A new study published in Nature, led by Monash University researcher Dr. Felicity McCormack of Securing Antarctica’s Environmental Future (SAEF), examines how reliably scientists can predict future ice loss from Antarctica and how those predictions could improve sea level planning.

Antarctica’s Potential Impact on Global Sea Levels

Reports from the Intergovernmental Panel on Climate Change (IPCC) indicate that global sea levels could rise by more than two meters by 2100 under high emission scenarios if large parts of the Antarctic Ice Sheet collapse.

An increase of that scale would put one quarter of Australian residential properties at risk of flooding. It could also make large areas of sovereign territory across the Pacific uninhabitable and force hundreds of millions of people worldwide to leave their homes. Such an outcome would rank among the largest humanitarian and economic crises in history.

Despite the scale of the threat, the path of sea level rise through 2100 remains highly uncertain. Much of that uncertainty comes from the difficulty of determining how quickly Antarctica will lose ice.

In a worst-case scenario, the IPCC has estimated that the rate of sea level rise caused by Antarctic ice loss alone could almost double over the next 30 years. Until now, however, researchers have lacked a strong estimate of how much Antarctica may contribute to rising seas during the next several decades, the period most relevant to government policy and coastal planning.

Testing How Far Ahead Ice Loss Can Be Predicted

The research focused on two central questions: how much ice Antarctica may lose over the next 30 to 50 years, and whether that loss can be predicted with enough confidence to give governments and nations time to prepare.

To address these questions, the team evaluated how predictable sea level rise was across a range of ice sheet model projections during this relatively near-term period.

According to Dr. McCormack, Antarctic ice loss remains strongly and consistently predictable until around the middle of the century. This means models may be able to provide dependable estimates of Antarctica’s contribution to sea level rise during the decades most important for adaptation planning.

“If ice sheet models accurately reproduce the rates of ice loss we observe today, we can have confidence in using those same models to reliably predict Antarctica’s contribution to sea level rise over the next 30 to 50 years. Accurately predicting how much and how fast global sea levels will rise offers vital information for future coastal planning and government policy,” said Dr. McCormack.

Predictability Declines Later in the Century

That confidence weakens toward the end of the 21st century, when physical processes capable of rapidly increasing ice loss become more likely.

Some Antarctic ice rests on bedrock that lies below sea level. If this ice begins retreating quickly, the process can become difficult to stop or reverse. Once underway, it could produce far greater ice loss than near-term climate projections alone would suggest.

“The research findings provide a roadmap for future climate planning. By improving how ice sheet models represent critical physical processes that lead to rapid ice sheet retreat, we can narrow the deep uncertainty that hampers reliability of long-term sea level rise projections,” Dr. McCormack said.

The findings suggest that a meaningful opportunity for climate action still exists. Over the next three decades, sea level rise pathways are relatively well constrained, making this period especially important for long-range adaptation and infrastructure planning.

A Critical Window for Climate Action

Professor Steven Chown, Director of SAEF, said the world should use this period of greater predictability to act and invest in stronger systems for monitoring Antarctica.

“The predictability identified in this research does not reduce long-term risk; instead, it provides a defined period in which to act with greater confidence. Improvements in observational systems and ice sheet model developments will directly translate into more reliable sea level projections for short-term planning horizons,” Professor Chown said.

Professor Chown also said Australia is in a strong position to work with Indo-Pacific partners and help turn the findings into practical adaptation strategies.

“Pacific Island governments require reliable near-term projections to make decisions about infrastructure, community relocation, and long-term land use. Engagement on sea level science and adaptation planning represents a foreign policy opportunity and a regional responsibility,” Professor Chown said.

Turning Ice Sheet Forecasts Into Policy

Dr. McCormack said it is essential to create a clear process for incorporating ice sheet model projections into policies addressing sea level rise.

“When models replicate present-day observations of Antarctic ice mass loss, their projected ice mass loss rates over the coming several decades provide a reliable foundation for planning and adaptation, while longer-term sea level rise uncertainties highlight the need for ongoing development,” Dr. McCormack said.

The researchers argue that Antarctic forecasts may be most useful when presented across two distinct time periods: short-term ice loss that can be predicted with greater confidence, and longer-term change shaped by feedbacks that could rapidly accelerate retreat.

This two-stage approach could give policymakers a clearer basis for preparing for rising seas while also recognizing the much greater uncertainty that develops later in the century.

