Article
Geography, Physical
Serena Schroeter, Terence J. O'Kane, Paul A. Sandery
Summary: Across the long-term satellite record of about 43 years, there has been a small overall increase in Antarctic sea ice extent due to opposing regional sea ice concentration anomalies. The long-term trend pattern is mainly influenced by the earliest years of the satellite record, while compensating regional anomalies diminish over time. Recent trends show a reversal of the regional pattern of sea ice behavior, with some regions abruptly shifting in line with recent anomalous sea ice behavior, while other regions exhibit a steady change predating these anomalies. The shifting trend patterns in many regions coincide with enhanced north-south flow and the increasingly wave-3-like structure of the Southern Annular Mode.
Article
Meteorology & Atmospheric Sciences
Gareth J. Marshall, Ryan L. Fogt, John Turner, Kyle R. Clem
Summary: The study demonstrates that ERA5 best reproduces Antarctic near-surface air temperatures in the early period and is also the most homogeneous reanalysis across the early and late periods, indicating a significant change in the relationship between Southern Annular Mode (SAM) and Antarctic near-surface air temperatures between the two periods.
Article
Geosciences, Multidisciplinary
Yue Dong, Lorenzo M. Polvani, David B. Bonan
Summary: Despite global warming, the Southern Ocean has experienced cooling over recent decades. Previous studies have suggested that this cooling is caused by the strengthening of surface winds associated with the positive trend of the Southern Annular Mode. However, our analysis shows that the SAM trend is unlikely to be the main cause of the observed long-term cooling.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Meteorology & Atmospheric Sciences
Morio Nakayama, Hisashi Nakamura, Fumiaki Ogawa
Summary: The study indicates that the midlatitude oceanic frontal zone enhances and anchors the variability of the baroclinic annular mode (BAM) by supplying sensible heat and moisture from the ocean, although the BAM is primarily a manifestation of atmospheric internal dynamics. The BAM modulates momentum flux associated with transient disturbances to induce a modest but robust meridional shift of the polar-front jet, suggesting that it can help maintain the stability of the southern annular mode. The quasi-periodic behavior of the BAM likely reflects the internal dynamics involving atmospheric disturbances on both subweekly and longer time scales.
JOURNAL OF CLIMATE
(2021)
Article
Geosciences, Multidisciplinary
M. Jucker, R. Goyal
Summary: Southern Hemisphere Stratospheric Warming Events (SWEs) are usually associated with a negative phase of the tropospheric Southern Annular Mode (SAM) during the following summer. However, through ensemble climate model simulations, it is shown that these SWEs can cause periods of positive tropospheric SAM in austral spring by increasing lower stratospheric static stability and changing troposphere-to-stratosphere wave propagation. Eventually, the tropospheric SAM switches sign to its negative phase in late spring/early summer due to the downward propagation of the stratospheric signal, which is forced dynamically and radiatively by adiabatic heating and increased shortwave absorption by ozone, respectively.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Meteorology & Atmospheric Sciences
Yusuf A. Bhatti, Laura E. Revell, Adrian J. McDonald
Summary: In this study, anomalies in aerosol loading over the Southern Ocean due to stratospheric ozone depletion were investigated using historical simulations. The results show that the aerosol environment over the Southern Ocean in summertime is no longer representative of pre-ozone hole conditions due to increased marine aerosol fluxes indirectly influenced by stratospheric ozone depletion.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2022)
Article
Multidisciplinary Sciences
Li-Chiao Wang, Yong-Fu Lin, Chau-Ron Wu
Summary: Long-term reanalysis data were used to investigate the inter-decadal to decadal modulations of the North Equatorial Current (NEC) bifurcation in the Pacific after the early 1990s. It was found that the wind stress curl anomaly (WSCA) in the C-BOX region has been remotely modulated by the Southern Annular Mode (SAM) since the early 1990s, leading to a shift in NEC bifurcation towards the equator.
SCIENTIFIC REPORTS
(2022)
Article
Meteorology & Atmospheric Sciences
O. Morgenstern
Summary: The analysis of CMIP6 simulations reveals that the trends in the Southern Annular Mode (SAM) are primarily attributed to ozone depletion, with seasonal variations due to the influences of greenhouse gas increases and stratospheric ozone changes. Models with interactive ozone chemistry show significant differences in attributing SAM changes to these influences compared to models without interactive chemistry.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2021)
Article
Meteorology & Atmospheric Sciences
Dickson Mbigi, Ziniu Xiao
Summary: This study highlights the influence of the Southern Annular Mode (SAM) on East African rainfall, particularly during the October to December period. It reveals a stronger relationship between SAM and rainfall in recent decades compared to earlier years. The study also identifies the mechanisms through which SAM affects rainfall patterns, including the modulation of sea surface temperature anomalies.
