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NASA NTRS1991

Antarctic Sea ice variations and seasonal air temperature relationships

Data through 1987 are used to determine the regional and seasonal dependencies of recent trends of Antarctic temperature and sea ice. Lead-lag relationships involving regional sea ice and air temperature are systematically evaluated, with an eye toward the ice-temperature feedbacks that may influence climatic change. Over the 1958-1087 period the temperature trends are positive in all seasons. For the 15 years (l973-l987) for which ice data are available, the trends are predominantly positive only in winter and summer, and are most strongly positive over the Antarctic Peninsula. The spatially aggregated trend of temperature for this latter period is small but positive, while the corresponding trend of ice coverage is small but negative. Lag correlations between seasonal anomalies of the two variables are generally stronger with ice lagging the summer temperatures and with ice leading the winter temperatures. The implication is that summer temperatures predispose the near-surface waters to above-or below-normal ice coverage in the following fall and winter.

Weatherly, John W.↗

NASA NTRS1996

Decadal evolution of the Antarctic ozone hole

Ozone column amounts obtained by the total ozone mapping spectrometer (TOMS) in the southern polar region are analyzed during late austral winter and spring (days 240-300) for 1980-1991 using area-mapping techniques and area-weighted vortex averages. The vortex here is defined using the -50 PVU (1 PVU = 1.0 x 10(-6) K kg-1 m2 s-1) contour on the 500 K isentropic surface. The principal results are: (1) there is a distinct change after 1985 in the vortex-averaged column ozone depletion rate during September and October, the period of maximum ozone loss, and (2) the vortex-averaged column ozone in late August (day 240) has dropped by 70 Dobson units (DU) in a decade due to the loss in the dark and the dilution effect. The mean ozone depletion rate in the vortex between day 240 and the day of minimum vortex-averaged ozone is about 1 DU d-1 at the beginning of the decade, increasing to about 1.8 DU d-1 by 1985, and then apparently saturating thereafter. The vortex-average column ozone during September and October has declined at the rate of 11.3 DU yr-1 (3.8%) from 1980 to 1987 (90 DU over 8 years) and at a smaller rate of 2 DU yr-1 (0.9%) from 1987 to 1991 (10 DU over 5 years, excluding the anomalous year 1988). We interpret the year-to-year trend in the ozone depletion rate during the earlier part of the decade as due to the rise of anthropogenic chlorine in the atmosphere. The slower trend at the end of the decade indicates saturation of ozone depletion in the vortex interior, in that chlorine amounts in the mid-1980s were already sufficiently high to deplete most of the ozone in air within the isolated regions of the lower-stratospheric polar vortex. In subsequent years, increases in stratospheric chlorine may have enhanced wintertime chemical loss of ozone in the south polar vortex even before major losses during the Antarctic spring.

Non-NASA Center↗

NASA NTRS2012

Variability of Black Carbon Deposition to the East Antarctic Plateau, 1800-2000 AD

Refractory black carbon aerosols (rBC) from biomass burning and fossil fuel combustion are deposited to the Antarctic ice sheet and preserve a history of emissions and long-range transport from low- and mid-latitudes. Antarctic ice core rBC records may thus provide information with respect to past combustion aerosol emissions and atmospheric circulation. Here, we present six East Antarctic ice core records of rBC concentrations and fluxes covering the last two centuries with approximately annual resolution (cal. yr. 1800 to 2000). The ice cores were drilled in disparate regions of the high East Antarctic ice sheet, at different elevations and net snow accumulation rates. Annual rBC concentrations were log-normally distributed and geometric means of annual concentrations ranged from 0.10 to 0.18 m cro-g/kg. Average rBC fluxes were determined over the time periods 1800 to 2000 and 1963 to 2000 and ranged from 3.4 to 15.5 m /a and 3.6 to 21.8 micro-g/sq m/a, respectively. Geometric mean concentrations spanning 1800 to 2000 increased linearly with elevation at a rate of 0.025 micro-g/kg/500 m. Spectral analysis of the records revealed significant decadal-scale variability, which at several sites was comparable to decadal ENSO variability.