About Securing Antarctica’s Environmental Future

Securing Antarctica’s Environmental Future is a Monash-led research and workforce development program that forms a central part of the Australian Antarctic Program. SAEF conducts Antarctic and Southern Ocean research intended to support Australians, neighboring countries in the Asia-Pacific, and communities around the world as the climate continues to change.

Building on earlier studies of PCET and PCEnT, a team led by Prof. Kaifeng Wu at the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences investigated another important but poorly understood process: triplet energy transfer linked to proton movement.

Triplet energy transfer is a major pathway for moving energy in both natural and synthetic systems, but it operates differently from singlet energy transfer. Understanding how proton motion influences this process could open new ways to control energy flow in advanced materials.

In a study published in Nature Materials, the researchers reported a previously unknown mechanism called proton shuttle-assisted triplet energy transfer (PS-TET). The process was observed as energy moved from ZnSe-based colloidal quantum dots (QDs) to phenol-pyridine dyadic acceptors attached to their surfaces.

How the Proton Shuttle Moves Energy

When the ZnSe QDs absorb light, they enter an excited state. A hole then moves from ZnSe to phenol while a proton simultaneously shifts from phenol to pyridine.

Next, an electron transfers from ZnSe to the phenoxyl radical. At the same time, the proton moves back from pyridinium to its original location. Together, these linked steps produce the overall movement of spin-triplet energy from the ZnSe QDs to the phenol-pyridine dyads.

The proton ultimately ends up where it started, but its temporary movement has a major effect. The shuttle greatly increases both the speed and efficiency of triplet energy transfer compared with a methylated analog that does not contain the proton shuttle.

The team also found that adding a strongly electron-withdrawing trifluoromethyl substituent to pyridine can change the order in which the proton-coupled electron and hole transfer steps occur.

Quantum Tunneling at Room Temperature

The rate of PS-TET changed very little with temperature. This suggests that the proton does not move through a conventional heat-driven process. Instead, it appears to travel through quantum mechanical tunneling.

Calculations involving proton vibrational wavefunction overlap integrals supported this interpretation. These integrals help determine which excited-state relaxation pathways are favored and steer the system toward efficient triplet energy migration.

The findings show that quantum effects can be used to control charge and energy transfer in complex materials even at room temperature.

Potential Uses in Solar Cells, Lasers, and Catalysis

“The discovery of the PS-TET mechanism has profound implications for many modern molecular technologies involving the spin-triplet excited states of molecules,” Prof. Wu noted.

Increasing triplet generation efficiency could improve photoredox and environmental catalysis. In other technologies, however, triplet formation may need to be limited. Organic optoelectronic devices such as solar cells and lasers can perform better when unwanted triplet states are suppressed.

The study suggests that scientists may be able to tune triplet formation as needed. Creating a proton shuttle could enhance the process, while removing the shuttle could reduce or prevent it.

MIT researchers have now developed an approach that could lead to smaller, more durable lidar sensors that operate without any moving parts. Their advance centers on a new silicon-photonics chip, a type of semiconductor device that controls light instead of electrical signals.

Existing lidar systems built with silicon-photonics chips usually have a narrow field of view. As a result, they struggle to scan areas located toward the edges of a scene. Previous attempts to expand this viewing range have often introduced extra noise and reduced measurement accuracy.

The MIT team addressed those problems by creating an array of integrated antennas that greatly limits unwanted crosstalk, which occurs when neighboring antennas interfere with one another. The design allows the chip to scan across a broader field of view while producing less noise than other silicon-photonics-based methods.

A Smaller Lidar System With a Wider View

The advance could support the development of more capable lidar sensors for challenging uses, including autonomous vehicle navigation, aerial mapping, and the monitoring of construction sites.

“The functionality we demonstrated in this work solves a fundamental problem for integrated optical-phased-array technology, enabling future lidar sensors that can achieve significantly higher performance than we could demonstrate previously,” says Jelena Notaros, the Robert J. Shillman Career Development Associate Professor of Electrical Engineering and Computer Science (EECS) at MIT, a member of the Research Laboratory of Electronics, and senior author of a paper on this innovation.

The study also includes lead author and EECS graduate student Henry Crawford-Eng, along with EECS graduate students Andres Garcia Coleto, Benjamin M. Mazur, Daniel M. DeSantis, and Tal Sneh. The findings were published recently in Nature Communications.

