This artist’s concept depicts the Surface Water and Ocean Topography (SWOT) satellite, launched in December 2022. Credit: NASA/Jet Propulsion Laboratory
This artist’s concept depicts the Surface Water and Ocean Topography (SWOT) satellite, launched in December 2022. Credit: NASA/Jet Propulsion Laboratory
Tyler O'Neal, Staff Editor APPLICATIONS

Machine Learning can translate sea surface heights into climate change insights

Scientists have developed a new machine learning technique that can translate satellite data on sea surface heights into insights on climate change, heat flow, and current flow. The Surface Water and Ocean Topography (SWOT) satellite, launched in December 2022, captures snapshots of sea surface heights at an unprecedented level of detail. The new technique uses a convolutional neural network to estimate various aspects of current flow in the upper ocean, which can help scientists gain a better understanding of and predict climate change.

Oceanographers rely on satellite technology to monitor the ocean's surface elevation and map the circulation of its currents to understand the role of this movement in climate change and heat transport. In late 2022, the Surface Water and Ocean Topography (SWOT) satellite was launched to capture high-resolution snapshots of sea surface heights at a scale of tens of kilometers. However, this high level of detail has resulted in the detection of waves beneath the surface, making it challenging to use simple physics-based approaches to translate sea surface heights into meaningful information about ocean currents.

To address this challenge, researchers Xiao et al. have developed a novel machine learning method that uses SWOT sea surface height data to estimate various aspects of current flow in the upper ocean. The method applies a computational approach inspired by human vision known as a convolutional neural network, which the team trained on data from realistic simulations of sea surface heights and current dynamics.

The researchers have shown that their convolutional neural network can use detailed sea surface heights to estimate certain aspects of current flow. By gaining a better understanding of how currents transport heat and carbon, scientists may be able to predict and comprehend climate change more accurately.

However, the researchers acknowledge that this is only a proof of concept, and further research is needed to refine the new method before it can be reliably used with SWOT data.

Meanwhile, SWOT will continue to capture high-resolution images not only of Earth's oceans but also of almost all surface water around the world, including lakes, rivers, and reservoirs.

Electron micrographs of the 2D-0D hybrid surface implemented in this study (top left), memory characteristics generated by light pulses (top right), and polynomial memory characteristics generated by multiple light pulses (bottom).
Electron micrographs of the 2D-0D hybrid surface implemented in this study (top left), memory characteristics generated by light pulses (top right), and polynomial memory characteristics generated by multiple light pulses (bottom).

KIST develops tech to store, manipulate electronic states in quantum dots that are smaller than 10 nm, ushering in the era of light-powered multi-level memories

Tyler O'Neal, Staff Editor APPLICATIONS

Researchers from the Korea Institute of Science and Technology (KIST) and the Daegu Gyeongbuk Institute of Science and Technology (DGIST) have successfully developed a new semiconductor material that can store and manipulate electronic states in quantum dots measuring 10 nanometers or less. This new material makes it possible to store and manipulate data using light, rather than electrical signals, between the computing and storage components of a multi-level computer, thereby significantly enhancing processing speed. The development of this new multi-level optical memory device is expected to contribute towards accelerating the industrialization of next-generation system technologies, such as artificial intelligence systems.

We are facing an overwhelming amount of data. The data centers that store and process this data consume a lot of electricity, which is a major contributor to environmental pollution. To overcome this issue, researchers are exploring polygonal computing systems that have lower power consumption and higher computation speed. However, these systems are unable to handle the huge demand for data processing as they operate with electrical signals, similar to conventional binary computing systems.

Recently, the Korea Institute of Science and Technology (KIST) announced that Dr. Do Kyung Hwang of the Center for Opto-Electronic Materials & Devices and Professor Jong-Soo Lee of the Department of Energy Science & Engineering at Daegu Gyeongbuk Institute of Science and Technology (DGIST) have jointly developed a new semiconductor artificial junction material that can power next-generation memory with light. Transmitting data between the computing and storage parts of a multi-level computer using light instead of electrical signals can significantly increase processing speed.

The research team has created a new semiconductor artificial junction material by joining quantum dots in a core-shell structure with zinc sulfide (ZnS) on the surface of cadmium selenide (CdSe) and a molybdenum sulfide (MoS2) semiconductor. The new material enables the storage and manipulation of electronic states within quantum dots measuring 10 nm or less.

