By Studying Polar Ice Sheets, David Holland Seeks to Predict Rising Sea Levels

David Holland, Courant Institute Mathematics Professor and past Director of Courant’s Center for Atmosphere Ocean Science (CAOS), recently returned from two months spent installing ice measurement instrumentation, observing melting ice flows and collecting data from the frozen fjords of Greenland and Antarctica in hopes that scientists, today and in generations to come, will be able to predict the rate at which sea levels are rising.

Rising global sea level is one of the most pressing issues currently being studied by the CAOS group – specifically, “why it is changing and how much might it change in the next hundred years or so,” explains Professor Holland. “To try to determine that, we look at two huge ice sheets, one in Greenland and the other in Antarctica. When this ice melts and flows into the ocean, it causes the sea level to rise, but not just in one place. Similar to an ice cube being put into and then melting in a glass of water, when marine ice melts, the sea level rises everywhere, really fast,” he says.

Holland’s group of researchers is studying not only the thickness of the ice but also the movement of water flowing out to the ocean and back in to land again. For millions of years, melted ice has been traveling to the ocean by way of canal-like passageways, or fjords, Holland says. “When warm water from the ocean flows through the fjords to the ice-covered land, this causes the ice to melt and come back out. Our goal is to place a temperature sensor into the ocean so we can see whether or not warm water is coming into the fjords and ice is flowing out, which is the issue affecting global sea level change for this century and the next.”

Surprisingly, even with today’s technology, instrumentation, and data analysis capabilities, Holland says that scientists cannot predict future sea levels because the mathematical and physical constructions to simulate what will happen to the Greenland ice sheet, and far more importantly, the larger Antarctica one, do not exist.

“We have mathematical tools, numerical methods and computers,” Holland explains. “But when you attempt to write your equation down, you realize you don’t know what to write because you haven’t studied the details of what you’re trying to describe. That’s why for the last five years, I’ve done field observation, collecting data that will hopefully bring some insight into what we’re trying to describe.”

Collecting this data will take at least 100 years, Holland predicts. “Generations will be doing this. We’re just trying to make moderate progress and meaningful contributions, so that future researchers will find our data set really useful, and can then go off and develop some theory based on it.”

NYU’s Center for Data Science is well-timed, Holland notes, coinciding with the data his group is collecting. “There are vast amounts of data coming from satellites flying over the ice sheets daily, generating vast data sets over decades,” he says. “The ability to sift through this requires data science. This is becoming so important and sophisticated, and it’s allowing us to learn amazing things,” he adds. “I can see only more of it coming.”

By M.L. Ball