Description: Fractional abunances of isoprenoid GDGTs calculated from the peak areas detected for the molecule peaks in the HPLC chromatograms. These data are an addition to the already archived TEX86 and UK'37 data in core-top sediments from off Indonesia (doi:10.1594/PANGAEA.823057).

Description: In this study we reconstruct sea surface temperatures (SSTs) using two lipid-based biomarker proxies (alkenone unsaturation index UK'37 and TEX86 index based on glycerol dibiphytanyl glycerol tetraethers) in 36 surface sediment samples from the Indonesian continental margin off west Sumatra and south of Java and the Lesser Sunda Islands. Comparison of measured temperatures (World Ocean Atlas 09) to reconstructed temperatures suggests that SST-UK'37 reflects the SE monsoon SST in the upwelling area south of Java and the Lesser Sunda Islands, whereas Temp-TEXH86 estimates are up to 2°C lower than SST-UK'37. This offset is possibly related to either one or a combination of two factors: i) the depth habitats of the source organisms; ii) different seasonal production and/ or seasonality of export associated with phytoplankton blooming triggered by primary productivity. In the non-upwelling area off west Sumatra, the alkenone-based SSTs are cooler than measured temperatures during the entire year, likely due to the reduced sensitivity of the UK'37 proxy beyond 28°C. However, reconstructed temperatures based on TEXH86 are consistent with mean annual SST, implying that the Temp-TEXH86 reflects the mean annual SST in the non-upwelling area of the tropical Eastern Indian Ocean.

Description: In this study, we obtained concentrations and abundance ratios of long-chain alkenones and glycerol dialkyl glycerol tetraethers (GDGTs) in a one-year time-series of sinking particles collected with a sediment trap moored from December 2001 to November 2002 at 2200 m water depth south of Java in the eastern Indian Ocean. We investigate the seasonality of alkenone and GDGT fluxes as well as the potential habitat depth of the Thaumarchaeota producing the GDGTs entrained in sinking particles. The alkenone flux shows a pronounced seasonality and ranges from 1 µg m-**2 d**-1 to 35 µg m**-2 d**-1. The highest alkenone flux is observed in late September during the Southeast monsoon, coincident with high total organic carbon fluxes as well as high net primary productivity. Flux-weighted mean temperature for the high flux period using the alkenone-based sea-surface temperature (SST) index UK'37 is 26.7°C, which is similar to satellite-derived Southeast (SE) monsoon SST (26.4°C). The GDGT flux displays a weaker seasonality than that of the alkenones. It is elevated during the SE monsoon period compared to the Northwest (NW) monsoon and intermonsoon periods (approximately 2.5 times), which is probably related to seasonal variation of the abundance of Thaumarchaeota, or to enhanced export of GDGTs by aggregation with sinking phytoplankton detritus. Flux-weighted mean temperature inferred from the GDGT-based TEXH86 index is 26.2°C, which is 1.8 °C lower than mean annual (ma) SST but similar to SE monsoon SST. As the time series of TEXH86 temperature estimates, however, does not record a strong seasonal amplitude, we infer that TEXH86 reflects ma upper thermocline temperature at approximately 50 m water depth.