Bisiaux, M. M.↗

DOE OSTI2024

Ice-shelf freshwater triggers for the Filchner–Ronne Ice Shelf melt tipping point in a global ocean–sea-ice model

Abstract. Some ocean modeling studies have identified a potential tipping point from a low to a high basal melt regime beneath the Filchner–Ronne Ice Shelf (FRIS), Antarctica, with significant implications for subsequent Antarctic ice sheet mass loss. To date, investigation of the climate drivers and impacts of this possible event have been limited because ice-shelf cavities and ice-shelf melting are only now starting to be included in global climate models. Using a global ocean–sea-ice configuration of the Energy Exascale Earth System Model (E3SM) that represents both ocean circulations and melting within ice-shelf cavities, we explore freshwater triggers (iceberg melt and ice-shelf basal melt) of a transition to a high-melt regime at FRIS in a low-resolution (30 km in the Southern Ocean) global ocean–sea-ice model. We find that a realistic spatial distribution of iceberg melt fluxes is necessary to prevent the FRIS melt regime change from unrealistically occurring under historical-reanalysis-based atmospheric forcing. Further, improvement of the default parameterization for mesoscale eddy mixing significantly reduces a large regional fresh bias and weak Antarctic Slope Front structure, both of which precondition the model to melt regime change. Using two different stable model configurations, we explore the sensitivity of FRIS melt regime change to regional ice-sheet freshwater fluxes. Through a series of sensitivity experiments prescribing incrementally increasing melt rates from the smaller, neighboring ice shelves in the eastern Weddell Sea, we demonstrate the potential for an ice-shelf melt “domino effect” should the upstream ice shelves experience increased melt rates. The experiments also reveal that modest ice-shelf melt biases in a model, especially at coarse ocean resolution where narrow continental shelf dynamics are not well resolved, can lead to an unrealistic melt regime change at downstream ice shelves. Thus, we find that remote connections between melt fluxes at different ice shelves are sensitive to baseline model conditions. Our results highlight both the potential and the peril of simulating prognostic Antarctic ice-shelf melt rates in a low-resolution global model.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2024

Ice-shelf freshwater triggers for the Filchner–Ronne Ice Shelf melt tipping point in a global ocean–sea-ice model

Some ocean modeling studies have identified a potential tipping point from a low to a high basal melt regime beneath the Filchner–Ronne Ice Shelf (FRIS), Antarctica, with significant implications for subsequent Antarctic ice sheet mass loss. To date, investigation of the climate drivers and impacts of this possible event have been limited because ice-shelf cavities and ice-shelf melting are only now starting to be included in global climate models. Using a global ocean–sea-ice configuration of the Energy Exascale Earth System Model (E3SM) that represents both ocean circulations and melting within ice-shelf cavities, we explore freshwater triggers (iceberg melt and ice-shelf basal melt) of a transition to a high-melt regime at FRIS in a low-resolution (30 km in the Southern Ocean) global ocean–sea-ice model. We find that a realistic spatial distribution of iceberg melt fluxes is necessary to prevent the FRIS melt regime change from unrealistically occurring under historical-reanalysis-based atmospheric forcing. Further, improvement of the default parameterization for mesoscale eddy mixing significantly reduces a large regional fresh bias and weak Antarctic Slope Front structure, both of which precondition the model to melt regime change. Using two different stable model con figurations, we explore the sensitivity of FRIS melt regime change to regional ice-sheet freshwater fluxes. Through a series of sensitivity experiments prescribing incrementally increasing melt rates from the smaller, neighboring ice shelves in the eastern Weddell Sea, we demonstrate the potential for an ice-shelf melt “domino effect” should the upstream ice shelves experience increased melt rates. The experiments also reveal that modest ice-shelf melt biases in a model, especially at coarse ocean resolution where narrow continental shelf dynamics are not well resolved, can lead to an unrealistic melt regime change at downstream ice shelves. Thus, we find that remote connections between melt fluxes at different ice shelves are sensitive to baseline model conditions. Our results highlight both the potential and the peril of simulating prognostic Antarctic ice-shelf melt rates in a low-resolution global model.

