Accumulation and geochemical evidence for the Little Ice Age episode in eastern Antarctica

Data on accumulation and concentration of chemical compounds recorded in an essentially unexplored area(Dome Argus)of the Indian Ocean sector of eastern Antarctica during the past 2,680 years(680 B.C. to 1999 A.D.) are presented. During the first 1, 700 years(680 B. C. to 1000 A. D.), the accumulation data shows a slightly decreasing trend, while chemical ions appear to be stable, representing a stable climatic condition. An intensive increasing trend of the accumulation occurred during the 12^(th) to 14^(th) century. The period from 15^(th) to 19^(th) century was characterized by a rapid reducing accumulation and concentrations of volatile compounds suffering post-depositional loss linked to sparse precipitation amount,which was temporally consistent with the Little Ice Age(LIA) episode. Comparison between observed accumulation rates with other eastern Antarctic ice cores show a consistent decreasing trend during LIA, while sea salt and dust-originated ions increased due to sea ice extent and intensified atmospheric transportation. Distribution of volcanic originated sulfate over the Antarctic continent show a significant change during the 15^(th) century, coincident with the onset of the LIA. These results are important for the assessment of Antarctic continent mass balance and associated interpretation of the Dome A deep ice core records.

A 2680-year record of sea ice extent in the Ross Sea and the associated atmospheric circulation derived from the DT401 East Antarctic ice core

Long time series of Antarctic sea ice extent （SIE） are important for climate research and model forecasting. A historic ice extent in the Ross Sea in early austral winter was rebuilt through sea salt ions in the DT401 ice core in interior East Antarctica. El Nino-Southern Oscillation （ENSO） had a significant influence on the sea salt deposition in DT401 through its influence on the Ross Sea SIE and the transport of sea salt inland. Spectral analysis also supported the influence of ENSO with a significant 2-6 a periodicity band. In addition, statistically significant decadal （10 a） and pentadecadal （50-70 a） periodicities suggested the existence of a teleconnection from the Pacific decadal oscillation （PDO）, which originated from sea surface temperature anomalies in the tropical Pacific Ocean. The first eigenvector of the empirical orthogonal function analysis （EOF1） showed lower values during the Medieval Warm Period （MWP）, while higher values were found in the Little Ice Age （LIA）. A higher frequency of ENSO events were found in the cold climatic stage, The post 1800 AD period was occupied by significant fluctuations of the EOF1, and PDO may be one of the influencing factors. The EOF1 values showed moderate fluctuations from 680 BC to 1000 AD, showing that the climate was relatively stable in this period.

Spatial distribution of marine chemicals along a transect from Zhongshan Station to the Grove Mountain area, Eastern Antarctica

This study investigates the regional distribution of marine aerosol originated species （Na＋, CI-, nss-SO42- and MSA） in the snow pits （or firn cores） collected along a transect between Zhongshan Station and the Grove Mountain area （450 km inland） on the eastern side of the Lambert Glacier Basin. Concentrations of Na＋ and Cl- decrease exponentially with distance from the coast to 100 km inland （i.e., 1500 m a.s.1.）. Statistical results demonstrate that distance from the coast inland and elevation af-fect the concentration of sea-salt originated ions in inland areas significantly. Increase of Cl-/Na＋ ratio and higher variability in its standard deviation suggest that there are other sources of ions in addition to sea-salt in inland areas of the Antarctic conti- nent. The concentrations of Na＋ and Cl- from nine sampling sites in the Grove Mountain area are relatively higher than those from sites along CHINARE transect, although all sites are at similar distance inland. This phenomenon indicates that the barri- er effect of the mountain may be the most important factor influencing ion deposition. In addition, nss-SO42- and MSA vary differently, with nss-SO42- decreasing with distance more significantly. This implies that sources and transporting pathways influence the deposition of the two sulfur compounds considerably, being supported by the spatial pattern of correlation coeffi- cients between the nss-SO42- and MSA.

