Ruthie Halberstadt, Glaciologist

 

Ruthie doing field work in the Dry Valleys, Antarctica, helping to collect a permafrost core that records ice sheet dynamics during the mid-Miocene (a very warm time period ~14 million years ago, the last time that atmospheric CO2 levels were similar to today).

What do you do, and how does your research contribute to the understanding of climate change?

I study ice sheet dynamics in Antarctica, which means that I am interested in the processes that influence how ice mass gets moved off the continent and into the ocean, in either solid (iceberg) or liquid form. The term ‘ice-sheet dynamics’ may be confusing if you think of Antarctica as a giant frozen ice cube. Instead, think of the Antarctic ice sheet as a giant cone of sand – when you pour dry sand on the top of a sand pile with steep edges, rivulets of sand start to form. These ‘streams’ move sand from the top of the pile out to the edges. In Antarctica, the same process (gravity) creates fast-moving corridors of ice – we even call them ‘ice streams’.

OK, so what about the ‘dynamics’ part? Now imagine that your pesky little sister takes a shovel, and removes a chunk of sand at the edge of the pile. Sand will flow into the newly-created hole, right? The same thing happens when warm ocean temperatures melt ice at the edges of the Antarctic continent: ice streams speed up and move more ice off the continent and into the ocean. Warm air temperatures can also increase surface meltwater production which can drain into crevasses and promote iceberg calving, also causing ice streams to drain more ice into the ocean.

These processes add to the total volume of water in the ocean. Therefore, what happens to the Antarctic ice sheet in the future will determine the rate and amount of global sea level rise.

What are your data, and how do you obtain them?

I use computer models that simplify the interactions between ice sheet and the climate, in order to reconstruct ice-sheet dynamics. We need to be confident that these models can adequately represent past time periods, though, before we can trust the computer model predictions of future Antarctic mass loss and sea level rise. Therefore, we validate these computer models by comparing them to geologic records of ice sheet behavior. My previous research project interpreted ice sheet dynamics and retreat patterns by mapping features that fast-moving ice-streams carved into the ground throughout the last glacial cycle. This information is used to calibrate the ice sheet model, ensuring that the model is physically realistic and reconstructs the same ice sheet retreat pattern as I interpret from the geologic record.

The  animation below shows a computer model projection for future sea level rise up to the year 2500. Here, the model assumes business-as-usual carbon emissions until the year 2100 (following ‘Representative Carbon Pathway’ RCP8.5). Even though the model’s carbon emissions are held constant after the year 2100, it takes the Antarctic ice sheet decades to centuries to fully respond to the high-CO2 forcing, leading to a huge amount of sea level rise. You can see the ice sheet (blue) get thinner and retreat, exposing the land (brown) of the continent underneath. I made this animation as part of a project to predict future sea level for the city of Boston; you can learn more about this project here, and see the full video I made here.  This is an example of how ice sheet computer models are used to predict future impacts of our modern decisions about carbon emissions.

 

What is your favorite part about being a scientist?

One of my favorite parts about being a scientist is the international community. When I go to conferences, or participate in field work, I am always in the company of international colleagues who become friends. I learn so much about science, but also about culture and history I would not be exposed to otherwise. Another favorite part of being a scientist is the opportunity to travel to amazing places, like Antarctica!

What advice would you give to young aspiring scientists?

My biggest piece of advice to young scientists (and to everyone) is: ASK STUPID QUESTIONS. Yes, there is such a thing as a stupid question, but no, it doesn’t mean that you are stupid. It means that you care more about understanding a concept and broadening your mind than what the people around you think. It’s hard – I still struggle with this, especially in a public setting like a class or lecture – but it’s so important. Asking stupid questions is by far the #1 easiest way to learn anything new, and often leads to the best conversations you’ll ever have. If you have a stupid question but feel embarrassed, just remember that there is a 99% chance that someone around you is wondering the same thing but is too shy to ask.

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