58 GEOSCIENCES↗

NASA NTRS2002

On the Size of the Antarctic Ozone Hole

The Antarctic ozone hole is a region of extremely large ozone depletion that is roughly centered over the South Pole. Since 1979, the area coverage of the ozone hole has grown from near zero size to over 24 Million sq km. In the 8-year period from 1981 to 1989, the area expanded by 18 Million sq km. During the last 5 years, the hole has been observed to exceed 25 Million sq km over brief periods. In the spring of 2002, the size of the ozone hole barely reached 20 Million sq km for only a couple of days. We will review these size observations, the size trends, and the interannual variability of the size. The area is derived from the area enclosed by the 220 DU total ozone contour. We will discuss the rationale for the choice of 220 DU: 1) it is located near the steep gradient between southern mid-latitudes and the polar region, and 2) 220 DU is a value that is lower than the pre-1979 ozone observations over Antarctica during the spring period. The phenomenal growth of the ozone hole was directly caused by the increases of chlorine and bromine compounds in the stratosphere. In this talk, we will show the relationship of the ozone hole's size to the interannual variability of Antarctic spring temperatures. In addition, we will show the relationship of these same temperatures to planetary-scale wave forcings.

Newman, Paul A.↗

NASA NTRS2002

What Controls the Size of the Antarctic Ozone Hole?

The Antarctic ozone hole is a region of extremely large ozone depletion that is roughly centered over the South Pole. Since 1979, the area coverage of the ozone hole has grown from near zero size to over 24 Million square kilometers. In the 8-year period from 1981 to 1989, the area expanded by 18 Million square kilometers. During the last 5 years, the hole has been observed to exceed 25 Million square kilometers over brief periods. We will review these size observations, the size trends, and the interannual variability of the size. The area is derived from the area enclosed by the 220 DU total ozone contour. We will discuss the rationale for the choice of 220 DU: 1) it is located near the steep gradient between southern mid-latitudes and the polar region, and 2) 220 DU is a value that is lower than the pre- 1979 ozone observations over Antarctica during the spring period. The phenomenal growth of the ozone hole was directly caused by the increases of chlorine and bromine compounds in the stratosphere. In this talk, we will show the relationship of the ozone hole's size to the interannual variability of Antarctic spring temperatures. In addition, we will show the relationship of these same temperatures to planetary-scale wave forcings.

Bhartia, P. K.↗

DOE OSTI2025

The OCEAN ICE mooring compilation: a standardised, pan-Antarctic database of ocean hydrography and current time series

Continuous moored time series of temperature, salinity, pressure and current speed and direction are of great importance for understanding the continental shelf and under-ice-shelf dynamics and thermodynamics that govern water mass transformations and ice melting in and around Antarctic marginal seas. In these regions, icebergs and sea ice make ship-based mooring deployment and recovery challenging. Nevertheless, over decades, expeditions around the fringe of Antarctica sporadically deployed and recovered hundreds of moored instruments, including those facilitated through ice shelves boreholes. These datasets tend to be archived in a wide range of data centres, with, to our knowledge, no clear format standardisation. As a result, systematic analysis of historical mooring time series in the marginal seas is often challenging. Here we present the first version of a standardised pan-Antarctic moored hydrography and current time series compilation, with broad international contributions from data centres, research institutes and individual data owners. The mooring records in this compilation span over five decades, from the 1970s to the 2020s, providing an opportunity for a systematic study of the pan-Antarctic water mass transport and shelf connectivity. As a demonstration of the utility of this compilation, we present spectral analysis of the compiled current velocity time series, which unsurprisingly shows the dominating presence of tidal variability within most records. This component of the variability is fitted using multi-linear regression to tidal frequencies, and the tidal fit is removed from the original time series to leave de-tided variability. Given the limited record durations to months to years, de-tided variability is dominated by synoptic (3–10 d period), intraseasonal (10–80 d) and seasonal (∼6 months–1 year) signals. The spatial distribution of the kinetic energy integrated within frequency bands is presented and discussed within respective regional contexts, and future avenues of research are proposed. This data compilation is assembled under the endorsement of Ocean-Cryosphere Exchanges in ANtarctica: Impacts on Climate and the Earth System (OCEAN ICE) project (https://ocean-ice.eu/, last access: 23 October 2025) funded by the European Commission and UK Research and Innovation. It is available and regularly updated in NetCDF format with the SEANOE database at https://doi.org/10.17882/99922 (Zhou et al., 2024a).

