Jeremy Bassis

In fairness, mass conservation methods require surface mass balance and not only can that be hugely heterogeneous, we often have to model it based on a combination of very coarse climate model output and heavily parameterized models.

If you want to learn more about this, Tanner is going to talk about how he has applied this method to (nearly) every glacier in the wold next week at AGU and has new estimates of the total volume of glaciers worldwide.

This shouldn’t work, right? But not only does it work, we found that it was competitive with much more sophisticated (and data intensive) methods.

This is still kind of magic because we don’t use any information about snowfall, velocity or even ice temperature. We just use, essentially, maps of surface elevation at two different times and voila! Ice thickness.

So this is Tanner’s insight. If we have know surface elevation and surface elevation change—which we can increasingly measure from space—then we can use the old fashioned plastic approximation to *simultaneously* infer the yield strength and ice thickness. No unknown parameters.

Applying these more sophisticated methods requires that we make educated guesses about a bunch of unknown parameters. We also need to ingest a lot more data, most of which is either hard to get or prone to large errors in remote region.

Sadly, we also know that ice deformation is more complicated and more modern approaches to ice sheet dynamics take into account creep deformation, sliding amongst other processes.

This idea is a bit dated, but still occasionally used in data sparse regions. The problem is that you need to know the yield strength of ice and this is a parameter that varies within glaciers and even between glaciers.

Nye even used this plastic approximation to provide some of the first estimates of the ice thickness of the Greenland ice sheet. The idea is that you can infer the ice thickness if you know the yield strength and have measurements of surface elevation.

This paper is in the vintage glaciology tradition of our group and goes all the way back to work that John Nye did treating ice as a plastic material where ice is assumed to be rigid beneath a yield strength and then flows once the stress exceeds a material property called the yield strength.

Grad student Tanner May has a new fun paper out in the Journal of Glaciology that is kind of magical. The magic trick that Tanner performs is that he manages to estimate thickness of glaciers using only surface elevations and nothing else.

This shouldn't work, but it does. Let me tell you why.

I mean that was kind of the entire point of thread. Taps sign 👇

This is a use case where the switch to a heat pump will almost always save money! However, I've also seen a bunch of these properties switch to natural gas furnaces to reduce utility bills. The locks in natural gas burning for at least a decade and sometimes much longer.

At least here, the return on investment for insulating and air sealing is almost always high irrespective of the heat source. Insulate and air seal first before even considering a heat pump.

I think that's right. Gas prices can also be volatile, but a power outage could leave you with no heat if your sole heat source is an electric heat pump.

There have a lot of programs providing incentives that reduce the cost of installing a heat pump compared to a gas furnace, but we really need to also figure out how to price electricity so that lower and middle income folks can afford the utility bills to run heat pumps.

If you have a 100% electric house, you can eliminate gas completely and save all of the fees utilities charge, which helps keep heat pumps affordable.

The lifetime of the dual fuel heat pumps with backup gas furnaces are still 10-20 years so every install that uses gas for cold temperatures is going to continue to burn fossil fuels for the next 1-2 decades. And that is a problem.

You can do clever things with mini splits so that you are only heating the rooms you use. This helps some houses, but if gas is cheap, eventually it is cheaper to heat your home with a gas furnace. The default install here is using gas heat for cold temperatures because of this.

The first priority is always air sealing and insulating, especially the older homes. This means less energy consumed total and, depending on how far you go, usually is cost effective and improves comfort.

Eventually, it gets cold enough that it is much cheaper to heat your home with a gas furnace. For some places, gas is still expensive enough that heat pumps make sense. But almost most installs in Michigan are going to end up using gas heat for cold temperatures because of this.

But heat pumps become less efficient as it gets colder and they need to run harder and longer when it gets really cold and consume a lot of electricity. The problem is that in many places, like Michigan, natural gas is cheap compared to electricity.

First, air source heat pumps are great in climates that don’t get too cold. There are also strong cases for folks in cold climates that currently use resistive heat, oil or even propane. And unlike previous generations, today’s heat pumps can work down to very cold temperatures.

Heat pumps are a terrific technology, but I wish more people understood that there are regions where heat pumps don’t make economic sense and this has to change if we are going to electrify and decarbonize.

We are required to include all the names of folks that declined to write a letter in the casebook. Declining to write a letter, at least for us, isn't "evidence" as there are many reasons why someone might decline. But it isn't exactly neutral either.

I’m probably going to spend at least 3 days (maybe more) working on a letter. I wish candidates could read the letters because the ones I have read and written have been overwhelmingly positive.

I’m going to read (or re-read) your papers, focusing on recent papers I'm less familiar with. A roadmap to how things fit together makes my job easier because I'm looking for positives to highlight. I'm not probing for negatives.

One thing I'm going to write about is how your research program has continued to grow and evolve since grad/postdoc work. That could mean new research directions, collaborators or just building a foundation on previous work.

The best thing a candidate can do to help me write a strong letter is write strong research, service and teaching narratives that focuses on big picture and are not overly technical. What do you think are your most important contributions? How do they fit together? What are you most excited about?

Most letter requests include evaluation criteria. You should ask to see the template. Letters don’t have to be superlative, but direct quotes from letters often end up getting pulled into presentations and summary documents.