The climatic, hydrographic, and environmental regimes of terminal Pleistocene and Holocene northwestern Mongolia are reconstructed using archaeological and pedological data sets at Bayan Nuur, a lake on the northwestern perimeter of the Altan Els dune field in eastern Uvs Province, Mongolia. The archaeological data consist of land-use patterns controlled for time via time-sensitive, diagnostic artifacts. The pedological data consist of soil classifications and radiocarbon dating of paleosols that track lake levels and water table. These data are combined using a geographic information system (GIS) to ascertain site and paleosol geographic relationships to modern lake levels at Bayan Nuur. They point to a more xeric Younger Dryas than previously recognized, significant Holocene lake regressions, and to Mid- to Late Holocene lake standstills/transgressions, the scale of which had previously been unrecognized. Combined, these data point to a complex late Quaternary picture of paleoclimate and paleoenvironment across the region and the importance of using multiple proxies, including archaeological data, in paleoecological reconstructions.

Bubiyan Island, presently a vast sabkha and salt flat in the westernmost part of the Shatt Al-Arab delta, originated ca. 4000 cal yr BP as prodelta deposits from a paleochannel of the Euphrates River that flowed into a shallow sea. Southeastern Bubiyan Island first surfaced when spits and barrier islands formed on a 1–2 m forebulge caused by heavy sediment load to the northwest; the spits and barriers delineated an incipient shoreline and sheltered a shallow lagoon. Progradation of southeastern Bubiyan Island began when the spits and barriers were gradually stranded as beach ridges during minor sea-level fluctuations and continued marginal uplift. AMS dating of the beach ridges, which are ~1–5 km from the present shoreline, implies that Late Holocene relative sea level fell in three phases: ca. 3700–3400 cal yr BP, ca. 2600–1000 cal yr BP, and ca. 600–500 cal yr BP. Prior to each phase, relative sea level apparently stabilized to near stillstands, allowing spits and barriers to accrete. Torpedo-jar pottery sherds scattered on some of the most prominent beach ridges indicate Sasanian (AD ca. 300–650; 1650–1300 cal yr BP) to early Islamic (AD ca. 650–800; 1300–1150 cal yr BP) periods of human presence, concurrent with the Second phase of beach-ridge formation.

The 4.2 ka event is widely presumed to be a globally widespread aridity event and has been linked to several episodes of societal changes across the globe. Whether this climate event impacted the cultural development in south-central China remains uncertain due to a lack of regional paleorainfall records. We present here stalagmite stable carbon isotope and trace element–based reconstruction of hydroclimatic conditions from south-central China. Our data reveal a sub–millennial scale (~5.6 to 4.3 ka) drying trend in the region followed by a gradual transition to wetter conditions during the 4.2 ka event (4.3–3.9 ka). Together with the existing archaeological evidence, our data suggest that the drier climate before 4.3 ka may have promoted the Shijiahe culture, while the pluvial conditions during the 4.2 ka event may have adversely affected its settlements in low-lying areas. While military conflicts with the Wangwan III culture may have accelerated the collapse of Shijiahe culture, we suggest that the joint effects of climate and the region's topography also played important causal roles in its demise.

The history of past hydroclimatic extreme events, essential information for predicting future changes, is preserved in fluvial sediments. Here, we reconstruct changes in decadal-scale extreme flooding events over the period 7700–1700 cal yr BP from floodplain sediments in the middle reach of the Nakdong River, Korea, based on lithogenic elemental ratios (e.g., Zr/Ti and Sr/Si). For example, Nakdong extreme flooding (NEF) events frequently occurred at 7700, 7200, 6000, 5000, 3800, 3200, 2900, 2600, 2300, 2000, and 1700 cal yr BP, and were associated with higher sea-surface temperatures and strong El Niño-Southern Oscillation (ENSO) activity. Notably, we found a significant change in the frequency of extreme events ca. 3700 cal yr BP over East Asia. The hydroclimate fluctuated with dominant periodicities of 950 and 540 years in 7700–3700 cal yr BP and shorter centennial to decadal cycles (320, 110–120, and 60–75 years) in 3700–1700 cal yr BP. This 3.7-ka climatic shift is consistent with a marked southward shift of the intertropical convergence zone, intensified ENSO activity, increased frequency of recurving typhoons, and deep-ocean circulation changes in both the northern and southern hemispheres, demonstrating the urgent need for investigating the critical role of past deep-water circulation in hydroclimate changes.