When light hits the cadmium selenide core, some electrons flow out of the molybdenum sulfide semiconductor, trapping holes in the core and making it conductive. The electron state inside cadmium selenide is also quantized. Intermittent light pulses trap electrons in the electron band one after the other, causing a change in the resistance of the molybdenum sulfide through the field effect. The resistance changes cascade depending on the number of light pulses, allowing for more than 0 and 10 states to be maintained, unlike conventional memory which only has 0 and 1 states. The zinc sulfide shell also prevents charge leakage between neighboring quantum dots, allowing each single quantum dot to function as a memory.

Unlike quantum dots in conventional 2D-0D semiconductor artificial junction structures that amplify signals from light sensors, the team's quantum dot structure perfectly mimics the floating gate memory structure, confirming its potential for use as a next-generation optical memory. The researchers verified the effectiveness of the polynomial memory phenomenon with neural network modeling using the CIFAR-10 dataset and achieved a 91% recognition rate.

Dr. Hwang of KIST says that this new multi-level optical memory device will contribute to accelerating the industrialization of next-generation system technologies such as artificial intelligence systems. These systems have been difficult to commercialize due to technical limitations arising from the miniaturization and integration of existing silicon semiconductor devices.

Extreme events such as cyclones will change as a result of climate change - and their effects should be better considered in climate models, say the authors. Photo: Viks_jin/NASA/Adobe Stock
Extreme events such as cyclones will change as a result of climate change - and their effects should be better considered in climate models, say the authors. Photo: Viks_jin/NASA/Adobe Stock

Germany is utilizing supercomputing to demo the impact of weather phenomena on ocean circulation

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The impact of climate change on atmospheric synoptic variability (ASV) will have significant consequences on ocean circulation and ecosystems. Even though ASV is often considered as background noise in climate models, it is important to comprehend its complete influence on the ocean. The future changes in ASV will result in a shallower mixing layer in subtropical regions and a deeper mixing layer in equatorial regions.

A recent study conducted by GEOMAR in Kiel, Germany, has explored how changes in weather patterns may affect the tropical Pacific Ocean and its ecosystems in the future. The researchers conducted simulations based on complex supercomputer models to show that these changes will have significant consequences on ocean circulation. The authors stress the need to consider this while creating future climate models.

The strength of the wind has a crucial influence on ocean circulation, especially during extreme weather events such as storm fronts, tropical storms, and cyclones. Due to climate change, these weather patterns are expected to change in the future, particularly in terms of the average energy input into the ocean from mid-latitude storms, which is expected to decrease while equatorial regions will become more active. Scientists refer to these distinct weather patterns as "Atmospheric Synoptic Variability" (ASV).

Dr. Olaf Duteil from the GEOMAR Helmholtz Centre for Ocean Research in Kiel and Professor Dr. Wonsun Park from the IBS Center for Climate Physics and Pusan National University in Korea have now conducted a modeling study to investigate the integrated effects of long-term changes in these weather patterns on the Pacific basin for the first time. According to their supercomputing results, it is crucial to consider these changes while creating climate models.

From a climate perspective, weather is generally regarded as "noise" and is not systematically analyzed in long-term climate projections, according to the two researchers. However, to better understand the influence of climate change on the ocean, it is essential to take into account the cumulative effect of short-term changes in weather patterns rather than just focusing on average atmospheric properties such as mean wind speeds, says Duteil.

According to the researchers, the Atmospheric Synoptic Variability (ASV) will play a vital role in the future mixing of the ocean's layers. Depending on the weather phenomena, the amount of kinetic energy input into the ocean can be either less or more, leading to less or more mixing, respectively. The study predicts that the reduction of ASV in subtropical regions will cause a shallowing of the mixing layer in the ocean. However, the mixing layer will become deeper at the equator with an increase in ASV.

The research findings also indicate that a decrease in ASV in the future will weaken the subtropical and tropical cells, affecting large-scale ocean circulation systems. These systems connect mid-latitudes and equatorial latitudes via upper ocean pathways, driven by the trade winds north and south of the equator. The study further highlights that these cells regulate the upwelling of equatorial waters and play a vital role in determining the surface temperature of the oceans, thus influencing primary productivity in the tropics.

The study emphasizes the importance of accurately quantifying ASV and weather patterns in climate models, which could improve our understanding of future upper ocean circulation and mean properties. The lead author, Duteil, suggests that this quantification should be used to enhance our confidence in projections of future climate, especially while analyzing large ensembles of climate models.