Climate Change In Antarctica Research Articles

The role of ice-sheet dynamics in the Miocene-Pliocene depositional systems of the Ross Sea, Antarctica

The dynamics of the Antarctic ice sheet (AIS) have profound implications for the evolution of the Antarctic continental margin, global ocean currents, and climate changes. Marine sediments from the Antarctic continental margins recorded the history of the advance and retreat of the AIS. In this study, we present an integrated analysis of the sedimentary characteristics of the Early Miocene to Late Miocene of the Ross Sea by using 2D seismic reflection data and cores from International Ocean Discovery Program (IODP) Expedition 374 Sites U1521, U1522, and U1524. The characteristics of the seismic facies and sediments show that the expansion and grounding of the ice sheets across the continental shelf significantly influenced the depositional processes, leading to increased glacial erosion, the formation of prograding wedges, mass transport deposits (MTDs), and mixed (turbidite-contourite) depositional systems since the Early Miocene. The seaward migration of the continental shelf edge and the steepening of the continental slope were mainly influenced by the glaciation of extreme expansion of the AIS. Marked increases in the prograding wedge and MTD are associated with extensive sediment reworking and deposition at the grounding zones and along the continental slope as a result of ice sheet expansion. The development of the mixed (turbidite-contourite) depositional systems was the result of extensive sediment reworking and deposition by gravity flows and bottom currents on the continental slope and the rise. This research provides new insights into the complexity of the ice sheet and the sensibility of marginal sediments in responding to the past climate changes in Antarctica.

The quandary of detecting the signature of climate change in Antarctica

The quandary of detecting the signature of climate change in Antarctica

Advancing Antarctic climate change policy: upcoming opportunities for scientists and policymakers to work together

AbstractClimate change is increasingly affecting Antarctica and the rest of the world. Urgent policy responses are needed to mitigate its associated impacts. Engagement of the Antarctic Treaty Consultative Meeting (ATCM), Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) and Committee for Environmental Protection (CEP) with the issue of climate change has culminated in several important meetings planned for 2023/2024. Researchers play a crucial role in the provision of the best available science to inform action by Antarctic policymakers, and the Scientific Committee on Antarctic Research (SCAR) clearly will play an important role in representing the Antarctic science community and delivering the latest science into the upcoming meetings. However, recognizing the ATCM's call for Parties and other stakeholders to bring experts to its meeting to support the work and with acknowledgement by CCAMLR and CEP of the value of including a range of scientific experts, we highlight the opportunity for and importance of researchers engaging proactively to offer further bespoke scientific support. Given the urgency of addressing climate change in Antarctica and beyond, every effort is needed from researchers and policymakers to work together to facilitate the necessary policy responses at both the national and international level.

Observation of the low-altitude cloud characteristics with Mie scattering Lidar at the Great Wall Station, Antarctica

The observation of polar clouds is of great significance to studying climate change in Antarctica. The modified Klett–Fernald method and Mie scattering light detection and ranging (Lidar) were used to study the characteristics of low-altitude clouds from February 15 to March 2, 2017 at the Great Wall Station. The temporal and spatial variations in the cloud extinction coefficient were obtained, and the optical and physical characteristics of the low-altitude clouds were statistically analyzed. The analysis shows that the near-ground atmosphere is very clean and the atmosphere at low heights is covered by low-altitude clouds. The meteorological and Lidar data show that the polar cyclone may be the main driving force of the cloud-height changes at this station.

Ice matters: Life-history strategies of two Antarctic seals dictate climate change eventualities in the Weddell Sea.

