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Antarctic Climate Change in the 21st Century (AntClim21)

AntClim21 documents:

 

Recent committee publications:

Ice core and climate reanalysis analogs to predict Antarctic and Southern Hemisphere climate changes Mayewski, P.A., A.M., Carleton, S.D. Birkel, D. Dixon, A.V. Kurbatov, E. Korotkikh, J. McConnell, M. Curran, J. Cole-Dai, S. Jiang, C. Plummer, T. Vance, K.A. Maasch, S.B. Sneed, M/ Handley, 2016: Ice core and climate reanalysis analogs to predict Antarctic Southern Hemisphere Climate Changes, Quaternary Science Reviews.

Potential for Southern Hemisphere Climate Surprises Mayewski, P.A., T. Bracegirdle, I. Goodwin, D. Schneider, N.A.N. Bertler, S. Birkel, A. Carleton, M. H. England, J-H. Kang, A. Khan, J. Russell, J. Turner and I. Veliconga, 2015: Potential for Southern Hemisphere climate surprises, Quaternary Science.

A Multi-Disciplinary Perspective on Climate Model Evaluation For Antarctica Bracegirdle, T., N. Bertler, A. Carleton, Q. Ding, C. Fogwill, J. Fyfe, H. Hellmer, A.Karpechko, K. Kusahara, E. Larour, P. Mayewski, W. Meier, L. Polvani, J.Russell, S. Stevenson, J. Turner, J. van Wessem, W. van de Berg, and I. Wainer, 2015: A MULTI-DISCIPLINARY PERSPECTIVE ON CLIMATE MODEL EVALUATION FOR ANTARCTICA. Bull. Amer. Meteor. Soc. doi:10.1175/BAMSD-15-00108.1.

AntClim21 reports:

 

Publication highlights:

Dissolved black carbon in Antarctic lakes: Chemical signatures of past and present sources: This publication was led by Dr. Alia Khan, APECS Representative to the AntClim21 Steering Committee and recent graduate from the Institute of Arctic and Alpine Resaerch at the University of Colorado - Boulder. Abstract: The perennially ice-covered, closed-basin lakes in the McMurdo Dry Valleys, Antarctica, serve as sentinels for understanding the fate of dissolved black carbon from glacial sources in aquatic ecosystems. Here we show that dissolved black carbon can persist in freshwater and saline surface waters for thousands of years, while preserving the chemical signature of the original source materials. The ancient brines of the lake bottom waters have retained dissolved black carbon with a woody chemical signature, representing long-range transport of black carbon from wildfires. In contrast, the surface waters are enriched in contemporary black carbon from fossil fuel combustion. Comparison of samples collected 25 years apart from the same lake suggests that the enrichment in anthropogenic black carbon is recent. Differences in the chemical composition of dissolved black carbon among the lakes are likely due to biogeochemical processing such as photochemical degradation and sorption on metal oxides.

Khan, A. L., R. Jaffé, Y. Ding, and D. M. McKnight (2016), Dissolved black carbon in Antarctic lakes: Chemical signatures of past and present sources, Geophys. Res. Lett., 43, 5750–5757, doi:10.1002/2016GL068609.

The Importance of sea ice area biases in 21st century multimodel projections of Antarctic temperature and precipitation:  This publication is led by Dr. Thomas Bracegirdle from the AntClim21 steering committee and the Brittish Antarctic Survey.  Abstract: Climate models exhibit large biases in sea ice area (SIA) in their historical simulations. This study explores the impacts of these biases on multimodel uncertainty in Coupled Model Intercomparison Project phase 5 (CMIP5) ensemble projections of 21st century change in Antarctic surface temperature, net precipitation, and SIA. The analysis is based on time slice climatologies in the Representative Concentration Pathway 8.5 future scenario (2070–2099) and historical (1970–1999) simulations across 37 different CMIP5 models. Projected changes in net precipitation, temperature, and SIA are found to be strongly associated with simulated historical mean SIA (e.g., cross-model correlations of r = 0.77, 0.71, and −0.85, respectively). Furthermore, historical SIA bias is found to have a large impact on the simulated ratio between net precipitation response and temperature response. This ratio is smaller in models with smaller-than-observed SIA. These strong emergent relationships on SIA bias could, if found to be physically robust, be exploited to give more precise climate projections for Antarctica.  Bracegirdle, T.J., Stephensn, D.B., Turner, J., and Phillips, T. 

