Ice records provide a qualitative rather than a quantitative indication of the trend of climate change. Using the bulk aerodynamic method and degree day model, this study quantified ice mass loss attributable to sublimation/evaporation (S/E) and meltwater on the basis of integrated observations (1960-2006) of glacier-related and atmospheric variables in the northeastern Tibetan Plateau. During 1961-2005, the average annual mass loss in the ice core was 95.33 +/- 20.56 mm w.e. (minimum: 78.97 mm w.e. in 1967, maximum: 146.67 mm w.e. in 2001), while the average ratio of the revised annual ice accumulation was 21.2 +/- 7.7% (minimum: 11.0% in 1992, maximum 44.8% in 2000). A quantitative formula expressing the relationship between S/E and air temperature at the monthly scale was established, which could be extended to estimation of S/E changes of other glaciers in other regions. The elevation effect on alpine precipitation determined using revised ice accumulation and instrumental data was found remarkable. This work established a method for quantitative assessment of the temporal variation in ice core mass loss, and advanced the reconstruction of long-term precipitation at high elevations. Importantly, the formula established for reconstruction of S/E from temperature time series data could be used in other regions.

Biomass burning play a key role in the global carbon cycle by altering the atmospheric composition, and affect regional and global climate. Despite its importance, a very few high-resolution records are available worldwide, especially for recent climate change. This study analyzes levoglucosan, a specific tracer of biomass burning emissions, in a 38-year ice core retrieved from the Shulehe Glacier No. 4, northeastern Tibetan Plateau. The levoglucosan concentration in the Shulehe Glacier No. 4 ice core ranged from 0.1 to 55 ng mL(-1), with an average concentration of 8 +/- 8 ng mL(-1). The concentrations showed a decreasing trend from 2002 to 2018. Meanwhile, regional wildfire activities in Central Asian also exhibited a declining trend during the same period, suggesting the potential correspondence between levoglucosan concentration of the Shulehe Glacier No. 4 ice core and the fire activity of Central Asia. Furthermore, a positive correlation also exists between the levoglucosan concentration of the Shulehe Glacier No. 4 ice core and the wildfire counts in Central Asia from 2002 to 2018. While backward air mass trajectory analysis and fire spots data showed a higher distribution of fire counts in South Asia compared to Central Asia, but the dominance of westerly circulation in the northern TP throughout the year. Therefore, the levoglucosan in the Shulehe Glacier No. 4 provides clear evidence of Central Asian wildfire influence on Tibetan Plateau glaciers through westerlies. This highlights a great importance of ice core data for wildfire history reconstruction in the Tibetan Plateau Glacier regions.

Black Carbon (BC), as a driver of environmental change, could significantly impact the snow by accelerating melting and decreasing albedo. Systematic documentation of BC studies is crucial for a better understanding of its spatial and temporal trends. This study reviewed the BC studies in the ice core and remote lake sediments and their sources in the northern hemisphere. The literature surveyed points to around 2.9 to 3.7 times increase of BC in the European Alps and up to a three-fold increase of BC in the Himalayan-Tibetan Plateau (HTP) after the onset of industrialization in Europe and Asia, respectively. BC concentration from Greenland ice core showed seven times increase with an interrupted trend after 1950's. South Asian emissions were dominant in the HTP along with a contribution from the Middle East, whereas Western European and local emissions were responsible for the change in BC concentration in the European Alps. In the Arctic, contributions from North America, Europe and Asia persisted. Similarly, a historical reconstruction of lake sediments records demonstrates the effects of emissions from long-range transport, sediment focusing, local anthropogenic activities, precipitation and total input of flux on the BC concentration.