The impacts of climate change in Antarctica and the Southern Ocean are not uniform and ice‐obligate species with dissimilar life‐history characteristics will likely respond differently to their changing ecosystems. We use a unique data set of Weddell Leptonychotes weddellii and crabeater seals' (CESs) Lobodon carcinophaga breeding season distribution in the Weddell Sea, determined from satellite imagery. We contrast the theoretical climate impacts on both ice‐obligate predators who differ in life‐history characteristics: CESs are highly specialized Antarctic krill Euphausia superba predators and breed in the seasonal pack ice; Weddell seals (WESs) are generalist predators and breed on comparatively stable fast ice. We used presence–absence data and a suite of remotely sensed environmental variables to build habitat models. Each of the environmental predictors is multiplied by a ‘climate change score’ based on known responses to climate change to create a ‘change importance product’. Results show CESs are more sensitive to climate change than WESs. Crabeater seals prefer to breed close to krill, and the compounding effects of changing sea ice concentrations and sea surface temperatures, the proximity to krill and abundance of stable breeding ice, can influence their post‐breeding foraging success and ultimately their future breeding success. But in contrast to the Ross Sea, here WESs prefer to breed closer to larger colonies of emperor penguins (Aptenodytes forsteri). This suggests that the Weddell Sea may currently be prey‐abundant, allowing the only two air‐breathing Antarctic silverfish predators (Pleuragramma antarctica) (WESs and emperor penguins) to breed closer to each other. This is the first basin‐scale, region‐specific comparison of breeding season habitat in these two key Antarctic predators based on real‐world data to compare climate change responses. This work shows that broad‐brush, basin‐scale approaches to understanding species‐specific responses to climate change are not always appropriate, and regional models are needed—especially when designing marine protected areas.

Epiphytic diatom community structure and richness is determined by macroalgal host and location in the South Shetland Islands (Antarctica).

The marine waters around the South Shetland Islands are paramount in the primary production of this Antarctic ecosystem. With the increasing effects of climate change and the annual retreat of the ice shelf, the importance of macroalgae and their diatom epiphytes in primary production also increases. The relationships and interactions between these organisms have scarcely been studied in Antarctica, and even less in the volcanic ecosystem of Deception Island, which can be seen as a natural proxy of climate change in Antarctica because of its vulcanism, and the open marine system of Livingston Island. In this study we investigated the composition of the diatom communities in the context of their macroalgal hosts and different environmental factors. We used a non-acidic method for diatom digestion, followed by slidescanning and diatom identification by manual annotation through a web-browser-based image annotation platform. Epiphytic diatom species richness was higher on Deception Island as a whole, whereas individual macroalgal specimens harboured richer diatom assemblages on Livingston Island. We hypothesize this a possible result of a higher diversity of ecological niches in the unique volcanic environment of Deception Island. Overall, our study revealed higher species richness and diversity than previous studies of macroalgae-inhabiting diatoms in Antarctica, which could however be the result of the different preparation methodologies used in the different studies, rather than an indication of a higher species richness on Deception Island and Livingston Island than other Antarctic localities.

Monthly Variation in the Macromolecular Composition of Phytoplankton Communities at Jang Bogo Station, Terra Nova Bay, Ross Sea.

Organic carbon fixed by photosynthesis of phytoplankton during the polar growing period could be important for their survival and consumers during the long polar night. Differences in biochemical traits of phytoplankton between ice-free and polar night periods were investigated in biweekly water samples obtained at the Korean “Jang Bogo Station” located in Terra Nova Bay, Antarctica. The average concentration of total Chl-a from phytoplankton dominated by micro-sized species from the entire sampling period was 0.32 μg L–1 (SD = ± 0.88 μg L–1), with the highest concentration of 4.29 μg L–1 in February and the lowest concentration of 0.01 μg L–1 during the ice-covered polar night (April–October) in 2015. The highest protein concentration coincided with the peak Chl-a concentration in February and decreased rapidly relative to the carbohydrate and lipid concentrations in the early part of polar night. Among the different biochemical components, carbohydrates were the predominant constituent, accounting for 69% (SD = ± 14%) of the total particulate organic matter (POM) during the entire study period. The carbohydrate contributions to the total POM markedly increased from 39 ± 8% during the ice-free period to 73 ± 9% during the polar night period. In comparison, while we found a significant negative correlation (r2 = 0.92, p < 0.01) between protein contributions and carbohydrate contributions, lipid contributions did not show any particular trend with relatively small temporal variations during the entire observation period. The substantial decrease in the average weight ratio of proteins to carbohydrates from the ice-free period (mean ± SD = 1.0 ± 0.3) to the ice-covered period (mean ± SD = 0.1 ± 0.1) indicates a preferential loss of nitrogen-based proteins compared to carbohydrates during the polar night period. Overall, the average food material (FM) concentration and calorific contents of FM in this study were within the range reported previously from the Southern Ocean. The results from this study may serve as important background data for long-term monitoring of the regional and interannual variations in the physiological state and biochemical compositions of phytoplankton resulting from future climate change in Antarctica.

