Jakob Heyman

Glacial geomorphology of the Tian Shan

The glacial geomorphology of the Tian Shan has been mapped, with the study area covering almost 638,000 km2. The map, designed to be printed at A0 size due to the elongated shape of the mountain range, is presented at a scale of 1:1,100,000. Five glacial landform categories are presented; glacial valleys, marginal moraines, glacial lineations, hummocky terrain and meltwater channels. These landform categories were mapped using the Shuttle Radar Topography Mission (SRTM) digital elevation model (90 m resolution), Landsat 7 ETM+ satellite imagery (30 m resolution), and images contained in Google Earth. The mapped landforms were created by glaciers that were restricted to mountain areas and their immediate surroundings.

Glacial geomorphology of the Shaluli Shan area, southeastern Tibetan Plateau

We present a glacial geomorphological map covering 1.04 × 105 km2 of the Shaluli Shan (Shan = Mountain), southeastern Tibetan Plateau. Using a 90 m digital elevation model from the Shuttle Radar Topography Mission and 15/30 m Landsat Enhanced Thematic Mapper Plus satellite imagery, we have mapped glacial valleys, marginal moraines, hummocky terrain, glacial lineations and ice-scoured terrain. Lineations and scoured areas largely overlap on the low relief granite plateau of the Shaluli Shan and relate to former ice cap glaciation. These landscape features indicate that past ice cap glaciation included basal sliding conditions, and thus warm-based ice. Glacial valleys and marginal moraines are dominant landforms in the high mountain ranges of Shaluli Shan and occur on and fringing the plateau. This glacial geomorphological map forms the basis for paleoglaciological reconstructions of this southeastern Tibetan Plateau region and indicates the former presence of multiple glaciations involving valley glaciers and ice caps. The map is presented at a scale of 1:630,000.

Inner gorges cut by subglacial meltwater during Fennoscandian ice sheet decay

The century-long debate over the origins of inner gorges that were repeatedly covered by Quaternary glaciers hinges upon whether the gorges are fluvial forms eroded by subaerial rivers, or subglacial forms cut beneath ice. Here we apply cosmogenic nuclide exposure dating to seven inner gorges along ~500 km of the former Fennoscandian ice sheet margin in combination with a new deglaciation map. We show that the timing of exposure matches the advent of ice-free conditions, strongly suggesting that gorges were cut by channelized subglacial meltwater while simultaneously being shielded from cosmic rays by overlying ice. Given the exceptional hydraulic efficiency required for meltwater channels to erode bedrock and evacuate debris, we deduce that inner gorges are the product of ice sheets undergoing intense surface melting. The lack of postglacial river erosion in our seven gorges implicates subglacial meltwater as a key driver of valley deepening on the Baltic Shield over multiple glacial cycles.