Early HoloceneNW‐W winds reconstructed from small dune fields, central Sweden

Abstract

Five small dune fields were investigated in central Sweden in the field and by using LiDAR-based remote sensing. The chronology of the dunes was determined using optically stimulated luminescence (OSL) dating. Most of the OSL ages indicate dune formation close to the time of deglaciation in this area of Sweden (11-10 cal. ka BP) and later sand drift events appear to have been uncommon, suggesting that most of the dune fields have been stable since their formation and throughout the Holocene. This makes them a valuable archive of past sand drift events and palaeowind directions, even though the dune fields are small compared to most other investigated dune fields around the world. The dunes are primarily of a transverse or parabolic type, and their orientation suggests formation by westerly or northwesterly winds. The local topography appears to have had little control over the formation of the dunes, suggesting that the dunes can be used as a proxy of regional wind directions. All dune fields in this study are linked to glacifluvial deposits that provide spatially and volumetrically limited sources of sand.

Age, formation and significance of loess deposits in central Sweden

“…However, as noted in the early studies on Swedish loess highlighted above, the position of the loess deposits poses somewhat of a conundrum (Hjulström et al, 1955). While most central Sweden parabolic dune ridge orientations suggest NW wind directions driving sand movement (Bernhardson & Alexanderson, 2018;Bernhardson et al, 2019), according to previous mapping the loess deposits tend to lie to the south or west of the main dune and glaciofluvial delta and channel areas (Figures 2 and 3), potentially suggesting dust transport by NE winds. This pattern is contrary to what would be expected if the winds that drove dune morphology were the same ones that transported the fine sands, silts and clays that form loess.…”

Sand dunes and valley fills from Preboreal glacial‐lake outburst floods in south‐eastern Norway – beyond the aeolian paradigm

“…Sand dunes in central Sweden contain pipe-like structures interpreted as onshore bioturbation (e.g. Alexanderson et al, 2016;Bernhardson & Alexanderson, 2018;Alexanderson & Bernhardson, 2019). Aeolian dune fields have also been reported from comparable settings in northern Sweden and Finland (Sepp€ al€ a, 2004).…”

Parabolic dune distribution, morphology and activity during the last 20 000 years: A global overview

“…The apparent absence of aeolian deposits before 18 ka BP in the already ice-free proglacial river floodplains could be attributable to permafrost minimising sediment availability (Hilgers, 2007). As ice sheets retreated north, the same conditions prevailed later in Scandinavia (Alexanderson & Bernhardson, 2016;Alexanderson & Fabel, 2015;Bernhardson, 2018;Bernhardson et al, 2019;Bernhardson & Alexanderson, 2018), resulting in a younger phase of parabolic dune build up ($11-7.5 ka BP; Figure 14e).…”

“…The remobilisation of parabolic dunes on the European continent during the late Holocene (Figure 16e) has essentially been attributed to increased storminess during the LIA, Bronze Age, and Late Neolithic (Alexanderson & Bernhardson, 2016;Bernhardson, 2018;Bertran et al, 2011;Clemmensen et al, 2001Clemmensen et al, , 2007De Ceunynck, 1985;Depuydt, 1967;Mäkelä & Illmer, 1990;Tastet, 1998), which were characterised by the expansion of the Polar climate belt and a southward shift of the North Atlantic cyclone track (Borzenkova et al, 2015). Duration and amplitude of these aeolian episodes was probably extended due to increased human pressure on land such as charcoal production and slash-and-burn agriculture in Sweden (Alexanderson & Fabel, 2015;Bernhardson & Alexanderson, 2018), or tree-cutting and cattle breeding in Denmark (Clemmensen et al, 2001). Successive droughts and intensification of F I G U R E 1 5 (a-h) Timelapse of dune activity in North America with respect to the modelled retreat chronology of the Laurentide Ice Sheet (Peltier, 2004) both deforestation and agriculture in the northern European Sand Belt caused the reactivation of parabolic dunes during the MCO (Figure 16e; Bertran et al, 2011;Lungershausen et al, 2018;Tastet, 1998;Tolksdorf & Kaiser, 2012).…”