The late Holocene Bonneville landslide, a 15.5 km2 rockslide-debris avalanche, descended 1000 m from the north side of the Columbia River Gorge and dammed the Columbia River where it bisects the Cascade Range of Oregon and Washington, USA. The landslide, inundation, and overtopping created persistent geomorphic, ecologic, and cultural consequences to the river corridor, reported by Indigenous narratives and explorer accounts, as well as scientists and engineers. From new dendrochronology and radiocarbon dating of three trees killed by the landslide, one entrained and buried by the landslide and two killed by rising water in the impounded Columbia River upstream of the blockage, we find (1) the two drowned trees and the buried tree died the same year, and (2) the age of tree death, and hence the landslide (determined by combined results of nine radiocarbon analyses of samples from the three trees), falls within AD 1421–1455 (3σ confidence interval). This result provides temporal context for the tremendous physical, ecological, and cultural effects of the landslide, as well as possible triggering mechanisms. The age precludes the last Cascadia Subduction Zone earthquake of AD 1700 as a landslide trigger, but not earlier subduction zone or local crustal earthquakes.

A unique regional climate progression, ca 14.2–11.5 cal ka BP, in the eastern Great Lakes region of North America is suggested by subfossil logs, high-resolution 14C dates, and established proxy records in New York, USA. The progression began with a northern boreal-type climate ca. 14.2–13.1 ka coeval with the expansion of Lake Iroquois, a transition to a southern boreal-type climate ~13.1–12.9 ka that coincided with the transition of Lake Iroquois into progressively lower lake levels, and a continuation of the southern boreal-type climate ~12.9–11.5 ka. These conditions and changes are evident in the tree rings and relative dominance of tamarack (Larix laricina) and spruce species (Picea spp.) plus the presence of black ash (Fraxinus nigra) as the only thermophilous species. Together they suggest variations in atmospheric moisture levels, surface winds, temperature extremes, and/or an enhanced seasonality over time. Here we propose that the evolution of the glacial Great Lakes and their interactions with ice sheets, meltwater, winds, and regional topography created a regional glacial lake-effect climate, 14.2–11.5 cal ka BP, that was opposite to the established warming Bølling-Allerød–cold Younger Dryas climate progression.

The Salinas del Bebedero occupies an isolated basin in the foreland of central Argentina at 33°S and was flooded repeatedly over past 25 ka. Isotopic evidence demonstrates that this flooding was due to overflow of the nearby Río Desaguadero with waters derived from the distant (≥300 km) central Andes between 28–34°S. Stratigraphic and shoreline evidence shows that floods occurred most frequently from 14.3 to 11.4 ka, followed by lesser events between 14.3 to 11.4 ka, and during the late Holocene from 2.6 to ca. 0.2 ka. Hydraulic modeling (2D HEC-RAS) shows that these floods could have originated from repeated subglacial drainage or sudden outbursts with a volume of >100 × 106 m3 and a peak discharge of >1,000 m3 s-1 each. The absence of flood deposits from 11 to 3 ka points to exceptionally dry and virtually ice-free conditions in the Andes between 28–34°S. The floods were probably caused by major rainfall or dammed-lake outbursts clustered largely during wet pluvial periods in the otherwise moisture-limited central Andes and Atacama Desert, such as when the Intertropical Convergence Zone was shifted southward. These include Central Andean pluvial events (CAPE) I (17–14.5 ka) and II (12.5–9 ka), and the Neoglacial/Formative archeological period 2500 ka to near-present.

Topographic diffusivity is an often-used metric of regolith mobility. It accounts for the collective effects of climate, substrate, fauna, flora, and other factors on hillslope degradation and is used to model natural lowering in landscapes. The present study assesses where temporal variations in diffusivity derived from known past climate fluctuations have occurred. We also determine where significant differences might result when modeling landscape degradation if a long-term constant diffusivity is applied instead of diffusivity that varies through time. A space-for-time substitution approach was implemented. Through use of a transfer function that correlates current diffusivities with air temperatures, we mapped the relative diffusivities globally at a 500 yr temporal resolution for 21 ka. The analyses spanned all land areas from the tropics to the poles with a spatial resolution of 3.70° latitude by 3.75° longitude using paleo-temperature data from the TraCE-21ka global paleoclimate model. The results show Arctic and subarctic regions with the highest relative maximum diffusivities and largest variance from current values. The results suggest strong surficial dynamics in the Arctic and subarctic regions driven by local and spatially transient deglaciation and long-term stability in the tropics that correlates with relatively stable climate there through the past 21 ka.