Description: In this study, we obtained concentrations and abundance ratios of long-chain alkenones and glycerol dialkyl glycerol tetraethers (GDGTs) in a one-year time-series of sinking particles collected with a sediment trap moored from December 2001 to November 2002 at 2200 m water depth south of Java in the eastern Indian Ocean. We investigate the seasonality of alkenone and GDGT fluxes as well as the potential habitat depth of the Thaumarchaeota producing the GDGTs entrained in sinking particles. The alkenone flux shows a pronounced seasonality and ranges from 1 µg m-2 d-1 to 35 µg m-2 d-1. The highest alkenone flux is observed in late September during the Southeast monsoon, coincident with high total organic carbon fluxes as well as high net primary productivity. Flux-weighted mean temperature for the high flux period using the alkenone-based sea-surface temperature (SST) index UK’37 is 26.7°C, which is similar to satellite-derived Southeast (SE) monsoon SST (26.4°C). The GDGT flux displays a weaker seasonality than that of the alkenones. It is elevated during the SE monsoon period compared to the Northwest (NW) monsoon and intermonsoon periods (approximately 2.5 times), which is probably related to seasonal variation of the abundance of Thaumarchaeota, or to enhanced export of GDGTs by aggregation with sinking phytoplankton detritus. Flux-weighted mean temperature inferred from the GDGT-based TEXH86 index is 26.2°C, which is 1.8 °C lower than mean annual (ma) SST but similar to SE monsoon SST. As the time series of TEXH86 temperature estimates, however, does not record a strong seasonal amplitude, we infer that TEXH86 reflects ma upper thermocline temperature at approximately 50 m water depth.

Description: Sea surface temperature (SST) is very important for studies of the Earth’s climate system owing to the linkages between SST and various climatic processes. A reliable estimation of past SSTs is one of the main goals for paleoclimatologists to improve our understanding of oceanic and atmospheric dynamics and their connection to the global climate. Furthermore, the tropical SSTs play a key role for rapid climatic changes, because large amounts of heat and water vapor were transported from the tropics to the high latitudes. Warm SSTs at low latitude result in more evaporation and could thus induce increased ice sheet size and decreased temperatures at northern high latitudes. Establishing SST evolution in the tropics is crucial for understanding the mechanisms behind abrupt climate changes in the past. In this thesis, the main objectives are to evaluate the applicability of the UK’37 (alkenone unsaturation index) and TEXH86 (tretraether index of glycerol dialkyl glycerol tetraether with 86 carbon atoms) in the tropical Indian Ocean as well as to investigate their control mechanisms for reconstructing temperatures in the past. All studies presented herein are based on 36 surface sediments, a sediment trap covering an annual cycle and a gravity core in the eastern Indian Ocean. To assess the applicability, surface sediment samples from the Indonesian continental margin off west Sumatra, south of Java, and off the Lesser Sunda Islands are measured. In the non-upwelling regions, the results show that the UK’37 temperature estimates are up to 2 °C lower than World Ocean Atlas 2009 (WOA09) during the entire year, likely due to the reduced sensitivity of the UK’37 proxy beyond 28 °C. However, the temperatures based on TEXH 86 are consistent with mean annual temperatures from the WOA09. In the upwelling areas, the UK’37-based temperature estimates reflect the SST during the upwelling season, whereas the TEXH86-based temperature estimates are up to 2 °C lower than UK’37-based temperature estimates suggesting GDGT export from greater and colder water depths around 40-50 m. In the following work, an annual time series sediment trap study was conducted in the central upwelling region off south of Java. A pronounced seasonality of alkenone flux is observed, whereas GDGT flux displayed a weaker seasonality in comparison. The calculated flux-weighted average UK’37-based temperature estimate is similar to the SE monsoon SST rather than mean annual SST. The average is based on those samples only that permitted a reliable SST estimate, i.e., mainly the samples from the SE monsoon period. On the other hand, the flux-weighted average temperature based on the TEXH86 is consistent with mean annual temperature at 50 m depth, indicating TEXH86-temperatures reflect the mean annual subsurface temperature instead of the surface temperature. These observations support the findings concluded in the surface sediment samples study. Based on results from sediment trap and surface sediment samples, the application of the two SST indices on samples from a gravity core is in order to investigate the climatic evolution covering the past 22,000 years off south of Java. In this study, the temperature reconstruction suggest a 3-4 °C cooling during the last glacial maximum (LGM) compared to modern conditions. The results also show that the TEXH86 temperature estimates are up to 2 °C warmer than SST-UK’37 during the last 22ka except during the LGM and during the late Holocene. The differences between the two SST indices are paralleled by G. bulloides percentages as a proxy for upwelling intensity, implying that the offset between two temperature proxies could be considered as the potential for reconstructing the upwelling intensity in the study area. In addition, the initial timing for the deglacial warming of GDGT temperature estimates started at ~18 ka, whereas the lowest UK’37 temperature estimates appeared in the middle of the Younger Dryas period (YD, ca. 12 ka) and the late Heinrich Stadial 1 period (HS1, ca. 15 ka). Our records reveal that the seasonal SSTs and mean annual subsurface temperatures were closely linked to climate changes occurring in both hemispheres, respectively. Thus, the combination of UK’37 and TEXH86 records and their difference give the complementary feedbacks on sea-water temperature developments in the past evolution in the tropical eastern Indian Ocean.

