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The Tibetan Plateau (TP), the highest and largest plateau in the world, with complex and competing cryospheric‐hydrologic‐geodynamic processes, is particularly sensitive to anthropogenic warming. The quantitative water mass budget in the TP is poorly known. Here we examine annual changes in lake area, level, and volume during 1970s–2015. We find that a complex pattern of lake volume changes during 1970s–2015: a slight decrease of −2.78 Gt yr−1 during 1970s–1995, followed by a rapid increase of 12.53 Gt yr−1 during 1996–2010, and then a recent deceleration (1.46 Gt yr−1) during 2011–2015. We then estimated the recent water mass budget for the Inner TP, 2003–2009, including changes in terrestrial water storage, lake volume, glacier mass, snow water equivalent (SWE), soil moisture, and permafrost. The dominant components of water mass budget, namely, changes in lake volume (7.72 ± 0.63 Gt yr−1) and groundwater storage (5.01 ± 1.59 Gt yr−1), increased at similar rates. We find that increased net precipitation contributes the majority of water supply (74%) for the lake volume increase, followed by glacier mass loss (13%), and ground ice melt due to permafrost degradation (12%). Other term such as SWE (1%) makes a relatively small contribution. These results suggest that the hydrologic cycle in the TP has intensified remarkably during recent decades.

[1] The mass balance in the Inner Tibet Plateau (ITP) derived from the Gravity Recovery and Climate Experiment (GRACE) showed a positive rate that was attributed to the glacier mass gain, whereas glaciers in the region, from other field-based studies, showed an overall mass loss. In this study, we examine lake's water level and mass changes in the Tibetan Plateau (TP) and suggest that the increased mass measured by GRACE was predominately due to the increased water mass in lakes. For the 200 lakes in the TP with 4 to 7 years of ICESat data available, the mean lake level and total mass change rates were +0.14 m/yr and +4.95 Gt/yr, respectively. Compared those in the TP, 118 lakes in the ITP showed higher change rates (+0.20 m/yr and +4.28 Gt/yr), accounting for 59% area and 86% mass increase of the 200 lakes. The lake's mass increase rate in the ITP explains the 61% increased mass (~7 Gt/yr) derived from GRACE [Jacob et al., 2012], while it only accounts for 53% of the total lake area in the ITP.

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Temperature changes over the Tibetan Plateau (TP) exhibit a dependence on altitude, as observed from meteorological station data and Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) data. However, little is known about the changes in water surface temperature (WST) of lakes in the TP under the warming climate conditions over the past few decades. In this study, lake WST was examined using a MODIS/Terra 8 day LST (nighttime) product (MOD11A2) over the period 2001-2012. It was found that 52 lakes included in the analysis of WST exhibited an average rate of change of 0.012 ± 0.033°C/yr. Of these 52 lakes, 31 lakes (60%) displayed a temperature increase with a mean warming rate of 0.055 ± 0.033°C/yr and 21 lakes (40%) displayed a temperature decrease with a mean cooling rate of À0.053 ± 0.038°C/yr. The rates of change in WST for 13 lakes were statistically significant, and these included nine warming and four cooling lakes. Of the 17 lakes with nearby weather stations, nine lakes (53%) showed faster warming than nearby air/land. The warming lakes could be attributed to locally rising air and land surface temperatures as well as other factors such as the decreased lake ice cover. The cooling lakes were mostly located at high elevations (>4200 m), and the trend could have been due to increased cold water discharge to the lakes from accelerated glacier/snow melts. Therefore, both warming and cooling lake temperatures in the TP were possibly the result of increased air temperatures (0.036 ± 0.027°C/yr) under global warming conditions.

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Asia's high plateaus are sensitive to climate change and have been experiencing rapid warming over the past few decades. We found 99 new lakes and extensive lake expansion on the Tibetan Plateau during the last four decades, 1970–2013, due to increased precipitation and cryospheric contributions to its water balance. This contrasts with disappearing lakes and drastic shrinkage of lake areas on the adjacent Mongolian Plateau: 208 lakes disappeared, and 75% of the remaining lakes have shrunk. We detected a statistically significant coincidental timing of lake area changes in both plateaus, associated with the climate regime shift that occurred during 1997/1998. This distinct change in 1997/1998 is thought to be driven by large‐scale atmospheric circulation changes in response to climate warming. Our findings reveal that these two adjacent plateaus have been changing in opposite directions in response to climate change. These findings shed light on the complex role of the regional climate and water cycles and provide useful information for ecological and water resource planning in these fragile landscapes.