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1997

Primary Production in Antarctic Sea Ice

A numerical model shows that in Antarctic sea ice, increased flooding in regions with thick snow cover enhances primary production in the infiltration (surface) layer. Productivity in the freeboard (sea level) layer is also determined by sea ice porosity, which varies with temperature. Spatial and temporal variation in snow thickness and the proportion of first-year ice thus determine regional differences in sea ice primary production. Model results show that of the 40 tera-grams of carbon produced annually in the Antarctic ice pack, 75 percent was associated with first-year ice and nearly 50 percent was produced in the Weddell Sea.

Arrigo, Kevin R.↗

NASA NTRS1994

Polar stratospheric cloud climatology based on Stratospheric Aerosol Measurement II observations from 1978 to 1989

The probability of polar stratospheric cloud (PSC) occurrence in the Antarctic and Arctic has been estimated using Stratospheric Aerosol Measurement (SAM) II aerosol extinction data from 1978 to 1989. Antarctic PSCs are typically observed by SAM II from mid-May to early November, with a maximum zonal average probability of about 0.6 at 18-20 km in August. The typical Arctic PSC season extends only from late November to early March, with a peak zonal average probability of about 0.1 in early February at 20-22 km. There is considerable year-to-year variability in Arctic PSC sightings because of changes in the dynamics of the northern polar vortex. Year-to-year variability in Antarctic sightings is most prominent in the number of late season clouds. Maximum PSC sighting probabilities in both polar regions occur in the region from 90 deg W through the Greenwich meridian to 90 deg E, where temperatures are coldest on average. Arctic sighting probabilities approach zero outside this region, but clouds have been sighted in the Antarctic at all longitudes during most months. Inferred PSC formation temperatures remain constant throughout the Arctic winter and are similar to those in early Antarctic winter. PSC formation temperatures in the Antarctic drop markedly in the 15 to 20-km region by September, a pattern consistent with the irreversible loss of HNO3 and H2O vapor in sedimenting PSC particles.

Poole, Lamont R.↗

NASA NTRS1982

Japanese MAGSAT team

Construction of a model of the regional magnetic field and investigation of the local magnetic anomalies and their origin were approaches used in attempts to study the crustal structure near Japan and its Antarctic bases. Spatial properties of the regional magnetic field and comparison of the regional model with that derived from MAGSAT data are discussed. Possible causes of the magnetic anomalies, and results of aeromagnetic surveys incorporating gravity and seismic data are explored. Ionospheric and magnetospheric contributions to geomagnetic variations, field-aligned currents, magnetic geomagnetic pulsations, and hydromagnetic waves by analysis of MAGSAT data are also examined.

