Can inter-annual climate variability alone explain the glacier retreat since the Little Ice Age in the Hailuogou catchment, southeastern Tibetan Plateau?

Inter-annual climate variability has the potential to induce hundred-to-thousand meters of glacier length change, comparable to the glacier retreats from their Little Ice Age (LIA) positions (Roe and O'Neal, 2009). Distinguishing the roles of inter-annual climate variability and climate change in glacier changes can help us read the true climate signal from the history of glacial activity and provide a basis for detailed attribution of currently observed glacier retreats. Here, we used ArcGIS tools to reconstruct the LIA glacier in the Hailuogou catchment on the southeastern Tibetan Plateau (TP) and calculate the corresponding glacier equilibrium-line altitude (ELA). Based on the LIA ELA, we inferred the climate change supporting the LIA glaciers in the region. Further, we quantified the impact of inter-annual climate variability on the Hailuogou Glacier change using a three-stage linear model. During the LIA, the area of the Hailuogou Glacier was 42.64 km2 and its volume was 3.73 × 109 m3. The LIA ELA was 5068 m above sea level (a.s.l.), lowering by 213 m relatively to the present. The LIA summer temperature was estimated to be ~1.31–2.21 °C colder than the present with the LIA precipitation constraint being 90–100% of the modern precipitation. Forced by the inter-annual variabilities in summer temperature and annual precipitation, the Hailuogou Glacier has a possible maximum negative excursion of 459 m, which can only explain 19.3% of the actual retreat since the LIA. According to the probability density function (PDF) of the modeled length anomalies, the likelihood is <1% for the actual glacier retreat completely due to the inter-annual climate variability. We therefore argued that the inter-annual climate variability alone cannot explain the glacier retreat since the LIA in the Hailuogou catchment. Further, glacier geometry and topography might be the main factors determining the strength of the response of the Hailuogou Glacier to inter-annual climate variability.