Improving predictions of sea level rise for the next century

When we ponder of air change one of the most dramatic images that comes to mind is the loss of glacial ice. As the Earth warms these huge rivers of ice befit a accident of the rising temperatures. But as ice sheets retreat they also befit an significant contributor to one the more dangerous outcomes of air change: sea-level rise. At MIT an interdisciplinary team of scientists is determined to better sea level rise prophesyions for the next century in part by taking a closer look at the physics of ice sheets.

Last month two investigation proposals on the question led by Brent Minchew the Cecil and Ida Green Career Development Professor in the Department of Earth Atmospheric and Planetary Sciences (EAPS) were announced as finalists in the MIT Climate Grand Challenges set. Launched in July 2020 Climate Grand Challenges fielded almost 100 project proposals from collaborators athwart the Institute who heeded the bold direct: to educe investigation and alterations that will liberate game-changing advances in the worlds efforts to address the air challenge.

As finalists Minchew and his collaborators from the departments of Urban Studies and Planning Economics Civil and Environmental Engineering the Haystack Observatory and outer partners accepted $100000 to educe their investigation plans. A subset of the 27 proposals tapped as finalists will be announced next month making up a portfolio of multiyear "flagship" projects receiving additional funding and support.

One goal of both Minchew proposals is to more fully apprehend the most primary processes that rule quick changes in glacial ice and to use that apprehending to build next-generation models that are more prophesyive of ice sheet conduct as they reply to and influence air change.

’We need to educe more careful and computationally efficient models that fit testable projections of sea-level rise over the coming decades. To do so quickly we want to make better and more many observations and acquire the physics of ice sheets from these data’ says Minchew. ’For sample how much force do you have to adduce to ice precedently it breaks?’

Currently Minchews Glacier Dynamics and Remote Sensing cluster uses satellites to remark the ice sheets on Greenland and Antarctica primarily with interferometric synthetic opening radar (InSAR). But the data are manyly calm over long intervals of time which only gives them "precedently and behind" snapshots of big events. By taking more many measurements on shorter time layers such as hours or days they can get a more detailed picture of what is happening in the ice.

’Many of the key unknowns in our projections of what ice sheets are going to look like in the forthcoming and how theyre going to evolve implicate the dynamics of glaciers or our apprehending of how the flow despatch and the resistances to flow are kindred’ says Minchew.

At the core of the two proposals is the creation of SACOS the Stratospheric Airborne Climate Observatory System. The cluster envisions educeing solar-powered drones that can fly in the stratosphere for months at a time taking more many measurements using a new lightweight low-power radar and other high-resolution instrumentation. They also offer air-dropping sensors straightly onto the ice equipped with seismometers and GPS trackers to measure high-frequency vibrations in the ice and pinpoint the motions of its flow.

How glaciers conduce to sea level rise

Current air models prophesy an increase in sea levels over the next century but by just how much is quiet unclear. Estimates are anywhere from 20 centimeters to two meters which is a big separation when it comes to enacting plan or mitigation. Minchew points out that response measures will be different depending on which end of the layer it falls toward. If its closer to 20 centimeters coastal barriers can be built to defend low-level areas. But with higher surges such measures befit too costly and inefficient to be viable as whole portions of cities and millions of nation would have to be relocated.

’If were looking at a forthcoming where we could get more than a meter of sea level rise by the end of the century then we need to know almost that sooner rather than later so that we can set to plan and to do our best to fit for that scenario’ he says.

There are two ways glaciers and ice sheets conduce to rising sea levels: direct melting of the ice and accelerated transport of ice to the oceans. In Antarctica warming waters melt the margins of the ice sheets which tends to lessen the resistive forcees and allow ice to flow more quickly to the ocean. This thinning can also cause the ice shelves to be more disposed to fracture facilitating the calving of icebergs — events which sometimes cause even further acceleration of ice flow.

Using data calm by SACOS Minchew and his cluster can better apprehend what material properties in the ice allow for fracturing and calving of icebergs and build a more complete picture of how ice sheets reply to air forces. 

’What I want is to lessen and quantify the uncertainties in projections of sea level rise out to the year 2100" he says.

From that more complete picture the team — which also includes economists engineers and urban planning specialists — can work on educeing prophesyive models and orders to help communities and rulements estimate the costs associated with sea level rise educe sound infrastructure strategies and spur engineering alteration.

Understanding glacier dynamics

More many radar measurements and the assembly of higher-resolution seismic and GPS data will allow Minchew and the team to educe a better apprehending of the wide state of glacier dynamics — including calving an significant process in setting the rate of sea level rise which is currently not well understood.  

’Some of what were doing is perfectly correspondent to what seismologists do’ he says. ’They measure seismic waves following an earthquake or a volcanic outburst or things of this essence and use those observations to better apprehend the mechanisms that rule these phenomena.’

Air-droppable sensors will help them collate information almost ice sheet motion but this order comes with drawbacks — like installation and livelihood which is hard to do out on a solid ice sheet that is moving and melting. Also the instruments can each only take measurements at a one location. Minchew equates it to a bobber in water: All it can tell you is how the bobber moves as the waves derange it.

But by also taking continuous radar measurements from the air Minchews team can collate observations both in space and in time. Instead of just watching the bobber in the water they can effectively make a movie of the waves propagating out as well as visualize processes like iceberg calving happening in multiple dimensions.

Once the bobbers are in locate and the movies recorded the next step is educeing machine acquireing algorithms to help analyze all the new data being calm. While this data-driven kind of discovery has been a hot question in other fields this is the leading time it has been applied to glacier investigation.

’Weve educeed this new orderology to ingest this huge amount of data’ he says ’and from that form an wholely new way of analyzing the method to reply these primary and critically significant questions.’