Continental-scale patterns of morphological and biological change represent broad time- and spatially averaged interpretations. Conversely, regionally focused studies of morphological variability offer an opportunity to consider patterns of biological change at more refined spatial scales, where nuanced histories may be identified. That approach is particularly applicable for areas known to have dynamic biogeographic and glacial landscapes (e.g., western Canada). We studied proboscideans from Alberta, Canada, an area thought to represent a zone of sympatry between extinct forms of mammoth (i.e., Mammuthus columbi, Mammuthus primigenius) in order to test existing taxonomic hypotheses and chronologically contextualize the regional record of mammoths through the Late Pleistocene. Morphometric analysis of sixth molars of mammoths from Alberta (n = 17) support identification of three distinct morphologies that we assign to M. columbi, M. primigenius, and intermediates of those taxa. The presence of intermediate forms is perhaps unsurprising, given both the recognition of hybridization in M. columbi and M. primigenius and the previously documented occurrence of both taxa in Alberta. Some records of M. columbi may document a broader northern geographic incursion for that taxon than previously recognized, but could also represent a much deeper time component to the history of Mammuthus in Alberta (i.e., Mammuthus trogontherii).

As historic drought conditions become more common in western North America, Late Quaternary hydroclimate records become vital for putting present anthropogenic conditions into a longer-term context. Here, we establish a high-resolution record of drought for the eastern Sierra Nevada (California) using lacustrine carbonates from well-dated sediment cores. We used oxygen and carbon stable-isotope ratios, combined with high-resolution scanning X-ray fluorescence counts of calcium (Ca) and titanium (Ti), to reconstruct the drought record over the last 4600 years in June Lake. We found elevated δ18O and δ13C carbonate isotope values coinciding with peaks in both total inorganic carbon and Ca/Ti, suggesting enhanced carbonate precipitation in response to evaporative concentration of lake water. At least six intervals of prolonged (centennial-scale) carbonate deposition were identified, including three pulses during the Late Holocene Dry Period (LHDP; ~3500–2000 cal yr BP), the Medieval Climate Anomaly (~1200–800 cal yr BP), and the Current Warm Period, which began around 100 cal yr BP. This record highlights the complexities of the LHDP, an interval that was more variable at June Lake than has been previously described in regional records.

The cause of megafauna extinction in South America remains clouded in controversy, since it took place at a time of intense climate change and almost at the same time as the initial human influx into the continent. In this paper, we aimed to assess the effects of climate change on open vegetation habitats and, consequently, on megafauna extinction in South America by using a species distribution model, fossil records, and paleoclimatic projections. In addition, we evaluated the effects of climatic variables on the distribution of suitable habitats across South America. Our results demonstrated alternating intervals of expansion and contraction of suitable areas for megafauna persistence, mainly in response to lower and higher precipitation, in the last 21 ka in all regions of South America. However, the amplitude of this oscillation was more significant in the Brazilian Northeast. In the Andean and Chaco–Pampas regions, greater precipitation stability resulted in greater stability in habitat suitability; therefore, for these regions, other factors must have predominated for the extinction of the megafauna. We therefore concluded that in the Andean and Chaco–Pampas regions, climate change was not solely responsible for the disappearance of megafauna, but in the Brazilian Northeast, it may have been decisive.

Lake sediment provides a valuable record of past environmental change. However, the controls on sedimentation in proglacial lakes and their relation to glacier retreat remain poorly understood. In this study we analyze glaciolacustrine sediment production and deposition in Canal de los Témpanos, Lago Argentino, Argentine Patagonia. We associate temporal changes in the sedimentologic and geochemical characteristics analyzed from Lago Argentino cores with Late Holocene fluctuations of the Perito Moreno and Ameghino glaciers. We show that the dominant sediment source at our study site switched from Ameghino to Perito Moreno Glacier after the recession of Ameghino Glacier and the formation of the marginal ice-contact lake into which it currently calves. Spectacular ice-dam rupture events generated by Perito Moreno Glacier redistribute large volumes of water through the lake system but do not leave a significant sedimentary signature. Our results demonstrate that a detailed analysis of sedimentologic, petrophysical, and geochemical changes in lake cores can provide insight into regional glacial dynamics and sedimentary processes even in complex systems with multiple competing glacial sources and that changing glacier geometries during retreat can provide insights into the provenience of the sediments.

An understanding of the growth and demise of ice sheets over North America is essential to inform future climate models. One poorly studied subject is the glacial dynamics during interstadial Marine Isotope Stage (MIS) 3 (57–29 ka). To better constrain the southern margin of the Laurentide Ice Sheet during this time period, we re-examined a stratigraphic sequence in southeast Manitoba, Canada, and provide robust evidence for advance and retreat of ice. Around 46.6 ± 5.1 ka (1σ error), fluvial sands were deposited under similar precipitation and significantly cooler summer temperatures than present-day. Ice then advanced south over the area, before retreating once again and a return to boreal forest and grassland conditions. The area was then covered by proglacial Lake Vita, dammed by ice to the north. Geochronology constraints indicate Lake Vita existed from ca. 44.3 ± 3.6 to 30.4 ± 2.3 ka (1σ error), although gaps in the optical and finite radiocarbon ages suggest either a lack of data or plausible temporary ice-margin advances during this time period. Ice covering most of Manitoba during MIS 3 is in line with global δ18O records, and glacially influenced sediment deposition in the Mississippi River basin.

Recent research on the Bering Glacier forelands in the northern Gulf of Alaska provides new insights into late Pleistocene/early Holocene shorelines, providing a favorable route for human migration as early as ~16,000 cal yr BP. This route included an irregular coastline with embayments and islands offering protection from the open ocean; edible marine invertebrates dating from 15,000 to 5,500 cal yr BP; and marine vertebrates dating as early as 16,000 cal yr BP. The latter included walrus (Odobenus rosmarus), bearded seal (Erignathus barbatus), and ringed seal (Phoca cf. hispida), all associated with pack ice conditions unlike those present today. While this ecosystem could have supported humans migrating along the coastline, and coastal refugia may have existed elsewhere in the region, coastal archaeological sites in the northern Gulf of Alaska and southwest Alaska are no older than ~9,500 cal yr BP. This suggests that the earliest sites have been eroded or destroyed, that the earliest migrants ignored available marine resources, and/or that these migrants did not use a coastal route. In contrast, the earliest archaeological sites in southeast Alaska date to ~12,500 cal yr BP, suggesting migration from interior Alaska to the coast somewhere east of the Copper River delta.