Air Temperature Regulates Erodible Landscape, Water, and Sediment Fluxes in the Permafrost‐Dominated Catchment on the Tibetan Plateau

Abstract

Approximately 40% of the Tibetan Plateau (TP) is underlain by continuous permafrost, yet its impact on fluvial water and sediment dynamics remains poorly investigated. Here we show that water and sediment dynamics in the permafrost‐dominated Tuotuohe basin on the TP are driven by air temperature and permafrost thaw, based on 33‐year daily in situ observations (1985–2017). Air temperature regulates the seasonal patterns of discharge and suspended sediment concentration (SSC) by controlling the changes in active contributing drainage area (ACDA, the unfrozen erodible landscape that contributes hydrogeomorphic processes within a catchment) and governing multiple thermal processes such as glacier‐snow melt and permafrost thaw. Rainstorms determine the short‐lived fluvial extreme events by intensifying slope processes and channel erosion and likely also by enhancing thaw slumps. Furthermore, the SSCs at equal levels of discharges are lower in autumn (September–October) than in spring (May–June) and summer (July–August). This reduced sediment availability in autumn can possibly be attributed to the increased supra‐permafrost groundwater runoff and the reduced surface runoff and erosion. Due to rapid climate warming, the ACDA has increased significantly from 1985 to 2017, implying expanding erodible landscapes for hydrogeomorphic processes. As a result, the fluvial water and sediment fluxes have substantially increased. In a warmer and wetter future for the TP, the fluvial sediment fluxes of similar permafrost‐underlain basins will continue to increase with expanding erodible landscapes and intensifying thermal and pluvial‐driven geomorphic processes. Thus, permafrost thaw should be considered as an important driver of past and future water and sediment changes for the TP.

Constraining Dynamic Sediment‐Discharge Relationships in Cold Environments: The Sediment‐Availability‐Transport (SAT) Model

“…To include the antecedent precipitation and the time‐lag of response, the correlation between 2‐day average precipitation and SSC is also investigated, but only a limited improvement is found ( R 2 = 0.38; Figure S5c in Supporting Information ). In Tuotuohe station, the precipitation during the melt season is dominated by rainfall (over 90%; Li et al., 2021a). The impact of precipitation on sediment transport can be complicated by the inconsistent time‐lags of sediment response during or right after different rainfall intensities and the spatial heterogeneousness of rainfall events.…”

“…Normally, hydrological variables are observed once a day, while they are observed more frequently (e.g., four times a day) during flood events to capture more likely high sub-daily variations. Detailed strategies and potential uncertainties of discharge and SSC measurements in the Tuotuohe station can be found in Li et al (2021a).…”

“…The mean annual temperature and mean total annual precipitation are −3.4°C and 298 mm respectively, and the basin experiences a melting season from May to September. Ninety‐five percent of the annual precipitation falls between May and October (Figure 1d), when over 90% of precipitation is contributed by rainfall (Li et al., 2021a). Specifically, snowmelt mainly occurs in spring (May–June) and autumn (e.g., September), with two peaks in June and September (Wang et al., 2015).…”

Tibetan Dust Accumulation Linked to Ecological and Landscape Response to Global Climate Change

“…Internal, proximal sources of the loess in the TP contrast with external and distal sources for the CLP from upwind arid basins, gobi and sandy lands in northwest China. During climatic warming periods such as the beginning of the Holocene, permafrost thawing in parts of the TP could have increased ecosystem productivity and vegetation cover while also increased erosion rates and stream sediment loads (Li et al., 2021), both potentially favoring dust production and loess accumulation. In contrast, in the CLP, vegetation density in the dust sink is a less important limiting factor for accumulation.…”

Contrasting Impacts of a Hotter and Drier Future on Streamflow and Catchment Scale Sediment Flux in the High Andes

“…These regions are uniquely sensitive to hydroclimatological changes due to the important contributions of glaciers, snow, and other cryoforms to fluvial sediment transport networks and the regulation of these processes by air temperature (East & Sankey, 2020; Hirschberg et al., 2021; Wulf et al., 2012). While efforts to quantify the impacts of climate change on sediment fluxes from mountainous and higher altitude regions have increased in recent years (e.g., Hirschberg et al., 2021; D. Li et al., 2020, 2021; Wulf et al., 2012), efforts to understand these processes in the high Andes Mountains of Argentina and Chile are still relatively sparse (e.g., Carrillo & Mao, 2020).…”