Description: In this study we reconstruct sea surface temperatures (SSTs) using two lipid-based biomarker proxies (alkenone unsaturation index View the MathML sourceU37K′ and TEX86 index based on glycerol dibiphytanyl glycerol tetraethers) in 36 surface sediment samples from the Indonesian continental margin off west Sumatra and south of Java and the Lesser Sunda Islands. Comparison of measured temperatures (World Ocean Atlas 09) to reconstructed temperatures suggests that SST estimates based on View the MathML sourceU37K′ reflect the SE monsoon SST in the upwelling area south of Java and the Lesser Sunda Islands. Estimates based on TEX86 using the calibration for temperatures 〉20 °C (View the MathML sourceTEX86H) are up to 2 °C lower than View the MathML sourceU37K′-based SSTs. This offset is possibly related to either one or a combination of two factors: (i) the depth habitats of the source organisms and (ii) different seasonal production and/or seasonality of export associated with phytoplankton blooming triggered by primary productivity. In the non-upwelling area off west Sumatra, the alkenone-based SSTs are cooler than measured temperatures during the entire year, likely reflecting the limitations of the View the MathML sourceU37K′ proxy beyond 28 °C, while reconstructed temperatures based on View the MathML sourceTEX86H are consistent with mean annual SST.

Description: Sustainability, Vol. 10, Pages 3228: Relevance Analysis on the Variety Characteristics of PM2.5 Concentrations in Beijing, China Sustainability doi: 10.3390/su10093228 Authors: Binxu Zhai Jianguo Chen Wenwen Yin Zhongliang Huang Air pollution has become one of the most serious environmental problems in the world. Considering Beijing and six surrounding cities as main research areas, this study takes the daily average pollutant concentrations and meteorological factors from 2 December 2013 to 13 October 2017 into account and studies the spatial and temporal distribution characteristics and the relevant relationship of particulate matter smaller than 2.5 μm (PM2.5) concentrations in Beijing. Based on correlation analysis and geo-statistics techniques, the inter-annual, seasonal, and diurnal variation trends and temporal spatial distribution characteristics of PM2.5 concentration in Beijing are studied. The study results demonstrate that the pollutant concentrations in Beijing exhibit obvious seasonal and cyclical fluctuation patterns. Air pollution is more serious in winter and spring and slightly better in summer and autumn, with the spatial distribution of pollutants fluctuating dramatically in different seasons. The pollution in southern Beijing areas is more serious and the air quality in northern areas is better in general. The diurnal variation of air quality shows a typical seasonal difference and the daily variation of PM2.5 concentrations present a “W” type of mode with twin peaks. Besides emission and accumulation of local pollutants, air quality is easily affected by the transport effect from the southwest. The PM2.5 and PM10 concentrations measured from the city of Langfang are taken as the most important factors of surrounding pollution factors to PM2.5 in Beijing. The concentrations of PM10 and carbon monoxide (CO) concentrations in Beijing are the most significant local influencing factors to PM2.5 in Beijing. Extreme wind speeds and maximal wind speeds are considered to be the most significant meteorological factors affecting the transport of pollutants across the region. When the wind direction is weak southwest wind, the probability of air pollution is greater and when the wind direction is north, the air quality is generally better.