How Lidar Maps Its Surroundings

Many traditional lidar systems use a large rotating unit to direct light pulses across a scene. When the light strikes nearby objects, it reflects back toward the sensor. The returning signals provide the information needed to reconstruct a detailed map of the environment.

Silicon-photonics-based lidar works differently. Rather than rotating a mechanical device, it scans a beam of light electronically in several directions with a system known as an integrated optical phased array (OPA).

At the heart of an OPA is a group of integrated antennas. Each antenna contains tiny, regularly spaced variations along its length. These features, known as corrugations, cause light from an input source to scatter upward and out of the photonic chip.

Researchers can control the direction of the outgoing beam by changing the phase of the light sent to each antenna. Adjusting these phases changes the angle at which the array releases light, making it possible to steer the beam without moving any physical components.

The Antenna Spacing Problem

Placing the antennas close together creates a serious obstacle. Neighboring antennas can couple with one another, scrambling the light they produce. Engineers have traditionally prevented this interference by increasing the distance between antennas, but wider spacing creates a different set of problems.

When antennas are too far apart, the array produces several copies of the same beam at different angles. The primary beam can only be moved a limited distance before it becomes difficult to distinguish from these additional copies.

“This limits our field of view, so the autonomous vehicle now only knows what is in front of it for a certain angular range,” Garcia Coleto explains.

The unwanted beam copies, called grating lobes, can confuse the sensor and generate false detections. They also consume energy that could otherwise be directed into the main beam.

To overcome this tradeoff, the MIT researchers developed antennas with reduced crosstalk that can be positioned close together without strongly coupling.

Three Antenna Shapes Reduce Interference

In a conventional OPA, every antenna has an identical structure and uses the same pattern of corrugations. When these matching antennas are placed close together, they interact very strongly.

The MIT team instead created a repeating set of three antennas with distinct shapes. They changed the width of the antennas as well as the size and placement of the corrugations. Because the antennas have different geometries, each one also has a different propagation coefficient, which describes how light moves through the structure.

“Because the antennas have very different propagation coefficients, when we put them close together, essentially each antenna doesn’t ‘see’ the antenna next to it. Therefore, it won’t couple with its neighbor,” Garcia Coleto says.

Making Different Antennas Behave the Same Way

Reducing the coupling was only part of the challenge. Although the antennas needed different propagation coefficients, they still had to release light in the same consistent manner.

The team designed the antennas around three essential requirements.

Each antenna had to emit the same amount of light. Every antenna also needed to release its beam at the same angle when receiving the same wavelength. Finally, the angle of emission had to change evenly across the entire array as the beam was steered.

“We have this challenge where we require the antennas to have different geometries to reduce the crosstalk, but we need to simultaneously design the antennas to have the same emission characteristics. While it is possible to engineer this, it is extremely difficult because, typically, when antennas are designed with different geometries, they tend to behave differently,” Crawford-Eng says.

The researchers began by developing the basic electromagnetic theory describing how radiative modes couple. They then used this theoretical framework to guide the design and computer simulation of the antennas.

Based on those calculations, the team manufactured an OPA containing the reduced-crosstalk antennas. The antennas were placed much closer together than those in a conventional system, and the completed device was then tested experimentally.

Interference Falls From About 100 Percent to 1 Percent

Under the conditions of the experiment, a typical OPA would have produced coupling of approximately 100 percent. The MIT design lowered that coupling to about 1 percent while still generating one clean and precise beam.

The system accurately steered the beam across a broad field of view without producing any grating lobes. This combination of wide scanning, low interference, and strong beam quality addresses one of the central obstacles facing integrated lidar technology.

The researchers now plan to refine the method so the system can cover an even broader viewing range. They are also studying another possible approach to wide field-of-view performance that emerged while they were developing the underlying theory.

“This work addresses a longstanding challenge in integrated optical phased arrays: simultaneously achieving both a wide field of view, which requires dense antenna spacing, and high beam quality, which requires low crosstalk between neighboring antennas. The authors solve this problem with an elegant antenna design. Their innovation is an important step forward for chip-scale, solid-state beam-steering technology,” says Joyce Poon, professor of electrical and computer engineering at the University of Toronto and director of the Max Planck Institute of Microstructure Physics, who was not involved with this work.

The Semiconductor Research Corporation, the National Science Foundation, an MIT MathWorks Fellowship, the U.S. Department of War, and the MIT Rolf G. Locher Endowed Fellowship supported the research, in part.

Some of the work was carried out using MIT.nano facilities.