Prevailing climatic trends and runoff response from Hindukush-Karakoram-Himalaya, upper Indus basin

TL;DR

This study analyzes climate and runoff trends in the Hindukush-Karakoram-Himalaya region from 1961 to 2012, revealing significant seasonal temperature changes and their impact on regional hydrology and runoff regimes.

Contribution

It provides a comprehensive statistical assessment of spatial and temporal climatic trends and their relation to runoff in the Upper Indus Basin, addressing the Karakoram Anomaly.

Findings

Significant seasonal warming and cooling trends identified.

Spatially significant climatic trends largely agree with runoff changes.

Dominance of nival or glacial runoff regimes influenced by climate trends.

Abstract

We analyze trends in maximum, minimum and mean temperatures (Tx, Tn, and Tavg, respectively), diurnal temperature range (DTR) and precipitation from 18 stations (1250-4500 m asl) for their overlapping period of record (1995-2012), and separately, from six stations of their long term record (1961-2012). We apply Mann-Kendall test on serially independent time series to assess existence of a trend while true slope is estimated using Sen s slope method. Further, we statistically assess the spatial scale (field) significance of local climatic trends within ten identified sub-regions of UIB and analyze whether the spatially significant (field significant) climatic trends qualitatively agree with a trend in discharge out of corresponding sub-region. Over the recent period (1995-2012), we find a well agreed and mostly field significant cooling (warming) during monsoon season i.e. July-October (March-May and November), which is higher in magnitude relative to long term trends (1961-2012). We also find ... The observed hydroclimatic trends, being driven by certain changes in the monsoonal system and westerly disturbances, indicate dominance (suppression) of nival (glacial) runoff regime, altering substantially the overall hydrology of UIB in future. These findings largely contribute to address the hydroclimatic explanation of the Karakoram Anomaly.