The contribution of Middle East irrigation to the growth of the Karakoram glacier

Abstract Globally, ice sheets and mountain glaciers are on the decline [1-5]. However, satellite and ground data have shown an anomalous glacier gain over the Karakoram (KK) glacier in the northwestern Qinghai-Tibet Plateau[3, 6-12]. Presently, scientific consensus has not yet been established on the causal mechanisms responsible for this glacier gain. Here, we hypothesize that this KK mass gain is possibly attributed to irrigation in the Middle East (ME) through atmospheric teleconnection (KK-ME hypothesis). First, using observations from the Gravity Recovery and Climate Experiment (GRACE) and Global Precipitation Climatology Project (GPCP), we show mass and precipitation loss in the ME but both gain in the KK. Then, we test the KK-ME hypothesis using simulated differences in precipitation resulting from the irrigation and non-irrigation cases in the Community Atmosphere Model and Community Land Model. The result suggests that ME irrigation increases the amount of evaporated moisture. The excess water vapour is transferred to the KK by the strengthened westerly water vapour transport, increasing the simulated precipitation by approximately 30% around the KK region.