An experiment makes lagoon waves pink, here's how

The remaining releases are scheduled for late January and early February 2023, with the first three dye releases starting on January 20.

"We performed our first dye release at Los Peñasquitos Lagoon on Friday, January 20, 2023, with much success. We began the release at 9 am, just inside the mouth of the river. The morning presented larger waves than we expected, and the initial plume outflow demonstrated trapping in the surf zone", said the researchers.

Little is understood so far

Fresh water and materials, such as sediments and pollutants, are vital for getting to the coastal ocean through rivers and estuaries. However, little is understood about the interactions between these plumes of lighter, fresher water and the denser, saltier, and frequently colder nearshore ocean environment, mainly when the plumes come into contact with breaking waves.

"I'm excited because this research hasn't been done before and it's a really unique experiment," said Scripps coastal oceanographer Sarah Giddings, who is leading the PiNC study.

"We're bringing together a lot of different people with different expertise, such that I think it's going to have some really great results and impacts. We will combine results from this experiment with an older field study and computer models that will allow us to make progress on understanding how these plumes spread."

Giddings pointed out that while there has been little research on smaller-scale freshwater plumes that interact with the surf zone, many prior oceanographic studies have concentrated on large-scale freshwater plumes with substantial output. Because it is a "great example" of a tiny river plume discharging into the surf zone over a generally consistent stretch of shoreline, the Los Peasquitos Lagoon was selected as the study location. The lagoon is a tiny estuary that is occasionally closed and is tucked between the towns of San Diego and Del Mar.

"Los Peñasquitos Lagoon is a very dynamic system, with different elements changing each day, often even over the course of one day," said Scripps postdoctoral scholar Alex Simpson

"I am looking forward to seeing how the balance of physical forces—ocean waves competing against river outflow—determine the fate of the estuary water as it enters the coastal ocean on the days that we conduct our field experiment. I'm also very excited to fly a new type of drone system with a camera that has nearly 100 times the capability to distinguish the visible light spectrum than our phone camera," Simpson added.