A high-resolution 2ooo-year methane record has been constructed from an ice core recovered at 7200 m a.s.1, on the Dasuopu Glacier in the central Himalayas. This sub-tropical methane record reveals an increasing trend...A high-resolution 2ooo-year methane record has been constructed from an ice core recovered at 7200 m a.s.1, on the Dasuopu Glacier in the central Himalayas. This sub-tropical methane record reveals an increasing trend in the concentration of methane during the industrial era that is similar to observations from polar regions. However, we also observed the differences in the atmospheric methane mixing ratio between this monsoon record and those from polar regions during pre-industrial times. In the time interval o N 1850 A.D., the average methane concentration in the Dasuopu ice core was 782±40 ppbv and the maximum temporal variation exceeded 200 ppbv. The difference gradient of methane concentration in Dasuopu ice core with Greenland and Antarctica cores are 66±40 ppbv and 107±40 ppbv, respectively. This suggests that the tropical latitudes might have acted as a major global methane source in preindustrial times. In addition, the temporal fluctuation of the pre-industrial methane records suggests that monsoon evolution incorporated with high methane emission from south Asia might be responsible for the relatively high methane concentration observed in the Dasuopu ice core around A.D. 800 and A.D. 1600. These results provide a rough understanding of the contribution of tropical methane source to the global methane budget and also the relationship betweenatmospheric methane and climate change.展开更多
During migration, birds can show different responses to wind in relation to distance to the goal, experience, ecologi- cal barriers and visibility of landmarks. We analysed the effect of wind （tailwinds and crosswind...During migration, birds can show different responses to wind in relation to distance to the goal, experience, ecologi- cal barriers and visibility of landmarks. We analysed the effect of wind （tailwinds and crosswinds） on daily movement rates （for- ward and perpendicular） of Eleonora＇s falcons using ARGOS satellite telemetry, during their trans-continental autumn migration to Madagascar, in relation to the different crossed regions and individuals＇ age class. Our results showed that the effect of wind on daily movement rates was not uniform, being stronger in the farthest region from the migration goal, the Sahara desert, with adults being more affected than juveniles in this region. In the Sahel, the results were more conflicting, perhaps because daily movements were more shaped by the distribution of food resources. In Equatorial Africa, daily movement rates were mainly af- fected by crosswinds. Still, it remains unclear which orientation mechanism allows Eleonora＇s falcons to reach such a narrow wintering area compensating also for wind displacement展开更多
基金supported by the National Natural Science Foundation of China (40671044)the Ministry of Science and Technology of China (2005CB422004)
文摘A high-resolution 2ooo-year methane record has been constructed from an ice core recovered at 7200 m a.s.1, on the Dasuopu Glacier in the central Himalayas. This sub-tropical methane record reveals an increasing trend in the concentration of methane during the industrial era that is similar to observations from polar regions. However, we also observed the differences in the atmospheric methane mixing ratio between this monsoon record and those from polar regions during pre-industrial times. In the time interval o N 1850 A.D., the average methane concentration in the Dasuopu ice core was 782±40 ppbv and the maximum temporal variation exceeded 200 ppbv. The difference gradient of methane concentration in Dasuopu ice core with Greenland and Antarctica cores are 66±40 ppbv and 107±40 ppbv, respectively. This suggests that the tropical latitudes might have acted as a major global methane source in preindustrial times. In addition, the temporal fluctuation of the pre-industrial methane records suggests that monsoon evolution incorporated with high methane emission from south Asia might be responsible for the relatively high methane concentration observed in the Dasuopu ice core around A.D. 800 and A.D. 1600. These results provide a rough understanding of the contribution of tropical methane source to the global methane budget and also the relationship betweenatmospheric methane and climate change.
文摘During migration, birds can show different responses to wind in relation to distance to the goal, experience, ecologi- cal barriers and visibility of landmarks. We analysed the effect of wind （tailwinds and crosswinds） on daily movement rates （for- ward and perpendicular） of Eleonora＇s falcons using ARGOS satellite telemetry, during their trans-continental autumn migration to Madagascar, in relation to the different crossed regions and individuals＇ age class. Our results showed that the effect of wind on daily movement rates was not uniform, being stronger in the farthest region from the migration goal, the Sahara desert, with adults being more affected than juveniles in this region. In the Sahel, the results were more conflicting, perhaps because daily movements were more shaped by the distribution of food resources. In Equatorial Africa, daily movement rates were mainly af- fected by crosswinds. Still, it remains unclear which orientation mechanism allows Eleonora＇s falcons to reach such a narrow wintering area compensating also for wind displacement