The Southern Ocean ecosystem under multiple climate change stresses - an integrated circumpolar assessment: This publication is a collaboration between Ant-ERA and AntClim21, led by Julian Gutt providing the first quantitative assessment effects on the Antarctic / Southern Ocean marine ecosystem from observed and projected environmental change. The compiled data sets suggests that The areas affected by environmental stressors range from 33% of the SO for a single stressor, 11% for two and 2% for three, to <1% for four and five overlapping factors. In the future, areas expected to be affected by 2 and 3 overlapping factors are equally large, including potential iceberg changes, and together cover almost 86% of the SO ecosystem.  Gutt, J., Bertler, N., Bracegirdle, T. J., Buschmann, A., Comiso, J., Hosie, G., Isla, E., Schloss, I. R., Smith, C. R., Tournadre, J. and Xavier, J. C. (2015), The Southern Ocean ecosystem under multiple climate change stresses - an integrated circumpolar assessment. Global Change Biology. doi: 10.1111/gcb.12794

Mineral Dust Variability in Antarctic Ice for Different Climate Change Conditions: A large decrease in dust concentration and a small increase in dust size was noted during the transition from the last glacial to the Holocene (T1). Seasonal variability of dust concentration, dust size, and the glacial’s phase-lag enabled the derivation of a significant pairing of transport and intensified source during this time.  However, this trend vanished during the Holocene. The driving cause for the increased dust deposition in Antarctica for all previous interglacial time slices compared to the pre-industrial period is increased dust emission in the Southern Hemisphere and alterations in atmospheric transport. Wegner, A., Sudarchikova, N., Fischer, H., Mikolajewicz, U. (2014) Mineral Dust Variability in Antarctic Ice for Different Climate Change Conditions. Integrated Analysis of Interglacial Climate Dynamics (INTERDYNAMIC), 83-88.

Solar ultraviolet radiation and ozone depletion-driven climate change: effects on terrestrial ecosystems: The combination of climate change factors and UV-B has influenced terrestrial organisms and ecosystems in the Southern Hemisphere through ozone depletion. Findings include: UV-B radiation has a beneficial role in plant growth; the combination of UV-B radiation, UV-A radiation, and visible radiation are drivers of decomposition of decayed plant matter in grasslands and deserts; UV radiation can contribute to climate change through stimulation of plants’ volatile organic compounds, soils, and plant litter; the Southern Hemisphere’s depletion of ozone affects seasonal weather patterns. Bornman, J., Barnes, P., Robinson, S., Ballare, C., Caldwell, M. (2014) Solar ultraviolet radiation and ozone depletion-driven climate change: effects on terrestrial ecosystems. Photochemical & Photobiological Sciences, 14, 88-107.

Climate change enhances primary production in the western Antarctic Peninsula: There was a positive effect of intense regional warming in the western Antarctic Peninsula over the last 50 years on primary production. This study investigated ozone thickness, sea ice concentration, sea-surface temperature, incident irradiance, and chlorophyll a concentration in the western Antarctic Peninsula. The presence of the ozone hole and a sea ice retreat caused increased radiational exposure, and therefore an increased photoinhibition from September-November in the region, leading to the conclusion that there was a positive effect on primary production. Moreau, S., Mostajir, B., Bélanger, S., Schloss, I. R., Vancoppenolle, M., Demers, S. and Ferreyra, G. A. (2015), Climate change enhances primary production in the western Antarctic Peninsula. Global Change Biology. doi: 10.1111/gcb.12878.

Consistent evidence of increasing Antarctic accumulation with warming: Changes in surface mass balance in the Antarctic Ice Sheet support a negative contribution to sea level because of warmer air’s higher moisture capacity causing increased precipitation. Strong natural variability has made it difficult to find a correlation between observations of temperature and accumulation change. Both the ice-core data modeling results and the palaeo-simulations were used to create a projection of sea-level fall that competes with surface melting and other dynamical losses. Frieler, K., Clark, P., He, F., Buizert, C., Reese, R., Ligtenberg, S., Broeke, M., Winkelmann, R., Levermann, A. (2015). Consistent evidence of increasing Antarctic accumulation with warming. Nature Climate Change, 5, 348-352.

The Large-Scale Climate in Response to the Retreat of the West Antarctic Ice Sheet: Changes in the West Antarctic Ice Sheet (WAIS) lead to significant changes in the oceanic and atmospheric circulations. Modifications of the WAIS cause warmer conditions and a northward shift of the westerly flow. These alterations lead to alterations in deep water formation, thus enhancing the Antarctic Bottom water and lessening the size of North Atlantic Deep Water. Through evaluation of density flux, it was found that climate anomalies between Marine Isotope Stage 31 and current simulations resemble a bipolar seesaw pattern. F. Justino, A. S. Silva, M. P. Pereira, F. Stordal, D. Lindemann, and F. Kucharski, 2015: The large-scale climate in response to the retreat of the west antarctic ice sheet.J. Climate,28, 637–650.