An Assessment of ERA5 Reanalysis for Antarctic Near-Surface Air Temperature

The European Center for Medium-Range Weather Forecasts (ECMWF) released its latest reanalysis dataset named ERA5 in 2017. To assess the performance of ERA5 in Antarctica, we compare the near-surface temperature data from ERA5 and ERA-Interim with the measured data from 41 weather stations. ERA5 has a strong linear relationship with monthly observations, and the statistical significant correlation coefficients (p &lt; 0.05) are higher than 0.95 at all stations selected. The performance of ERA5 shows regional differences, and the correlations are high in West Antarctica and low in East Antarctica. Compared with ERA5, ERA-Interim has a slightly higher linear relationship with observations in the Antarctic Peninsula. ERA5 agrees well with the temperature observations in austral spring, with significant correlation coefficients higher than 0.90 and bias lower than 0.70 °C. The temperature trend from ERA5 is consistent with that from observations, in which a cooling trend dominates East Antarctica and West Antarctica, while a warming trend exists in the Antarctic Peninsula except during austral summer. Generally, ERA5 can effectively represent the temperature changes in Antarctica and its three subregions. Although ERA5 has bias, ERA5 can play an important role as a powerful tool to explore the climate change in Antarctica with sparse in situ observations.

Coastal Bacterial Community Response to Glacier Melting in the Western Antarctic Peninsula.

Current warming in the Western Antarctic Peninsula (WAP) has multiple effects on the marine ecosystem, modifying the trophic web and the nutrient regime. In this study, the effect of decreased surface salinity on the marine microbial community as a consequence of freshening from nearby glaciers was investigated in Chile Bay, Greenwich Island, WAP. In the summer of 2016, samples were collected from glacier ice and transects along the bay for 16S rRNA gene sequencing, while in situ dilution experiments were conducted and analyzed using 16S rRNA gene sequencing and metatranscriptomic analysis. The results reveal that certain common seawater genera, such as Polaribacter, Pseudoalteromonas and HTCC2207, responded positively to decreased salinity in both the bay transect and experiments. The relative abundance of these bacteria slightly decreased, but their functional activity was maintained and increased the over time in the dilution experiments. However, while ice bacteria, such as Flavobacterium and Polaromonas, tolerated the increased salinity after mixing with seawater, their gene expression decreased considerably. We suggest that these bacterial taxa could be defined as sentinels of freshening events in the Antarctic coastal system. Furthermore, these results suggest that a significant portion of the microbial community is resilient and can adapt to disturbances, such as freshening due to the warming effect of climate change in Antarctica.

Antarctic krill fishery effects over penguin populations under adverse climate conditions: Implications for the management of fishing practices.

Fast climate changes in the western Antarctic Peninsula are reducing krill density, which along with increased fishing activities in recent decades, may have had synergistic effects on penguin populations. We tested that assumption by crossing data on fishing activities and Southern Annular Mode (an indicator of climate change in Antarctica) with penguin population data. Increases in fishing catch during the non-breeding period were likely to result in impacts on both chinstrap (Pygoscelis antarcticus) and gentoo (P. papua) populations. Catches and climate change together elevated the probability of negative population growth rates: very high fishing catch on years with warm winters and low sea ice (associated with negative Southern Annular Mode values) implied a decrease in population size in the following year. The current management of krill fishery in the Southern Ocean takes into account an arbitrary and fixed catch limit that does not reflect the variability of the krill population under effects of climate change, therefore affecting penguin populations when the environmental conditions were not favorable.

