A Year in Review: New Earth Discoveries in 2022
Image Credit: NASA/NOAA/NESDIS
Each year, the Earth Science Division’s Research and Analysis Program combines space, airborne, and ground-based observations with data processing from high-tech computer models and algorithms to uncover new things about the Earth. Explore some of our top discoveries of 2022, ranging from predicting volcanic eruptions to measuring rates of groundwater depletion and long-term monitoring of productivity in the Gulf of Maine, one of the fastest-warming bodies of water on Earth.
Using magma flow and surface deformation to predict volcanic eruptions
Forecasting volcanic eruptions, especially at scales longer than hours to days, is the ultimate challenge for volcanology. Volcanoes usually show signs of potential activity before an eruption; including gas emissions (degassing), shifts in the surface shape (deformation) and seismic activity collectively called ‘unrest’. However, while periods of unrest do usually precede an eruption, unrest can also cease without any eruption making it a poor predictor. Researchers found that the rate at which magma flows into the reservoir below a caldera that is showing signs of deformation is a much better predictor of eruption probability for the class of volcanoes studied. In all case studies magma flow estimated at > 0.1 km3 yr-1 was associated with an eruption within a year whereas when magma flow rates were less than 0.01 km3 yr-1 only 10% of cases erupted. While more needs to be done, including expanding this model to other volcano types, this could provide a viable means to use satellite data to provide timely advance notice of volcanic eruptions by incorporating viscoelastic overpressure models with surface deformation detected by InSAR and GNSS measurements.
Groundwater depletion in California’s Central Valley
Groundwater is a critical component of freshwater supplies for human life, for ecosystem and hydrological processes, for agricultural production, and more but in many regions of the world, it remains difficult to manage. California is the most populated, as well as the most productive agricultural region within the western region of the United States, both of which place heavy demands on freshwater resources. Over the past two decades, California has experienced repeated droughts leading to significant decreases in the surface water supplies. California’s Central Valley, a heavily agricultural region, depends on groundwater to provide two–thirds or more of irrigation water during periods of drought as compared to one-third or less under non-drought conditions. Sustained withdrawals of groundwater have led to falling water tables, drying wells, subsiding land, and its long-term disappearance. Nearly two decades of observations from the joint NASA- DLR GRACE satellite missio ns show that the rate of groundwater depletion in the Central Valley has been accelerating since 2003 (1.86 km3yr-1 for the period 1961–2021; 2.41 km3yr-1 for the period 2003–2021; 8.58 km3yr-1 for the period 2019–2021).
Associated Publication: Liu, P.-W., Famiglietti, J.S., Purdy, A.J. et al. (2022) Groundwater depletion in California’s Central Valley accelerates during megadrought. Nat Commun 13, 7825.
Drivers of the Exceptional Warmth in the Northern Hemisphere: Winter 2020
Much of northern Eurasia experienced record high temperatures during the first three months of 2020, and the eastern United States experienced a significant heat wave during March 2020. These episodes of extraordinary warmth reflect, to a large extent, the unusual persistence and large amplitude of three well-known modes of atmospheric variability: the Arctic Oscillation (AO), the North Atlantic Oscillation (NAO), and the Pacific–North American (PNA) pattern. The unusually long periods of warm temperatures in Eurasia and Europe were the result of forcings from the Indian Ocean and tropical Atlantic and tropical Pacific causing positive phases in both the Artic Oscillation and North Atlantic Oscillation. The strong heat wave that developed over eastern North America during March was primarily associated with an extreme negative phase of the Pacific- North American pattern again due to tropical forcing.
While, by definition, this exceptional warmth is a rare event, the approach used here allows the patterns in remote regions that significantly increase its likelihood to be identified. This approach can be an important tool for advancing prediction efforts, especially the prediction of extremes of societal relevance that occur on subseasonal time scales such as heat waves, floods, and flash droughts.
The persistent impacts of the eruption of Hunga Tonga-Hunga Hua’apai
The eruption of the submarine volcano Hunga Tonga-Hunga-Ha’apai on January 15, 2022 resulted in the lofting of aerosols and water vapor well into the upper stratosphere, an unprecedented event in the satellite era. Even more remarkable was the direct injection of water vapor by the eruption to altitudes as high as 53 km – above the stratopause - and exceeding stratospheric mean values of 4-6 ppmv by more than two orders of magnitude. The enhanced water vapor initially spread primarily southward, but within a month of the eruption in situ balloon sonde measurements in Costa Rica (10°N, 84°W) were showing highly elevated water vapor levels, and these elevations continued through at least January 2023. With stratospheric water vapor enhancements spreading into both hemispheres , the eruption of Hunga Tonga- Hunga Hua’apai could impact climate, though not through surface cooling due to sulfate aerosols, but through surface warming due to the radiative forcing from the enhanced stratospheric H2O.
Stauffer, R., J. Nicely, G. Taha, M. Damon, H. Selkirk, A. M. Thompson, D. Kollonige, H. Vömel, S. Davis and B. Johnson, Ticosonde: 17 Years of Balloon-borne Ozone and Water Vapor Profiles in Costa Rica. Presentation to the NASA SAGE III/ISS Science Team Meeting, NASA LaRC, October 13, 2022.
