3.4 Relationship between lake level changes and precipitation
variations
Since
the late 1990s, the expansion of Tibetan lakes has been mainly affected
by regional climate changes such as increased water vapor content,
potential evaporation reduction and significantly enhanced air
convection. (Yang et al. 2014; Yang et al. 2011; Lei et al. 2017; Lu et
al. 2015). Therefore, with the acceleration of climate warming and
humidification, precipitation could be also gradually increase (Yang et
al. 2014), which supports the observation of the rapid lake expansion in
the TP.
As shown in Fig. 3 and supplementary materials (Fig. S1), the trends of
lake level changes since 1990 are generally consistent with previous
studies. Our findings reveal that the drastic water level jumps in
Tibetan lakes since 2016, has been a result of continued precipitation
increase after a relatively drier period from 2012 to 2016. This
suggests that precipitation remains to be a first-order driver of
Tibetan lake dynamics. It was found that the drastic increase of lake
level in 2017-2018 was consistent with the increase of precipitation in
the near past several years, so the monthly precipitation data in recent
years was selected and compared with the lake level. According to the
study, the monthly precipitation and the lake water level during the
period 2013-2018 were selected to study the influence of specific
monthly precipitation on the lake water level. The most prominent
feature was the good correspondence between lake level increase and the
summer precipitation. In addition, we can find that the decrease of
water level in individual years (e.g. 2015) corresponded to less summer
precipitation. The amplitude of wet season lake level increases showed a
good relationship with precipitation amount. For example, the drastic
lake level rises in 2017 and 2018 in the TP corresponded to high
precipitation. This suggests that the excessive precipitation during the
wet season of 2017 and 2018 played a crucial role in the recent lake
level increase. Overall, precipitation appears to play a more dominant
role than temperature (and its induced glacier/permafrost melting). This
was implied by the fact warming-induced melting did not reverse the
slow-down or hiatus of lake expansion before 2016 (when precipitation
was less), and it would have to be the precipitation increase again that
eventually triggered another round of lake level increase. More details
on other lakes and meteorological stations can be found in the
Supplement (Fig. S2).