Enhanced westerlies drove penguin movement at 1000 yr BP on Ardley Island, west Antarctic Peninsula

Understanding responses by penguins to climate change in Antarctica is often complicated by other factors including microclimate and landscape effects. Here, we analyze an ornithogenic sediment profile to reconstruct penguin occupation history on the eastern side of Ardley Island, west Antarctic Peninsula, and synthesize the results from various studies on Ardley Island in the past 20 years. Penguins have inhabited the eastern side of this island since about 900 yr BP, with populations significantly increasing from ∼500 yr BP. On the western side, delineated by the Ardley Ridge Line, penguins began to abandon nest or molt sites at ∼1000 yr BP. By the time of 500 yr BP, the abandonment and population decline became a common tendency on the west side. This shift in occupation areas was likely driven by local microclimate and a change in wind patterns causing more snow to accumulate on the west side of the island. We found a linkage between this penguin movement and the Southern Westerly Winds, which became stronger at ∼1000 yr BP and impacted local conditions at Ardley Island, likely induced by more positive Southern Annular Mode (SAM). These results indicate that island topography, wind and snow patterns, combined with large-scale climate forcing can be just as important in determining penguin distribution as temperature and other environmental factors. This study provides a new perspective for investigating the possible impact of microclimate and site topography on penguin behavior.

Analysis of the temporal–spatial changes in surface radiation budget over the Antarctic sea ice region

The surface radiation budget (SRB) of the Antarctic sea ice region (ASIR) is important for the climate change in Antarctica, which partly explains the global warming. Long-term (1982–2015) satellite-derived (EUMETSAT Satellite Application Facility on Climate Monitoring, CLARA-A2) and reanalysis (European Centre for Medium-Range Weather Forecasts, ERA-Interim) datasets provided high quality and global coverage surface radiation products, which enabled us to quantify the SRB of the ASIR and widen our understanding of the polar climate. The downwelling longwave (LW) and shortwave (SW) radiation from the two datasets were validated at two Baseline Surface Radiation Network Stations (i.e., Neumayer and Syowa). Cloud LW emission dominated over cloud SW reflection and absorption due to high-albedo over the sea ice surface, thereby leading to a positive all-wave cloud radiative forcing (CRF) within 0–100 W m−2. This result indicated a warming effect on the surface of the ASIR, except during the austral summer. Compared with the all sky, substantial solar radiation was absorbed by the surface which under the clear sky will result in the increasing of temperature and sea ice melting during the austral summer; hence, the SW CRF had a major influence on all-wave CRF and caused more than −150 W m−2 of cooling near the edge of the sea ice. The summer averages of all-wave CRF over the ASIR surface were − 43.02 and − 35.74 W m−2 for the ERA-Interim and CLARA-A2 datasets, respectively. Contrary to the effect of CRF, the surface net LW radiation (LWnet) exhibited a cooling effect over the ASIR surface throughout the year and peaks at −47.21 W m−2 for CLARA-A2 dataset in December. Meanwhile, a warming effect was caused by the surface net SW radiation (SWnet) peaks at 101.52 and 104.09 W m−2 for the ERA-Interim and CLARA-A2 datasets, respectively. In summer, the warming effect caused by the surface net all-wave radiation in East Antarctica was deeper than that in West Antarctica. The time series and trend analysis showed that the surface net radiation and CRF over the entire ASIR basically exhibited a decreasing trend. The descending speed of SWnet (−3.652 W m−2 decade−1) about five times faster than that of LWnet (−0.722 W m−2 decade−1). Although a significant trough appeared in 1993/1994 of the time series curves of All-wave CRF, it had a deeply negative trend with about −3.443 W m−2 decade−1. Detailed analysis on the five longitudinal sectors around Antarctica (the Weddell Sea, the Indian Ocean, the Pacific Ocean, the Ross Sea, and the Bellingshausen-Amundsen Sea) can further help us understand the SRB of the ASIR.

Coastal Ecosystem Contamination by Heavy Metals as an Indicator of Climate Change in Antarctica

Coastal Ecosystem Contamination by Heavy Metals as an Indicator of Climate Change in Antarctica

Effects of temperature and water availability on light energy utilization in photosynthetic processes of Deschampsia antarctica.