Fukushima, N.↗

NASA NTRS1985

Satellite observations of sea ice

An overview is presented of Antarctic and Arctic sea ice studies using data from the Nimbus-5 ESMR and the Nimbus-7 SMMR passive microwave radiometers. Four years (1973-1976) of ESMR data for the Antarctic Ocean define the characteristics of the seasonal cycle including regional contrasts and interannual variations. Major advances include the discovery of the Weddell polynya and the presence of substantial areas of open water in the Antarctic winter pack ice. Regional differences in sea ice extent on time-scales of about a month are shown to be associated with variations in surface-wind fields. In the Arctic, the computation of sea ice concentration is complicated by the presence of multiyear ice, but the amount of multiyear ice becomes an important measurable quantity with dual-polarized, multifrequency passive microwave sensors. Analysis of SMMR data demonstrates its advantage for studying the spatial and temporal variability of the Arctic ice cover. Large observed interannual variations in the distribution of the multiyear pack ice and the presence of significant divergent areas in the central Arctic during winter contrast markedly with the classical view of the Arctic pack ice.

Cavalieri, D. J.↗

NASA NTRS2020

Metrics for Improved Reanalyses in Polar Regions

Atmospheric reanalyses are widely used for a variety of scientific endeavors in the Arctic and Antarctic. Reanalyses are used as boundary conditions for a regional and process-based models, for climate model validation, and for diagnostic analysis of physical processes, weather and climatic events. However, reanalyses are typically global and often do not account for specific, regional considerations, such as for polar regions. In this work, we provide a brief evaluation of a prototype for a new GMAO reanalysis, which incorporates higher spatial resolution, an updated approach for data assimilation, and a revised atmospheric model. We identify differences in the representation of the Arctic atmosphere in comparison to recent reanalyses. Furthermore, we provide a forum for Arctic scientists to consider the future improvements for reanalyses, and seek feedback for the following questions: 1) What are important performance factors to consider in evaluating new reanalyses? 2) What physical processes should be incorporated into new reanalyses? 3) What spatio-temporal scales should be considered?

Parker, Chelsea L.↗

DOE OSTI2025

Constraining Black Carbon Aging in Global Models to Reflect Timescales for Internal Mixing

The radiative effects of black carbon depend critically on its atmospheric lifetime, which is controlled by the rate at which freshly emitted combustion particles become internally mixed with other aerosol components. Global aerosol models strive to represent this process, but the timescale for aerosol mixing is not easily constrained using observations. In this study, we apply a timescale parameterization derived from particle‐resolved simulations to quantify, in a global aerosol model, the timescale for internal mixing. We show that, while highly variable, the average timescale for internal mixing is approximately 3 hr, which is much shorter than the 24‐hr aging timescale traditionally applied in bulk aerosol models. We then use the mixing timescale to constrain the aging criterion in the Modal Aerosol Module. Our analysis reveals that, to best reflect timescales for internal mixing, modal models should assume that particles transition from the hydrophobic (fresh) to the hydrophilic (aged) class once they accumulate a coating thickness equal to four monolayers of sulfuric acid, as opposed to the model's current aging criterion of eight monolayers. We show that, in remote regions like the Arctic and Antarctic, predictions of black carbon loading and its seasonal variation are particularly sensitive to the model representation of aging. By constraining aging in global models to reflect mixing timescales simulated by the particle‐resolved model, we eliminate one of the free parameters governing black carbon's long‐range transport and spatiotemporal distribution.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS2004

Ground Based Remote Sensing of Upper Atmosphere Dynamics, Thermodynamics and Composition in Support of TIMED Satellites Scientific Mission

The following research work was accomplished: 1. We operated high throughput spectrophotometers and interferometers at eight observatories in the Arctic, Antarctic and mid-latitude regions to record relatively high-resolution spectra of very low light level airglow and auroral line as well as band emissions. 2. Our Polar observations of auroral emissions from N2 and O emissions have been analyzed to derive the O/N2 ratios around 110 km height in the Polar thermosphere during different auroral events triggered by the precipitation of auroral electrons with average energy of about 10 keV. These results have been compared with similar ratios derived from TIMED satellite s GUVI measurements of N2 LBH and 01 1356A emissions. 3. Our airglow measurements show MLT density and temperature modulations by Planetary, Tidal and Gravity Waves. They also indicate Mesopause cooling preceding a Stratospheric Warming Event (SWE).