Investigating the effects of warming on Northern Hemisphere vegetation productivity
Climate change has had significant impacts on primary production across the Earth System. In the Northern Hemisphere, land primary productivity has been increasing, but whether this trend will continue into the future is unclear. As part of the Arctic-Boreal Vulnerability Experiment’s (ABoVE) international collaborations, modeling studies were conducted to investigate the effect of warming on Northern Hemisphere summer gross primary productivity for 2001–2100. In temperate and boreal regions, the relationship between summer gross primary productivity and temperature changes from positive to significantly negative before 2070 . This shift is attributed to summer temperatures exceeding the optimal temperature for vegetation growth. Through its significant impact on vegetation productivity later this century, predicted climate change could negatively impact the global land carbon sink. Arctic gross primary productivity, however, would continue to increase with increased summer warming.
Marine Cloud Brightening as a potential method of climate intervention
As Earth continues to warm and current pledges to decarbonize economies remain insufficient to limit warming below 1.5ºC, increasing attention is being given to the need for research into methods of climate intervention. One such method is Marine Cloud Brightening (MCB) in which which naturally occurring sea salt particles are artificially injected into the lower atmosphere to induce more marine clouds that reflect sunlight back into the space. This would temporarily cool the Earth, giving mitigation and adaptation efforts more time to scale up.
This research provides a framework to help organize, assess and prioritize future research on MCB, based on six physical science “checkpoints” that underpin the technical feasibility of MCB. Each check point has an associated “exit ramp” criteria and protocols for determining that a proposed intervention would not be technically or socially feasible and research should be terminated.
Although existing research has begun to address all of these themes, the road past these checkpoints is still long and arduous. International cooperation, collaboration, and data sharing will be necessary components of the climate intervention research enterprise. Planned or proposed investments in atmospheric research hold promise for developing the tools necessary to approach MCB decision-making thoughtfully, at least from the physical science side. Successful passage of the physical science checkpoints identified here would boost confidence in the potential for MCB to help cool the planet.
Antarctic calving loss rivals ice-shelf thinning in impact on ice-shelf buttressing
Antarctica’s ice shelves help to control the flow of glacial ice as it drains into the ocean, meaning that they also regulate the rate of global sea-level rise. The work behind this paper generated quantitative maps of Antarctic-wide spatially continuous coastlines showing annual ice shelf front positions from 1997 to 2021 using several optical-band, thermal-band and radar satellite sensors, combined with observations of ice flow. Over the time series studied, the Antarctic Ice Sheet experienced an overall loss of roughly 37,000 square kilometers of ice shelf area (approximately 1.9 % of the total area) that will not be fully replaced before the next onset of major iceberg calving events, which are projected to occur within the next 10 to 20 years. In this pan-Antarctic survey , the Getz Ice Shelf stands out for experiencing significant losses driven almost entirely by ice-shelf thinning. If the Antarctic Ice Sheet continues crumbling at its edges, marine ecosystems will be redefined, and a reorganized ocean circulation will impact primary productivity, water-mass formation and the delivery of heat to ice-shelf cavities. Modelling suggests that continued reductions in ice-shelf area around the continent could lead to a rise in sea-level similar to that which has been driven by ice-shelf thinning in recent years.
Associated Publication: Greene, C.A., Gardner, A.S., Schlegel, N.J. and Fraser, A.D., 2022. Antarctic calving loss rivals ice-shelf thinning. Nature, 609(7929), pp.948-953.
Irrigation and greening cause declines in albedo in High Mountain Asia
High Mountain Asia (HMA), a high-elevation geographical area that includes the Asian mountain ranges surrounding the Tibetan Plateau, hosts the world’s largest reservoirs of glaciers, ice, and snow outside the polar regions. The region encompasses many important and large river basins (e.g., the Ganges–Brahmaputra, the Indus, and the Yangtze) and is home to over a billion people, who rely on its water for agriculture, ecosystem preservation, livelihood, and energy. HMA is already experiencing the impacts of global warming including both changes in precipitation and increases in temperature. In addition, India and China have one of the highest rates of greening on Earth that could be attributed to changes in climate, land use, and land cover. Three factors, (1) decreased area covered by snow and ice, (2) increased amounts of dark green vegetation, and (3) increased amount of area supplied with irrigation, have caused a significant increase in the amount of radiation absorbed, rather than reflected, which is also referred to as a decrease in the surface albedo (the term for the proportion of reflected versus absorbed radiation). These surface albedo decreases, are likely to have a positive feedback impact on water resource requirements. A decrease in surface albedo can also lead to accelerated snow melt and more water available for vegetation growth, therefore, boosting greening. It is also important to account for this feedback in designing climate change mitigation strategies, as counterbalancing Earth’s warming could involve changes in agricultural (or managerial) practices such as practices such as irrigation.
Associated Publication: Maina, F.Z., Kumar, S.V. & Gangodagamage, C. Irrigation and warming drive the decreases in surface albedo over High Mountain Asia. Sci Rep 12, 16163 (2022).