Refractory black carbon (rBC) is an important climate-forcing agent emitted by biomass burning and fossil fuel combustion. Antarctica can receive rBC aerosols emitted in Southern Hemisphere (SH) and preserve the history of emissions and atmospheric transport. Here, we present a high-resolution record of rBC in an ice core (CA2016-75) acquired from the coastal Eastern Antarctica, which accumulated during the past 100 years (1915-2015). The rBC concentration (0.030 ng g(-1)) and flux (7.22 mu g m(-2) yr(-1)) are both among the lowest values in Antarctic snow and ice. The rBC concentration reaches higher values on average in the period aligned with the austral Winter. The rBC concentrations show a long-term descending trend during the period between 1950s and mid-1990s, followed by an ascending trend to 2015. Back trajectory analysis indicates that the emissions resulting from the biomass burning and anthropogenic biofuel consumption in Southern America and Australia were the main sources for the rBC deposition. Wavelet spectral analysis and temporal correlation analysis on rBC deposition and the atmospheric circulation indices (El Nino-Southern Oscillation, Southern Annular Mode and Antarctic Oscillation) confirmed that the atmospheric circulations have certain influences on the rBC deposition, likely by their direct effects on rBC transport and on weather conditions driving the occurrence of fires and subsequent emissions in source regions.

While Arctic sea ice has been decreasing in recent decades that is largely due to anthropogenic forcing, the extent of Antarctic sea ice showed a positive trend during 1979-2015, followed by an abrupt decrease. The shortness of the satellite record limits our ability to quantify the possible contribution of anthropogenic forcing and internal variability to the observed Antarctic sea ice variability. In this study, ice core and fast ice records with annual resolution from six sites are used to reconstruct the annualresolved northernmost latitude of sea ice edge (NLSIE) for different sectors of the Southern Ocean, including the Weddell Sea (WS), Bellingshausen Sea (BS), Amundsen Sea (AS), Ross Sea (RS), and the Indian and western Pacific Ocean (IndWPac). The linear trends of the NLSIE are analyzed for each sector for the past 100-200 years and found to be -0.08 degrees, -0.17 degrees, +0.07 degrees, +0.02 degrees, and -0.03 degrees per decade (>95% confidence level) for the WS, BS, AS, RS, and IndWPac, respectively. For the entire Antarctic, our composite NLSIE shows a decreasing trend (-0.03 degrees per decade, 99% confidence level) during the 20th century, with a rapid decline in the mid-1950s. It was not until the early 1980s that the observed increasing trend occurred. A comparison with major climate indices shows that the long-term linear trends in all five sectors are largely dominated by the changes in the Southern Annular Mode (SAM). The multi-decadal variability in WS, BS, and AS is dominated by the Interdecadal Pacific Oscillation, whereas that in the IndWPac and RS is dominated by the SAM. (c) 2021 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.

Black carbon (BC) can be transported over long distances and is an important trigger of climate warming and glacier melting at remote high mountains and polar regions. It is normally assumed that the variation of BC flux in remote regions is dominated by its emissions. However, after a comprehensive investigation of potential influencing factors on temporal variations of BC from ice cores of the Himalayas, this short communication shows that in addition to BC emissions, contributions from dust storms and precipitation are also important (up to 56% together) in regulating the variation of BC deposition flux and concentrations derived from remote Himalayan ice core measurements. Therefore, besides BC emissions, the influence of precipitation and BC transported by dust storms should also be considered to better quantify the lifetime and behavior of BC during its long-range transport from source to sink regions as well as to quantify the climatic effects of BC over remote Himalayan glaciers.

In this study, a shallow ice core (12.5 m, called LGB) was drilled at the Lambert Glacial Basin, East Antarctica. The major ion and metal elements were measured at 5-6 cm resolution in this shallow core, which covered the period 1990-2017. Therefore, an annual-resolution record of iron (Fe) concentrations and fluxes were reconstructed in this shallow ice core. Although the Fe data is comparable to previous results, our results emphasized that much more dissolved Fe (DFe) from the Cerro Hudson volcanic event (August 1991) was transported to the East Antarctic ice sheet, in comparison with the Pinatubo volcanic event (June 1991). The aeolian dust may be the primary DFe source during 1990-2017. In particular, the DFe variations may be affected by the biomass burning emissions in two periods (1990-1998 and 2014-2017). While total dissolved Fe (TDFe) variations were controlled by the climatic conditions since 2000 because of the temperature (delta O-18) decreasing at East Antarctica. These Fe data will be useful to assess the modern bioavailable Fe release for the Antarctica ice sheet. (C) 2020 Elsevier Ltd. All rights reserved.