Source record↗

NASA NTRS2026

Changes in Arctic and Antarctic Sea-Ice Properties and Processes

Although sea ice covers ~9% of the world’s oceans, its presence, and absence, vastly alter the energetic balance of Earth’s climate. Because of geographic differences, Arctic and Antarctic sea ice have different dominant properties and processes, which produce different responses to natural variability and anthropogenic change. In this Review, we survey changes in sea-ice properties and processes of the Arctic and Antarctic environments. In the Arctic, the melt season has lengthened by ~7.4 days decade −1 (1979-2024). There has been a corresponding decrease in winter sea-ice thickness (1.6 m mean total over 1980-2023), summer surface albedo (0.03 decade −1 over 1979-2020), and spring snow depth (2.5 cm decade −1 over 1954-2024). In comparison, corresponding changes in the Antarctic are small overall due to contrasting regional and temporal trends. From a dynamic perspective, sea-ice motion in both hemispheres has increased, with 0.63 cm s −1 decade −1 in the Arctic (1978-2024) and 0.69 cm s −1 decade −1 in the Antarctic (1982-2024), whereas trends in polynya occurrence differ by region. Future research should prioritize sea-ice observations that can inform how the climate system responds to natural variability and anthropogenic change, be standardized to increase uptake by the broader scientific community, and target process-oriented interactions to support model development.

Melinda A Webster↗

NASA NTRS1986

Parent sources of Antarctic meteorites as inferred from pairing of the specimens

Antarctic meteorites may be derived from regions different than those from which comtemporary falls derive. If so, they are useful in reconstruction of their parent bodies or masses. To obtain a better understanding of the parent sources and their relation to asteroids, several Antarctic achondrites and unique chondrites were reinvestigated with electron microprobe and single crystal X-ray diffraction. Synthesis of their parent body was performed for three classes of meteorites on the basis of pairing of the specimens. The results are discussed for HED (Howardites, Eucrites, Diogenites) Parent Bodies, Ureilite Parent Bodies, and LL Chondrite Parent Bodies.

Takeda, H.↗

DOE OSTI2022

Aerosol iron speciation and seasonal variation of iron oxidation state over the western Antarctic Peninsula

The iron (Fe) speciation and oxidation state have been considered critical factors affecting Fe solubility in the atmosphere and bioavailability in the surface ocean. In this study, elemental composition and Fe speciation in aerosol samples collected at the Palmer Station in the West Antarctic Peninsula were determined using synchrotron-based X-ray fluorescence (XRF) and X-ray Absorption Near-Edge Structure (XANES) spectroscopy. The elemental composition of coarse-mode (>1 mu m) Fe-containing particles suggests that the region's crustal emission is the primary source of aerosol Fe. The Fe minerals in these aerosol particles were predominantly hematite and biotite, but minor fractions of pyrite and ilmenite were observed as well. The Fe oxidation state showed an evident seasonal variation. Further, the Fe(II) content accounted for 71% of the total Fe in the austral summer, while this fraction dropped to 60% in the austral winter. Multivariate linear models involving meteorological parameters suggested that the wind speed, relative humidity, and solar irradiance were the factors that significantly controlled the percentage of Fe(II) in the austral summer. On the contrary, no relationship was found between these factors and the Fe(II) percentage in the austral winter, suggesting that atmospheric photoreduction and regional dust emission were limited. Moreover, the snow depth was significantly (p < 0.05) correlated with the aerosol Fe concentration, confirming the limiting effect of snow/ice cover on the regional dust emission. Given that the Antarctic Peninsula has experienced rapid warming during recent decades, the ice-free areas in the Antarctic Peninsula may act as potential dust sources.

54 ENVIRONMENTAL SCIENCES↗