Reconstruction of Westerly wind influence on West Antarctica shows current situation is unprecedented in past 100,000 years: A reconstruction of atmospheric circulation around Antarctica revealed that the recent southward migration of the westerly winds as expressed in the positive trend of the Southern Annular Mode (SAM) due to increases in greenhouse gases and ozone depletion has caused unprecedented marine air masses transport into West Antarctica which led to increased precipitation and a rise in temperature. Mayewski, P. A. et al. (2013) West Antarctica's sensitivity to natural and human-forced climate change over the Holocene. Journal of Quaternary Science 28, 40-48

Antarctic Climate Change and the Environment Turner, J., Bindschadler, R.A., Convey, P., Di Prisco, G., Fahrbach, E., Gutt, J., Hodgson, D.A., Mayewski, P.A., and Summerhayes, C.P.: 526 pp., 2009. Cambridge, SCAR. ISBN 978 0 948277 22 1

Positive trend of SAM not statistically significant in CMIP5: The intensification of the Westerly winds (or SAM) along the Amundsen / Bellinghausen Seas have been suggested as principle forcing for upwelling of warm, circum polar deep water, leading to rapid loss of ice from beneath ice shelves. A comparison of the CMIP5 modelling experiments for the IPCC representative concentration pathways RCP4.5 and RCP8.5 scenario projections distinguishes between model uncertainties and internal climate variability. The results indicate that due to large internal climate variability, the intensification of SAM is statistically significant in the CMIP5 model ensemble at one (two) sigma standard deviations only at 2030 (2065). Bracegirdle, T.J., Turner, J., Hosking, J.S., Phillips, T. (2014) Sources of uncertainty in projections of twenty-first century westerly wind changes over the Amundsen Sea, West Antarctica, in CMIP5 climate models, Climate Dynamics, 1-12.

Increase in Antarctic Sea Ice not captured in CMIP5 modelling experiments: A comparison of trends and annual variability of 18 models used in the CMIP5 ensemble runs shows unsurprisingly large inter-model variability. More importantly though, all models produce a negative sea ice trend, which is forced by an earlier trend. This suggests that the forcing mechanism causing the currently observed increase in the Ross Sea Region are not captured and simulated incorrectly. Turner, J., Bracegirdle, T., Phillips, T., Marshall, G., Hosking, J.S. (2013) An initial assessment of Antarctic Sea Ice Extent in the CMIP5 Models. Journal of Climate, 26, 1473-1484

Reconstruction of modern sea ice trends reveal longer term decline: An exceptionally high resolution reconstruction of seasonal sea ice variability over the past 130 years in the Ross Sea region suggests stable sea ice area until the mid 1950s, which is followed by a period characterised by significant sea ice reductions. However, since early 1990s a sea ice area increase of 5% is observed which masks the underlying declining trend. The strengthening of southerly wind flow across the Ross Sea polynya has been suggested as driving mechanism for the observed sea ice area increase. Sinclair, K., Bertler, N., Bowen, M., Arrigo, K. (2014) Twentieth century sea ice trends in the Ross Sea from a high resolution coastal ice core record. Geophysical Research Letters, 41:10, 3510-3515

Source of iron fertilisation in the Ross Sea region from ocean upwelling: Observations show that the Ross Sea polynya has low concentration of bio-available iron (Fe). Extensive algae blooms during summer indicate either an oceanic (upwelling) or atmospheric (dust from the Tran Antarctic Mountains) contribute significantly to the Fe budget in the Ross Sea and area of Antarctic Bottom Water formation. Analysis of Fe concentrations in sea ice and snow samples suggests that the Fe from atmospheric sources accounts for ~15% of the observed primary productions. This suggests that ocean upwelling is the major driver of Fe delivery and thus primary productivity. Thus changes in ocean currents (and to a lesser degree of atmospheric circulation) could influence the carbon uptake efficiency in the Ross Sea. Winton, V., Dunbar, G., Bertler, N., Millet, M.-A., Delmonte, B., Atkins, C., Chewings, J. and Andersson, P. (2014): The contribution of Aeolian sand and dust to iron fertilisation of phytoplankton blooms in the southwestern Ross Sea, Antarctica. Global Biogeochemical Cycles, 28: 4, 423-436

Scientific Committee on Antarctic Research
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