Using global observing system simulation experiment (OSSE) simulations to determine saturation limits of observations to numerical weather predictions
Many different types of observations are taken every day to improve weather forecasting, including weather balloons, surface stations, and satellite instruments. One type of observation makes use of the Global Navigation Satellite System (GNSS) technology that is well known for locating the position of devices on the ground. By measuring how much a signal sent between two GNSS satellite platforms is bent, or refracted, by passing through the earth's atmosphere, the temperature and humidity of the atmosphere can be estimated.
In an attempt to determine the information content of GNSS observations and the associated predictability limit of current modeling systems, global observing system simulation experiment (OSSE) simulations were used to examine how much improvement might be seen in weather forecasting through acquisition of commercial GNSS-RO data, with the possibility of significantly increasing the quantity of observations. Different levels of up to 100,000 additional observations per day were simulated and tested in a weather prediction model. The results showed that there could be improvements in the forecast skill for temperatures and winds, with large improvements to the next day forecast, and smaller improvements to the 5-7 day forecast. The experiments showed some deficiencies in how the observations are used and illuminated some changes to the methodology that could result in better use of the GNSS observational data. This example illustrates the potential for using the OSSE to improve the capabilities of the data assimilation system . Future work may involve leveraging the OSSE framework to improve the use of GNSS-RO observations in the tropical stratosphere and lower troposphere.
Unexpected repartitioning of stratospheric chlorine
Smoke injected into the stratosphere by the massive 2020 Australian wildfires affected stratospheric chemical composition in a way never before seen. The greatest changes involved chemicals containing chlorine, which can affect stratospheric ozone amounts. Satellite data showed that lower stratospheric aerosol levels in the middle latitudes of the southern hemisphere more than doubled for about 5 months following the December-January fires. While the observations suggest there was some ozone depletion, observed changes in long-lived trace gases N2O, HF, and reactive chlorine species (Cly) indicate that atmospheric transport played a key role in the low ozone levels. Significantly, these results show that the Australian wildfire aerosols did not behave chemically like volcanic sulfate aerosols, and models can't reproduce the observed changes in the chlorine species from the wildfire aerosols.
A new method to detect changes in slow-moving landslides using InSAR timeseries
Landslides are a major natural hazard that occur worldwide and cause high economic losses and a large number of fatalities annually. Many investigations have been focused on causes, triggers, and predictions of rapid or catastrophic landslides. Slow-moving landslides move downslope at velocities that range from mm year−1 to m year−1 for months to hundreds of years. They cause damage to infrastructure, agriculture, and communities and can, at times, lead to a catastrophic high velocity collapse. However, they are often missed unless they fall are within an area that is intensely studied by long-term monitoring. By identifying these locations, the areas at greatest risk for landslides can be determined and appropriate policies can be developed.
Both remote sensing (light detection and ranging (lidar), interferometric synthetic aperture radar (InSAR), and optical remote sensing) and in situ (e.g. global navigation satellite system (GNSS), terrestrial laser scanners, geophysical methods) have been used to monitor slow-moving landslides. Here, a new method that uses InSAR displacement time series to identify slowly deforming areas and detect the moment that a deforming area begins to accelerate or decelerate is presented. This method differs from previous work in that InSAR detection analysis provides an objective way to construct multitemporal maps of unstable areas and an inventory of the timing of changes in deformation rate of unstable areas. The ability to determine the temporal and spatial variation of velocity changes is a step forward in the large-scale interpretation of the physical behavior of slow-moving deforming areas. Ultimately, this inventory of accelerations and decelerations can be used as a tool to shed light on the dynamics of slow-moving landslides at both sub-landslide and regional scales with high spatial and temporal resolution.
Associated Publication: Urgilez Vinueza, A., Handwerger, A.L., Bakker, M. and Bogaard, T., 2022. A new method to detect changes in displacement rates of slow-moving landslides using InSAR time series. Landslides, 19(9), pp.2233-2247.
Phytoplankton Productivity in the Gulf of Maine Down 65% Over 20 Years
The Gulf of Maine is one of Earth’s fastest-warming water bodies, driven by inflows of warm, salty water from the North Atlantic. Since 1998 over 215 research cruises across the widest part of the Gulf of Maine have collected sea-truth measurements for satellite measurements. The Gulf of Maine- North Atlantic Time Series (GNATS) data set now includes some of the warmest years in the Gulf of Maine on record, including the heatwaves of 2012, 2016, and 2018. It also includes the major elevated precipitation years of 2006–2010 which marked the beginning of a significant decrease in primary production Overall primary productivity of the Gulf of Maine has dropped by ~65% during first 20 years of GNATS (along with numerous other biogeochemical changes). The significant decrease in primary production will likely have negative impacts on the overall productivity of the higher trophic levels as well as fishery yields. However, the exact nature of the negative impacts on fishery yields are likely to vary over different marine ecosystems. These results suggest that the changes in the biology as well as the hydrography, chemistry, and bio-optics of the Gulf of Maine are fundamentally tied to changes of circulation of the warming North Atlantic Ocean.
