Current system by the California Cooperative Oceanic Fisheries Investigation (CalCOFI). We find that depths of 1% and 10% light availability show coherent log-linear relationships with attenuation measured near the surface, despite vertical variability in water column constituent concentrations and instrumentation challenges related to sensitivity, self-shading, and ship adjacency. Our results suggest that subsurface optical properties can be more reliably parameterized from near-surface measurements than previously understood.

Dominic Bentley, Pennsylvania State University

Upwelling is the rise of the nutricline, thermocline, and isopycnals due to the advection by eddies of the surface ocean layer. This effect increases the productivity of algal blooms in a given body of water. Mesoscale to deformation scale eddy circulation modulates productivity based on factors like latitude, season, and direction. However, many processes governing the effects of eddies on the ocean microbial environment remain unknown due to limitations in observations linking eddy strength and direction with productivity and ocean biogeochemistry.

Satellites currently provide the only ocean observing system that allows for broad spatial coverage with high resample rates, although they face limitations due to cloud obstructions and being limited to near-surface observations. A persisting knowledge gap in oceanography stems from the spatial resolution limitations of observations resolving submesoscale dynamics. The recent launch of the Surface Water and Ocean Topography (SWOT) mission in December 2022 supports observations of upper-ocean circulation with increased resolution relative to legacy missions. Meanwhile, the launch of the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite in February 2024 is anticipated to improve knowledge of ocean microbial ecosystem dynamics.

We match up SWOT observations of sea surface height (SSH) anomalies, which are informative about eddy vorticity, with PACE observations of surface phytoplankton biomass and community composition. This helps us relate the distribution of phytoplankton biomass and assemblage structure to oceanic eddies in the North Atlantic. We observe higher concentrations of Chlorophyll a (Chla) within SSH minima, indicating the stimulation of phytoplankton productivity by cyclonic features associated with upwelling-driven nutrient inputs.

Abigail Heiser, University of Wisconsin-Madison

In 1905, flooding from the Colorado River gave rise to what would become California’s largest lake, the Salton Sea. Today, most of its inflow comes from agricultural runoff, which is rich in fertilizers and pollutants. This leads to elevated lake nutrient levels that fuel harmful algal blooms (HAB) events. Increasingly frequent HAB events pose ecological, environmental, economic, and health risks to the region by degrading water quality and introducing environmental toxins.

Using NASA’s Earth Surface Mineral Dust Source Investigation (EMIT) imaging spectrometer, we apply two hyperspectral aquatic remote sensing algorithms: the cyanobacteria index (CI) and scattering line height (SLH). These algorithms detect and characterize the spatiotemporal variability of cyanobacteria, a key HAB taxa. Originally designed to study atmospheric mineral dust, EMIT’s data products provide novel opportunities for detailed aquatic characterizations with both high spatial and high spectral resolution. Adding aquatic capabilities for EMIT would introduce a novel and cost-effective tool for monitoring and studying the drivers and timing of HAB onset, improving our understanding of environmental dynamics.

Emma Iacono, North Carolina State University

Over the past several decades, the world has witnessed a steady rise in average global temperatures, a clear indication of the escalating effects of climate change. In 1990, Andrew Bakun hypothesized that unequal warming of sea and land surface temperatures would increase pressure gradients, leading to rising rates of alongshore upwelling within Eastern Boundary Currents, including the California Current System (CCS). An anticipated increase in upwelling-favorable winds would have profound implications for the productivity of the CCS, where upwelled waters supply nutrient injections that sustain coastal ocean phytoplankton stocks.

Increasing upwelling is expected to increase the turbidity of the upper ocean, corresponding with greater phytoplankton concentrations. Historical observations of turbidity are supported by observations obtained using a Secchi Disk, an opaque white instrument lowered into the water column. Observations of Secchi depth, or the depth at which light reflected from the Secchi Disk is no longer visible from the surface, provide a quantification of light penetration into the euphotic zone. The shoaling, or shallowing, of Secchi disk depths was previously reported for inshore, transition, and offshore waters of the central and southern CCS for historical observations spanning 1969-2007.

Here, we reassess Secchi disk depths during the subsequent period spanning 2007 to 2021 and test for more recent changes in water clarity. Additionally, we evaluate the seasonality and spatial patterns of Secchi disk trends to test for potential changes to oceanic microbial ecology. Indications of long-term trends in some of the coastal domains assessed were found. Generally, our findings suggest a reversal of the trends previously reported. In particular, increases in water clarity, likely associated with a recent marine heatwave (MHW), may be responsible for recent changes in Secchi disk depth observations. This illustrates the importance of MHW events in modifying the CCS microbial ecosystem.

Click here to watch the Atmospheric Aerosols Group presentations.

Click here to watch the Terrestrial Ecology Group presentations.

Click here to watch the Whole Air Sampling (WAS) Group presentations.

For more Information, Refer to this article.