Regional climate change in Antarctica would favor the carbon assimilation of Antarctic vascular plants, since rising temperatures are approaching their photosynthetic optimum (10-19°C). This could be detrimental for photoprotection mechanisms, mainly those associated with thermal dissipation, making plants more susceptible to eventual drought predicted by climate change models. With the purpose to study the effect of temperature and water availability on light energy utilization and putative adjustments in photoprotective mechanisms of Deschampsia antarctica Desv., plants were collected from two Antarctic provenances: King George Island and Lagotellerie Island. Plants were cultivated at 5, 10 and 16°C under well-watered (WW) and water-deficit (WD, at 35% of the field capacity) conditions. Chlorophyll fluorescence, pigment content and de-epoxidation state were evaluated. Regardless of provenances, D. antarctica showed similar morphological, biochemical and functional responses to growth temperature. Higher temperature triggered an increase in photochemical activity (i.e. electron transport rate and photochemical quenching), and a decrease in thermal dissipation capacity (i.e. lower xanthophyll pool, Chl a/b and β carotene/neoxanthin ratios). Leaf mass per unit area was reduced at higher temperature, and was only affected in plants exposed to WD at 16°C and exhibiting lower electron transport rate and amount of chlorophylls. D. antarctica is adapted to frequent freezing events, which may induce a form of physiological water stress. Photoprotective responses observed under WD contribute to maintain a stable photochemical activity. Thus, it is possible that short-term temperature increases could favor the photochemical activity of this species. However, long-term effects will depend on the magnitude of changes and the plant's ability to adjust to new growth temperature.

Testing reanalysis data sets in Antarctica: Trends, persistence properties, and trend significance

AbstractThe reanalysis data sets provide important sources for investigating the climate in Antarctica where stations are sparse. In this paper, we compare the 2 m near‐surface temperature data from five major reanalysis data sets with observational Antarctic stations data over the last 36 years: (i) the National Centers for Environmental Prediction and the National Center for Atmospheric Research Reanalysis (NCEP1), (ii) NCEP‐DOE Reanalysis 2 (NCEP2), (iii) the European Centre for Medium‐Range Weather Forecasts Interim Reanalysis (ERA‐Interim), (iv) the Japanese 55 year Reanalysis (JRA‐55), and (v) the National Aeronautics and Space Administration Modern‐Era Retrospective‐analysis for Research and Applications. In our assessment, we compare (a) the annual and seasonal trends obtained by linear regression analysis, (b) the standard deviation around the annual trends, (c) the detrended lag‐1‐autocorrelation C(1), (d) the Hurst exponent α that characterizes the long‐term memory in a record, and (e) the significance levels of the warming/cooling trends. We find that all five reanalysis data sets are able to reproduce quite well the long‐term memory in the instrumental data. In contrast, C(1), which is needed as input for the conventional significance analysis, shows fully erratic behavior. The observational warming/cooling trends in East and West Antarctica are not reproduced well by all reanalysis data sets, in particular, NCEP1, NCEP2, and JRA‐55 show spurious warming trends in many parts of East Antarctica, even in those parts where cooling has been observed. In contrast, the standard deviation around the trends is quite well reproduced by all reanalysis data sets. In the peninsula where the station density is quite high, the performance of the reanalysis data is considerably better. It is remarkable that all reanalysis data sets as well as the observational data show (under the assumption of a long‐term persistent process) that in the considered time period since 1979 the warming in the peninsula is not significant with p values well above 0.1.

Projected asymmetric response of Adélie penguins to Antarctic climate change.

The contribution of climate change to shifts in a species’ geographic distribution is a critical and often unresolved ecological question. Climate change in Antarctica is asymmetric, with cooling in parts of the continent and warming along the West Antarctic Peninsula (WAP). The Adélie penguin (Pygoscelis adeliae) is a circumpolar meso-predator exposed to the full range of Antarctic climate and is undergoing dramatic population shifts coincident with climate change. We used true presence-absence data on Adélie penguin breeding colonies to estimate past and future changes in habitat suitability during the chick-rearing period based on historic satellite observations and future climate model projections. During the contemporary period, declining Adélie penguin populations experienced more years with warm sea surface temperature compared to populations that are increasing. Based on this relationship, we project that one-third of current Adélie penguin colonies, representing ~20% of their current population, may be in decline by 2060. However, climate model projections suggest refugia may exist in continental Antarctica beyond 2099, buffering species-wide declines. Climate change impacts on penguins in the Antarctic will likely be highly site specific based on regional climate trends, and a southward contraction in the range of Adélie penguins is likely over the next century.

