Modelling Last Glacial Maximum ice cap with the Parallel Ice Sheet Model to infer palaeoclimate in south‐west Turkey

Abstract

Modelling palaeoglaciers in mountainous terrain is challenging due to the need for detailed ice flow computations in relatively narrow and steep valleys, high-resolution climate estimations, knowledge of pre-ice topography, and proxy-based palaeoclimate forcing. The Parallel Ice Sheet Model (PISM), a numerical model that approximates glacier sliding and deformation to simulate large ice sheets such as Greenland and Antarctica, was recently adapted to alpine environments. In an attempt to reconstruct the climate conditions during the Last Glacial Maximum (LGM) on Mount Dedegöl in SW Turkey, we used PISM and explored palaeoglacier dynamics at high spatial resolution (100 m) in a relatively small domain (225 km 2). Palaeoice-flow fields were modelled as a function of present temperature and precipitation. Nine different palaeoclimate simulations were run to reach the steady-state glacier extents and the modelled glacial areas were compared with the field-based and chronologically wellestablished ice extents. Although our results provide a non-unique solution, best-fit scenarios indicate that the LGM climate on Mount Dedegöl was between 9.2 and 10.6°C colder than today, while precipitation levels were the same as today. More humid (20% wetter) or arid (20% drier) conditions than today bring the palaeotemperature estimates to 7.7-8.8 or 11.5-13.2°C lower than present, respectively.

Simulation of a former ice field with PISM – Snežnik study case

“…PISM 2.0 was installed on several Linux workstations and used throughout the experiments. The modelling parameters of PISM were set identically to those described in Žebre et al (2021), where a larger mountain range just to the South of Snežnik was simulated, and similarly to those in (Candaş et al, 2020), where a similarly sized mountain in Turkey was simulated. That means that most of the parameters were actually left at their default values, which can be found in the official documentation (the PISM authors, 2023).…”

Terrestrial cosmogenic 10Be dating of the Última Esperanza ice lobe moraines (52°S, Patagonia) indicates the global Last Glacial Maximum (LGM) extent was half of the local LGM

“…On the other hand, several studies in the northern hemisphere indicate that gLGM was synchronous in the Alps (Monegato et al, 2017;Seguinot et al, 2018) and most of the Mediterranean region (Hughes and Wood ard, 2017;iner, 2015, 2017). For instance, numerous examples from the eastern Mediterranean (e.g., Sar ka a et al, 2014; K se et al, 2019), eastern Black Sea Mountains of Turkey (Akçar et al, 2007(Akçar et al, , 2008, central Anatolia (Sar ka a et al, 2009;Ak ar et al, 2014), the Caucasus (Dede et al, 2017), Greece (Leontaritis et al, 2020), Dinarids (Çiner et al, 2019Zebre et al, 2019Zebre et al, , 2021Sar ka a et al, 2020), and Corsica (Kuhlemann et al, 2008) show that most of the glaciers were in tune with gLGM and reached their maximum extents in MIS 2, with temperatures dropping between 8 to 11 o C depending on the regions (e.g., Sar ka a et al, 2008Sar ka a et al, , 2009Hughes et al, 2013;Ünal-mer et al, 2015;Canda et al, 2020). Ho e er, t o essential e ceptions come from the Iberian Peninsula and Morocco, where the maximum ice extents were reached between c. 30 and c. 60 ka (Oliva et al, 2019), and c. 50 ka, (Hughes et al, 2018(Hughes et al, , 2020 from MIS 5 to 3, respectively.…”