Spatial and temporal variability of marine-origin matter along a transect from Zhongshan Station to Dome A,Eastern Antarctica

The spatiotemporal distribution pattern of marine-origin matter on the Antarctica ice sheet was used to study variations in the source regions, transport mechanisms and postdepositional influences. We present data on sea salt ions, sulfur components and stable isotopes from surface and snow pit samples collected along the transect route from Zhongshan Station to Dome A during the austral summer in 2012–2013. A general decreasing trend in the accumulation, sea salt ions and sulfur components occurred with increasing distance from the coast and increasing elevation. However, different sources of the marine components, transport pathways and post-depositional influences were responsible for their different spatial distribution patterns. The marine ions in the coastal snow pit varied seasonally, with higher sea salt ion concentrations in the winter and lower concentrations in the summer; the opposite pattern was found for the sulfur compounds. The sea ice area surrounding Antarctica was the main source region for the deposited sea salt and the open sea water for the sulfur compounds. No significant trends in the marine-origin components were detected during the past 3 decades. Several periods of elevated deposition of sea salt ions were associated with lower temperatures（based on δD and δ18O） or intensified wind fields. In comparison to the sea salt ions, the sulfur concentrations exhibited the opposite distribution patterns and were associated with changes in the surrounding sea ice extent.

Reflections on coastal inundation,climate change impact,and adaptation in built environment:progresses and constraints

Coastal inundation causes considerable impacts on communities and economies.Sea level rise due to climate change increases the occurrence of coastal flood events,creating more challenges to coastal societies.Here we intend to draw the understanding of coastal inundation from our early studies,and provide a silhouette of our approaches in assessing climate change impacts as well as developing risk-based climate adaptation.As a result,we impart a distinctive view of the adaption towards the integration of asset design,coastal planning and policy development,which reflect multiscale approaches crossing individual systems to regions and then nation.Having the approaches,we also discussed the constraints that would be faced in adaptation implementation.In this regard,we initially follow the risk approach by illustrating hazards,exposure and vulnerability in relation to coastal inundation,and manifest the impact and risk assessment by considering an urban environment pertinent to built,natural,and socioeconomic systems.We then extend the scope and recommend the general approaches in developing adaptation to coastal inundation under climate change towards ameliorating overall risks,practically,by the reduction in exposure and vulnerability in virtue of the integration of design,planning and polices.In more details,a resilience design is introduced,to effectively enhance the capacity of built assets to resist coastal inundation impact.We then emphasize on the cost-effective adaptation for coastal planning,which delineates the problem of under-adaptation that leaves some potential benefits unrealized or over-adaptation that potentially consumes an excessive amount of resources.Finally,we specifically explore the issues in planning and policies in mitigating climate change risks,and put forward some emerging constraints in adaptation implementation.It suggests further requirements of harmonizing while transforming national policies into the contents aligned with provincial and local governments,communities,and households.

Dating a 109.9 m ice core from Dome A (East Antarctica) with volcanic records and a firn densification model

A 109.9 m ice core was extracted at a location about 300 m away from the Dome A summit （80°00′S, 77°21″E） by the Chinese team of the International Trans-Antarctic Science Expedition （ITASE） during the 21st Chinese National Antarctica Research Expedition （CHINARE） in January 2005. Two independent methods were used for dating the ice core, volcanic event markers shown by prominent non-sea-salt sulfate （nss-SO4^2-） and the Herron and Langway （H-L） firn densification model. Six promi- nent volcanic events （Agung 1963 AD, Tambora 1815 AD, Kuwae 1453 AD, Unknown 1259 AD, Taupo 186 AD and Pinatubo 1050 BC） were identified by comparison with other Antarctic ice cores. Based on the mean accumulation rates be- tween adjacent events, we estimate the age at the tim pore close-off depth （102 m） was 3516±100 a BP. This is the oldest close-off age ever reported from the Antarctic and the Greenland ice sheets. Calculations using the H-L model show that the age at the same depth is 3581±100 a BP. The two dating techniques differ by 65 years, or -1.8% of the record. We calculated the bottom age of the ice core as 4009±150 a BP using the volcanic dating method and 4115±150 a BP using the H-L model method.