Changes in active layer thickness over the Qinghai‐Tibetan Plateau from 1995 to 2007

[1] The active layer over permafrost plays a significant role in surface energy balance, hydrologic cycle, carbon fluxes, ecosystem, and landscape processes and on the human infrastructure in cold regions. Over a period from 1995 to 2007, a systematic soil temperature measurement network of 10 sites was established along the Qinghai-Tibetan Highway. Soil temperatures up to 12 m depth were continuously measured semimonthly. In this study, we investigate spatial variations of active layer thickness (ALT) and its change over the period of record. We found that ALT can be estimated with confidence using semimonthly soil temperature profiles compared to those determined from available daily soil temperature profiles over the Qinghai-Tibetan Plateau. The primary results demonstrate that long-term and spatially averaged ALT is ∼2.41 m with a range of 1.32–4.57 m along the Qinghai-Tibetan Highway. All monitoring sites show an increase in ALT over the period of their records. The mean increasing rate of ALT is ∼7.5 cm/yr. ALT shows a closely positive correlation with the thawing index of air temperature on the plateau. We estimated ALT using the thawing index over a period from 1956 to 2005 near the Wudaoliang Meteorological Station in the northern plateau. ALT had no or very limited change from 1956 to 1983 and a sharp increase of ∼39 cm from 1983 to 2005. The magnitude of ALT increase is greater in the warm permafrost region than in the cold permafrost region. The primary control of increase in ALT is caused by an increase in summer air temperature, whereas changes in the winter air temperature and snow cover condition play no or a very limited role.

[1]  Liu Yongzhi,et al.  Ground temperature monitoring and its recent change in Qinghai–Tibet Plateau , 2004 .

[2]  Kenneth M. Hinkel,et al.  Spatial and temporal patterns of active layer thickness at Circumpolar Active Layer Monitoring (CALM) sites in northern Alaska, 1995–2000 , 2003 .

[3]  K. R. Everett,et al.  Glossary of Permafrost and Related Ground-Ice Terms , 1989 .

[4]  C. Tarnócai,et al.  Circumpolar‐Active‐Layer‐Monitoring (CALM) sites in the Mackenzie Valley, northwestern Canada , 2004 .

[5]  Knut Stamnes,et al.  Effects of Climate on the Active Layer and Permafrost on the North Slope of Alaska, U.S.A. , 1997 .

[6]  Qingbai Wu,et al.  Recent permafrost warming on the Qinghai‐Tibetan Plateau , 2008 .

[7]  R. Barry,et al.  Interdecadal changes in seasonal freeze and thaw depths in Russia , 2004 .

[8]  S. W. Muller,et al.  PERMAFROST OR PERMANENTLY FROZEN GROUND AND RELATED ENGINEERING PROBLEMS , 1948 .

[9]  H. Melling,et al.  Canadian cryospheric response to an anomalous warm summer: A synthesis of the climate change action fund project “the state of the arctic cryosphere during the extreme warm summer of 1998” , 2006 .

[10]  Sharon L. Smith,et al.  Active‐layer characteristics and summer climatic indices, Mackenzie Valley, Northwest Territories, Canada , 2009 .

[11]  L. Hinzman,et al.  Observations: Changes in Snow, Ice and Frozen Ground , 2007 .

[12]  Ketil Isaksen,et al.  Warming permafrost in European mountains , 2003 .

[13]  The PACE monitoring strategy: A concept for permafrost research in Qinghai–Tibet , 2006 .

[14]  Sharon L. Smith,et al.  Climate warming and active layer thaw in the boreal and tundra environments of the Mackenzie Valley1 , 2007 .

[15]  Daqing Yang,et al.  Changes of climate and seasonally frozen ground over the past 30 years in Qinghai–Xizang (Tibetan) Plateau, China , 2004 .

[16]  S. Yongping.  Permafrost Change and Its Effect on Eco-environment in the Source Regions of the Yangtze and Yellow Rivers , 2004 .

[17]  F. Nelson,et al.  The Circumpolar Active Layer Monitoring (CALM) Workshop and THE CALM II Program , 2004 .

[18]  T. Osterkamp.  The recent warming of permafrost in Alaska , 2005 .

[19]  Roger G. Barry,et al.  An Amplified Signal of Climatic Change in Soil Temperatures during the Last Century at Irkutsk, Russia , 2001 .

[20]  C. Burn.  The active layer: two contrasting definitions , 1998 .

[21]  K. Hinkel,et al.  Seasonal patterns of coupled flow in the active layer at three sites in northwest North America , 1997 .

[22]  Vladimir E. Romanovsky,et al.  Interannual variations of the thermal regime of the active layer and near‐surface permafrost in northern Alaska , 1995 .

[23]  C. E. Thorn,et al.  Statistical relationships between daily and monthly air and shallow‐ground temperatures in Kärkevagge, Swedish Lapland , 1999 .

[24]  Roger G. Barry,et al.  Spatial and temporal variability in active layer thickness over the Russian Arctic drainage basin , 2005 .

[25]  G. Cheng,et al.  Technical approaches on permafrost thermal stability for Qinghai–Tibet Railway , 2006 .

[26]  G. Cheng,et al.  Responses of permafrost to climate change and their environmental significance, Qinghai‐Tibet Plateau , 2007 .

[27]  Wang Qing-chun.  Response of Permafrost over Qinghai Plateau to Climate Warming , 2005 .

[28]  R. Barry,et al.  Statistics and characteristics of permafrost and ground-ice distribution in the Northern Hemisphere , 1999 .

[29]  F. Nelson,et al.  The circumpolar active layer monitoring (calm) program: Research designs and initial results , 2000 .

[30]  L. Thompson,et al.  Accumulation Rates over the Past 500 Years Recorded in Ice Cores from the Northern and Southern Tibetan Plateau, China , 2007 .

[31]  E. S. Melnikov,et al.  Circum-Arctic map of permafrost and ground-ice conditions , 1997 .

[32]  Tingjun Zhang.  Influence of the seasonal snow cover on the ground thermal regime: An overview , 2005 .