Potential for Southern Hemisphere climate surprises

ABSTRACTClimate model results suggest that future climate change in Antarctica will be accompanied by continued strengthening and poleward contraction of the Southern Ocean westerly wind belt. Paleoclimate records suggest past changes in the westerly winds can be abrupt and that healing of the Antarctic ozone hole could lead to poleward contraction of the westerlies and increased meridional atmospheric transport of warm air regionally into Antarctica. An abrupt shift to more meridional circulation could lead to notable changes in moisture availability for extra‐Antarctic regions, increased Antarctic ice sheet disintegration and more rapid sea‐level rise.

Environmental and climate changes in Antarctica in the Geological Past

In the Cretaceous time, Antarctica was characterized by subtropical and tropical climate. The Early Eocene was warmest in the Antarctic history but this Climatic Optimum terminated with a long-term cooling trend that culminated in continental-scale glaciation of Antarctica at about 34 Ma ago. There is indirect evidence that small ice caps developed within central Antarctica in the Late Eocene (42−34 Ma). From the Early Oligocene to the Middle Miocene (34−13 Ma) ice sheet was wet-based and fluctuated considerably in volume, but about 14 m.y. ago it became dry-based and more stable. Seismic data collected on the East Antarctic margin give valuable information on dynamics of the past ice sheets. These data shows that the sedimentary cover of the western Wilkes Land margin includes a giant (c. 200 000 km 2 ) deep-water fan which formed between c. 43 and 34 Ma ago. The average rate of sedimentation in the central part of fan was 230–250 m/m.y. Active input of terrigenous sediments into deep-water denotes high-energy fluvial system within the Wilkes Land. Emergence of this fluvial system evidences earliest glaciation in the Antarctic interior which fed full-flowing rivers. The thickness of strata deposited during post-Early Oligocene glaciations on the Antarctic margin generally reflects the averaged energy of depositional environments. The thickest sediments (up to 2.0 km, i.e. almost twice more than in other parts of East Antarctic margin) and inferred highest energy are seen in the central Cooperation Sea, on the central Wilkes Land margin and in the D'Urville Sea. The areas with the thickest post-Early Oligocene strata correlate with places where present-day ice discharge is highest, such as via the Lambert, Totten and Mertz/Ninnis Glaciers. The correlation points to high ice (and sediment) flux in the same areas since the Early Oligocene.

Mycothalli of the hepatic Barbilophozia hatcheri in Antarctica: distribution and identities of mycobionts

Forty-four herbarium specimens of the hepatic Barbilophozia hatcheri, collected from across the entire range of the species in Antarctica (54–68 °S), were examined for fungal colonisation. Mycothalli, consisting of hyaline hyphae in rhizoids or hyphal coils in rhizoid bases and stem medullary cells, were present in 42 specimens. The frequencies of mycothalli declined at higher latitudes and were associated positively with annual air temperatures. In contrast, the frequency of dark septate hyphae on stems increased at higher latitudes. Sequencing of ITS regions of fungal rRNA genes amplified from B. hatcheri from 54 °S, 61 °S and 68 °S indicated that Cladophialophora species colonised plants at higher latitudes, but that most fungi had >99 % homology with members of Sebacinales clade B, with best matches to mycobionts of B. lycopodioides, Lophoziopsis excisa and Protolophozia crispata. We propose the use of herbarium specimens of mycothalli as proxies for climate change in Antarctica.

Загрязненность прибрежной экосистемы тяжелыми металлами как показатель климатических изменений в Антарктике

Загрязненность прибрежной экосистемы тяжелыми металлами как показатель климатических изменений в Антарктике