JOURNAL OF CLIMATE
(2023)
Article
Meteorology & Atmospheric Sciences
Fei Zheng, Xiaoning Liu, Hao Wang, Yuxun Li, Rui Wang, Shuailei Yao, Wenjie Dong
Summary: The Southern Hemisphere Annular Mode (SAM), the dominant mode of atmospheric circulation in the Southern Hemisphere, has shown changes in its seasonal trend in relation to ozone recovery. The summer SAM trend has decreased since 2001, reducing the seasonal difference with winter, while the winter SAM has shown an increasing positive trend in the early 21st century, reversing the previous seasonality. The winter SAM changes are found to be part of a multidecadal oscillation, possibly originating from the Atlantic Multidecadal Oscillation.
INTERNATIONAL JOURNAL OF CLIMATOLOGY
(2023)
Article
Geosciences, Multidisciplinary
Ewa M. Bednarz, Daniele Visioni, Jadwiga H. Richter, Amy H. Butler, Douglas G. MacMartin
Summary: The study analyzes the impacts of Stratospheric Aerosol Injection (SAI) strategies on the Southern Annular Mode (SAM) using the Community Earth System Model. The results show that the SAM response is primarily dependent on the latitude of injection, with northern and equatorial injections driving a positive phase of SAM and southern injections driving a negative phase of SAM.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Multidisciplinary Sciences
Jonathan King, Kevin J. Anchukaitis, Kathryn Allen, Tessa Vance, Amy Hessl
Summary: This study uses data assimilation to reconstruct the Southern Annular Mode over the last 2000 years and finds that its history reflects natural climate variability, except for the most-recent positive trend. The Southern Annular Mode is the leading mode of atmospheric variability in the extratropical Southern Hemisphere and has wide-ranging effects on ecosystems and societies. The study also suggests that the modern positive trend of the Southern Annular Mode is likely a response to anthropogenic climate change.
NATURE COMMUNICATIONS
(2023)
Article
Geosciences, Multidisciplinary
F. Robertson, L. E. Revell, H. Douglas, A. T. Archibald, O. Morgenstern, D. Frame
Summary: The year when total column ozone (TCO) returns to 1980 levels is commonly used to measure recovery from ozone-depleting substances. However, this metric fails to account for internal variability and the timing of significant TCO losses. Using the signal-to-noise (S/N) metric, this study investigates how TCO can return to pre-disturbance conditions. The findings suggest that TCO de-emerges before returning to its 1980 value, making S/N a suitable metric for determining TCO recovery.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Meteorology & Atmospheric Sciences
Fraser Dennison, Matthew T. T. Woodhouse
Summary: Chemistry-climate models are important for predicting climate change. This study evaluates the ACCESS-CM2-Chem model and finds that its simulation of stratospheric ozone is significantly improved compared to its predecessor. The model performs well in simulating the trend of summertime SAM and shows sensitivity to changes in ozone depletion forcing.
JOURNAL OF SOUTHERN HEMISPHERE EARTH SYSTEMS SCIENCE
(2023)
Article
Meteorology & Atmospheric Sciences
Dickson Mbigi, Ziniu Xiao
Summary: This study investigates the relationship between the Southern Annular Mode (SAM) and the rainfall variability in northern Australia. The results show a significant negative correlation between the SAM and the subsequent rainfall in northern Australia. Further analysis reveals that the SAM can trigger sea surface temperature anomalies in the southern Indian Ocean through air-sea interactions, which impact the rainfall patterns in northern Australia.
Article
Meteorology & Atmospheric Sciences
Ryan L. Fogt, Connor P. Belak, Julie M. Jones, Laura C. Slivinski, Gilbert P. Compo
Summary: This study compares gridded seasonal pressure reconstructions with other datasets, historical data, and ship records to evaluate their skill and performance in the early 20th century. The findings show that the reconstruction uncertainty over the Southern Ocean in the early 20th century is around 2-4 hPa, and despite challenges in certain areas, aspects of the interannual variability are often captured by the reconstructions. Additional comparisons with 20th-century reanalysis products demonstrate the value of assimilating historical observations in reducing ensemble spread and aligning with reconstructions and observational uncertainty.
INTERNATIONAL JOURNAL OF CLIMATOLOGY
(2021)
Correction
Environmental Sciences
Kyle R. Clem, Ryan L. Fogt, John Turner, Benjamin R. Lintner, Gareth J. Marshall, James R. Miller, James A. Renwick
NATURE CLIMATE CHANGE
(2021)
Article
Environmental Sciences
N. Shabanov, G. J. Marshall, W. G. Rees, S. A. Bartalev, O. Tutubalina, E. Golubeva
Summary: This study examines the response of Arctic vegetation to temperature changes, finding that seasonal trends cannot fully capture complex interannual variations. Green-up and senescence trends exhibit different characteristics over the growing season, with the intensity and timing of changes dependent on vegetation type. Further release of climatic constraints is likely to impact both the environment and vegetation, leading to shifts in LAI seasonal amplitudes.
