Student Spotlight: Research on seafloor has great implications for sea levels

Ken Zhao, a PhD candidate in UCLA’s Department of Atmospheric and Oceanic Sciences (AOS), published phenomenal research on seafloor effects on melting glaciers. In collaboration with AOS faculty members Andrew Stewart and Jim McWilliams, Zhao’s research focuses on the Pine Island Glacier in West Antarctica and Jakobshavn Glacier in West Greenland, two of the fastest melting glaciers in their

Pine Island Glacier

A satellite image of the Pine Island Glacier dated October 25, 2018. The newest iceberg to fall off is three times the area of Manhattan.

respective regions. Both of these glaciers have tall bathymetric sills – essentially, a bump on seafloor around the glacier. The research by Zhao, Stewart, and McWilliams seeks to understand how the height of the bump holds back the open ocean’s warm water from melting the glaciers in these regions.

Zhao has always enjoyed the “thrill of solving math problems and conducting scientific experiments.” This research became one of those thrills with a much larger effect: helping society.

Nearly all of humanity will be affected by sea level rise in the coming decades. The most uncertainty with this sea level rise stems from the ice sheets and glaciers in Antarctica and Greenland.

“We have realized quite recently that warm ocean water is melting the margins of these ice sheets from below much faster than the atmosphere is melting it from above,” Zhao said.

Many of these glaciers are holding back reservoirs of inland ice. Thus, if the glacier melts or comes crashing down, there would be a huge increase in sea level height. To accurately predict sea level rise in the future, we must study how the ocean drives the melting of glaciers in these vulnerable areas and how the rate of warm water inflow is controlled by certain factors such as bumps in the seafloor.

Glacier Model

Zhao’s idealized geometry, with a two-layer model, based on the Pine Island Glacier.

Zhao’s research is the first of its type to explore how the height of the sills on the ocean floor can control the inflow of warm water that is driving most of the melting. The research strips down the modeling to a simplified scenario to explore a large enough set of parameters that will be relevant to most glaciers. From these models have come comprehensive theories to predict how high the transport of in-flowing warm waters is over the relevant parameters.

This is not the only first that has come out of Zhao’s research.

“[We] discovered the existence of a few new fluid phenomena that have not yet been observed in real shelf cavities,” he explained. Although his research does not focus on these specific areas, he hopes that it will motivate future field work to observe such phenomena because they could have direct impact on the melting of some of the most vulnerable glaciers.

Zhao’s published research on the Pine Island and Jakobshavn glaciers focuses on how glaciers melt, but that has great implications for the science and technology around stopping rising sea levels, and hopefully mitigating damage to our planet. It is likely that within this lifetime there will be a need to resort to geo-engineering as a measure to delay the effects of climate change and sea level rise.

“In particular, building sea walls around the periphery of New York City are currently being considered as a real future possibility by the US Army Corps. of Engineers,” Zhao said. However, Zhao’s current research expresses that it would be more effective slow down sea level rise at its source by increasing the height of the sills on the seafloor to stop the inflow of warm water toward melting glaciers. Although not all of the information necessary to understand the effects and implications for such a project are at hand, it may be a possibility for the future.

Complex Glacier Model

Model of a 3D domain of open ocean outside of Jakobshavn Glacier, exhibiting more geometric complexity.

The next step is considering all of the complex interactions that take place in a larger, realistic model of the real ocean. Zhao, McWilliams, and Stewart now work to understand how the complexities of the geometry of side slopes of sills, bays, and multiple sills will influence and control the transport of warm water from the open ocean to the glaciers. This will help better the understanding of the supply pathways of heat that are necessary to melt the margins of the ice sheets.

It’s the thrill of science that motivates Zhao to further his understanding of these ocean floor effects. He explains why by quoting his adviser, Jim McWilliams: “Mathematics is fun, but science has real targets.” Zhao added, “Polar oceanography and cryosphere science are even more fun and real because the targets and results will likely influence all of us during our lifetime.”

Zhao, McWilliams, and Stewart research may have great impacts on the future of science and technology around glacial melting, and ultimately bringing sea level rising to a necessary stop.

Zhao’s research is published in the Journal of Physical Oceanography (an American Meterological Society Journal). Click here to read.
Photo credit: Ken Zhao/Landsat OLI imagery processed by Stef Lhermitte, Delft University of Technology.