Stable isotopes are a powerful tool for reconstructing the past. However, environmental factors not previously considered can lead to misinterpretations. Our study presents a novel analysis of the feeding behavior of the megafauna that inhabited the Pilauco ecosystem in south-central Chile during the last glacial termination. We analyzed a suite of modern plant and animal samples from closed-canopy forests to establish an isotopic baseline with which to compare stable isotope results from fossil megafauna. Using the modern samples as a reference, the δ13C results from the Pilauco megafauna indicate feeding behaviors in forested areas. These results were then calibrated with dental calculus samples and coprolites, which suggest the coexistence of graze- and grass-dominated mixed-feeder diets. The δ15N values found in Pilauco megafauna are not consistent with modern reference data sets or with the low δ15N values of extinct proboscideans from other contemporaneous and nearby sites. Probably, the δ15N values of the Pilauco ecosystem were not primarily affected by climate, but rather by disturbance factors (e.g., grazing effect). Our results indicate that the Pilauco megafauna fed mainly on arboreal vegetation; however, non-isotopic proxies indicate that they were also eating open vegetation (e.g., herbs and grasses).

This paper describes the results of research at Volchia Griva, the largest site in Asia containing mammoth fauna in situ. It is situated in the south of the West Siberian Plain in the Baraba forest-steppe zone, and occupies an area of several hectares. Analysis of sediments and taphonomy of the site allows us to suggest that thousands of megafaunal remains were buried here in mud pits and erosional depressions. The favorable geochemical landscape of Volchia Griva attracted animals during periods of mineral starvation. This is reflected in the high mortality in two intervals, ca. 20–18 14C ka BP and ca. 17–11 14C ka BP. The results of palynological analysis of samples from the upper part of the Volchia Griva section made it possible to reconstruct the history of landscape changes of the Baraba Lowland during the MIS 2. Forb-mesophytic meadows were common at the beginning of this period, with taiga type forests. At ca. 20 14C ka BP, an abrupt and significant aridization of the climate occurred, which led to the degradation of forests. The mammoth steppe was widely developed, dominated by forb-grass association and with areas of alkali meadows and soils. Such conditions existed probably until the mid-Holocene.

We use PRISM climatic data (1981–2010) and Landsat images (2012–2013) to establish an empirical relationship linking annual temperature and precipitation to the equilibrium line altitude (ELA) of glaciers in the Sierra Nevada (36–41°N, California, USA). For this, we determined the present-day ELAs of 57 glaciers and the local 0°C isotherms elevation Iso0, averaged over the 1981–2010 period. The difference, for each glacier, is Y, the normalized snowline altitude (Y = ELA – Iso0). We then empirically calibrated a logarithmic relationship between this normalized snowline altitude and mean annual precipitation using data from partially covered glaciers. Our calibration is statistically distinct from that previously established for the tropical and midlatitude Andes (Fox and Bloom [1994], Journal of Geography (Chigaku Zasshi), 103, 867–885; Condom et al. [2007], Global and Planetary Change, 59, 189–202). This new relationship for North America is an easy-to-use tool to permit paleoclimatic reconstructions from paleo-ELAs. For a specific paleoglacial site, paleotemperature can be computed knowing the paleoprecipitation range, and vice versa. We also performed a test showing that, if precipitation is well known, the uncertainty associated with paleotemperature is about 1°C (1σ).

A multidecadal-resolved stalagmite δ18O record from two nearby caves, Lianhua and Dragon, in Shanxi Province, northern China, characterizes the detailed East Asian summer monsoon (EASM) intensity changes at 114.6–108.3 ka during Marine Oxygen Isotope Stage 5d. Our record shows an intensification of the EASM at 114.6–109.5 ka, followed by a rapid weakening at 109.5–108.4 ka. The millennial-scale strong monsoonal event appears to be correlated with the warm Greenland interstadial 25 (GI 25), whereas the weak monsoonal event is related to the cold Greenland stadial 25 within dating errors. The GI 25 monsoonal event registered in our record is also documented in various published time series from different regions of China. The lines of evidence indicate that this event occurred over the entirety of monsoonal China and was also broadly antiphase, similar to the corresponding event on a millennial time scale in the South American monsoon territory. In our record, one 700 yr weak monsoon event at 110.7+0.6−0.5 to 110.0+0.8−0.4 ka divides the GI 25 into three substages. These multicentennial to millennial–scale monsoon events correspond to two warm periods and an intervening cold interval for the intra-interstadial climate oscillations within GI 25, thus supporting a persistent coupling of the high- and low-latitude climate systems over the last glacial period.