This study reports on the measurements of ion and refractory black carbon (rBC) concentrations in a shallow (10.96 m) ice core sample which was drilled from the field site of the East Greenland Ice Core Project (EGRIP) in July, 2016. The results provide a recent record of rBC deposition in the East Greenland ice sheet from 1990 to 2016. The annual variability in oxygen (delta O-18) and hydrogen (delta D) isotopic compositions indicated that notably warm events occurred since 2008. Peaks in rBC occurred during summer seasons, which may be attributed to the burning of biomass in boreal summer. The rBC record and analysis of historical air trajectories using the HYSPLIT model indicated that anthropogenic BC emissions from Russia, North America and Europe contributed to the majority of rBC deposition in the Greenland region, and a reduction in anthropogenic BC consumption in these areas played a dominant role in the decrease in BC concentrations since 2000. This record also suggests that the emissions from the East Asian region (China) contributed very little to the recorded BC concentrations in East Greenland ice core. The model results indicated that radiative forcing due to BC had decreased significantly since 1990, and had remained below 0.02W m(-2) since 2000.

Atmospheric nitrogen deposition is an important contributor to global and regional nitrogen cycles, and atmospheric nitrogen could be a critical limit nutrient for remote areas. In this study, nitrogen species compositions, deposition fluxes, and historical records in the mountains of Western China, including the Tibetan Plateau, were determined from snowpit and ice core samples collected from mountain glaciers. The mean concentration of total dissolved nitrogen (TDN) in the snowpit samples was 12.6 mu mol L-1 (8.0-17.8 mu mol L-1) and comprised 59% ammonium nitrogen, 35% nitrate nitrogen, and similar to 6% dissolved organic nitrogen. The deposition of nitrogen species, except organic nitrogen (likely due to its low concentrations and/or different origination), varied seasonally in a similar way based on the records of the snowpit profile. Based on monthly surface sample collection in one of the glaciers, the mass concentration and composition of nitrogen species varied monthly, mainly because of melting processes. During melting, the inorganic nitrogen content could be lost significantly, whereas the dissolved organic nitrogen concentration could be enriched because of microbial activity. For the historical records, the nitrogen deposition in mountain areas of Western China after 1960s was increased by about one time of that during 1900-1950 and was dominated by ammonium-N. From the snowpit data, we estimated the total dissolved nitrogen deposition flux at 0.56-1.3 (mean 0.88) kg ha(-1) a(-1) in the mountain area of Western China. These results could improve our understanding of nitrogen deposition and cycle in the mountain areas of Western China.

This study reports on the measurements of ion and refractory black carbon (rBC) concentrations in a shallow (10.96 m) ice core sample which was drilled from the field site of the East Greenland Ice Core Project (EGRIP) in July, 2016. The results provide a recent record of rBC deposition in the East Greenland ice sheet from 1990 to 2016. The annual variability in oxygen (delta O-18) and hydrogen (delta D) isotopic compositions indicated that notably warm events occurred since 2008. Peaks in rBC occurred during summer seasons, which may be attributed to the burning of biomass in boreal summer. The rBC record and analysis of historical air trajectories using the HYSPLIT model indicated that anthropogenic BC emissions from Russia, North America and Europe contributed to the majority of rBC deposition in the Greenland region, and a reduction in anthropogenic BC consumption in these areas played a dominant role in the decrease in BC concentrations since 2000. This record also suggests that the emissions from the East Asian region (China) contributed very little to the recorded BC concentrations in East Greenland ice core. The model results indicated that radiative forcing due to BC had decreased significantly since 1990, and had remained below 0.02W m(-2) since 2000.