ENVIRONMENTAL RESEARCH LETTERS
(2021)
Article
Environmental Sciences
Ryan L. Fogt, Amanda M. Sleinkofer, Marilyn N. Raphael, Mark S. Handcock
Summary: In contrast to the Arctic, there has been a significant increase in Antarctic sea ice extent since 1979. However, the short and highly variable nature of observed Antarctic sea ice extent limits our understanding of its historical context. Through reconstructions, it has been found that the period since 1979 is the only time when all four seasons show a significant increase in Antarctic sea ice, with significant decreases in the early and middle twentieth century. These reconstructions provide reliable estimates of seasonally resolved Antarctic sea ice extent and can improve our understanding of air-sea-ice interactions in the Antarctic climate system.
NATURE CLIMATE CHANGE
(2022)
Article
Meteorology & Atmospheric Sciences
Gareth J. Marshall, Ryan L. Fogt, John Turner, Kyle R. Clem
Summary: The study demonstrates that ERA5 best reproduces Antarctic near-surface air temperatures in the early period and is also the most homogeneous reanalysis across the early and late periods, indicating a significant change in the relationship between Southern Annular Mode (SAM) and Antarctic near-surface air temperatures between the two periods.
Article
Geosciences, Multidisciplinary
John Turner, Caroline Holmes, Thomas Caton Harrison, Tony Phillips, Babula Jena, Tylei Reeves-Francois, Ryan Fogt, Elizabeth R. Thomas, C. C. Bajish
Summary: On February 25, 2022, Antarctic sea ice extent reached a satellite-era record low level, and sea ice anomalies were observed in all sectors of the Southern Ocean, with the largest anomalies in the Ross and Weddell Seas.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Oceanography
John C. King, Gareth J. Marshall, Steve Colwell, Stefanie Arndt, Clare Allen-Sader, Tony Phillips
Summary: This study evaluates the performance of the ERA-Interim and ERA5 atmospheric reanalyses over the Weddell Sea ice zone using measurements from drifting buoys. Both reanalyses capture the temporal variability in surface pressure and near-surface air temperature well, but exhibit a warm bias relative to the buoy measurements. The wind speed biases are small, while the biases in downwelling shortwave and longwave radiation are significant. Overall, both reanalyses reproduce the buoy measurements within the limits of measurement uncertainty, except for near-surface temperature.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
(2022)
Correction
Environmental Sciences
Kyle R. Clem, Ryan L. Fogt, John Turner, Benjamin R. Lintner, Gareth J. Marshall, James R. Miller, James A. Renwick
NATURE CLIMATE CHANGE
(2023)
Article
Meteorology & Atmospheric Sciences
Hua Lu, Steve Cowell, John King, Andrew Orr, Tony Phillips, Emilia Dobb, Jonathan Xue, Sabina Kucieba, Guy Phillips, Gareth Marshall
Summary: This study compares the near-surface air temperatures at Signy Station with nearby Orcadas station and reanalysis datasets to provide a more comprehensive understanding of weather and climate variability in the South Orkney Islands. The study also examines temperature trends in relation to changes in large-scale circulation and sea surface temperature.
INTERNATIONAL JOURNAL OF CLIMATOLOGY
(2023)
Review
Environmental Sciences
Xichen Li, Wenju Cai, Gerald A. Meehl, Dake Chen, Xiaojun Yuan, Marilyn Raphael, David M. Holland, Qinghua Ding, Ryan L. Fogt, Bradley R. Markle, Guojian Wang, David H. Bromwich, John Turner, Shang-Ping Xie, Eric J. Steig, Sarah T. Gille, Cunde Xiao, Bingyi Wu, Matthew A. Lazzara, Xianyao Chen, Sharon Stammerjohn, Paul R. Holland, Marika M. Holland, Xiao Cheng, Stephen F. Price, Zhaomin Wang, Cecilia M. Bitz, Jiuxin Shi, Edwin P. Gerber, Xi Liang, Hugues Goosse, Changhyun Yoo, Minghu Ding, Lei Geng, Meijiao Xin, Chuanjin Li, Tingfeng Dou, Chengyan Liu, Weijun Sun, Xinyue Wang, Chentao Song
Summary: A substantial climatic changes have been observed in the Antarctic over the modern satellite era, many of which are believed to be influenced by tropical-polar teleconnections through Rossby wave dynamics. These connections play a significant role in shaping Antarctic climate variability and changes in recent years.
NATURE REVIEWS EARTH & ENVIRONMENT
(2021)
Article
Meteorology & Atmospheric Sciences
Ryan L. Fogt, Charlotte J. Connolly
Summary: This study analyzes the spatial pattern of pressure variability across the Southern Hemisphere in the early twentieth century, revealing synchronous but opposite-signed pressure relationships between Antarctica and the midlatitudes in the Southern Hemisphere, especially in the summer and autumn. In addition to connections with the southern annular mode, regional and shorter duration pressure trends are found to be associated with influences from tropical variability and potentially the zonal wavenumber 3 pattern.
JOURNAL OF CLIMATE
(2021)
