This paper examines the hydroclimate history of the Eastern Mediterranean (EM) region during the 10th to 14th centuries C.E., a period known as the Medieval Climate Anomaly (MCA), a time of significant historical turmoil and change in the region. The study assembles several regional hydroclimatic archives, primarily the Dead Sea reconstructed lake level curve together with the recently extracted deep-lake sediment record, the Soreq Cave speleothem record and its counterpart, the EM marine sediment record and the Cairo Nilometer record of annual maximum summer flood levels in lower Egypt. The Dead Sea record is a primary indicator of the intensity of the EM cold-season storm activity while the Nilometer reflects the intensity of the late summer monsoon rains over Ethiopia. These two climate systems control the annual rainfall amounts and water availability in the two regional breadbaskets of old, in Mesopotamia and Egypt. The paleoclimate archives portray a variable MCA in both the Levant and the Ethiopian Highlands with an overall dry, early-medieval climate that turned wetter in the 12th century C.E. However, the paleoclimatic records are markedly punctuated by episodes of extreme aridity. In particular, the Dead Sea displays extreme low lake levels and significant salt deposits starting as early as the 9th century C.E. and ending in the late 11th century. The Nile summer flood levels were particularly low during the 10th and 11th centuries, as is also recorded in a large number of historical chronicles that described a large cluster of droughts that led to dire human strife associated with famine, pestilence and conflict. During that time droughts and cold spells also affected the northeastern Middle East, in Persia and Mesopotamia. Seeking an explanation for the pronounced aridity and human consequences across the entire EM, we note that the 10th–11th century events coincide with the medieval Oort Grand Solar Minimum, which came at the height of an interval of relatively high solar irradiance. Bringing together other tropical and Northern Hemisphere paleoclimatic evidence, we argue for the role of long-term variations in solar irradiance in shaping the early MCA in the EM and highlight their relevance to the present and near-term future.
more »
« less
Late Holocene droughts and cave ice harvesting by Ancestral Puebloans
Abstract Water availability for Native Americans in the southwestern United States during periods of prolonged droughts is poorly understood as regional hydroclimate records are scant or contradicting. Here, we show that radiocarbon-dated charcoal recovered from an ice deposit accumulated in Cave 29, western New Mexico, provide unambiguous evidence for five drought events that impacted the Ancestral Puebloan society between ~ AD 150 and 950. The presence of abundant charred material in this cave indicates that they periodically obtained drinking water by using fire to melt cave ice, and sheds light on one of many human–environment interactions in the Southwest in a context when climate change forced growing Ancestral Puebloan populations to exploit water resources in unexpected locations. The melting of cave ice under current climate conditions is both uncovering and threatening a fragile source of paleoenvironmental and archaeological evidence of human adaptations to a seemingly marginal environment.
more »
« less
- Award ID(s):
- 2024248
- NSF-PAR ID:
- 10258180
- Date Published:
- Journal Name:
- Scientific Reports
- Volume:
- 10
- Issue:
- 1
- ISSN:
- 2045-2322
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Human activity and climate change are altering natural rates and intensities of wildfire, but the scale and extent of burning prior to the modern era are poorly understood. Prehistoric fire activity can be reconstructed using a variety of records including charcoal deposited along with sediment at the bottom of lakes and burn scars on tree rings, but these are not available in all environmental settings. We are developing a new paleofire proxy: polycyclic aromatic hydrocarbons (PAHs) in stalagmites. PAHs are produced by the burning of vegetation, with molecular weights reflecting combustion conditions. After being formed in a fire, PAHs are transported downward by infiltrating rainwater and in cave areas can become incorporated into stalagmites as they crystallize from drip water in underlying caves (Perrette et al., 2008; Denniston et al., 2018). Thus, the potential exists for PAHs in stalagmites to preserve evidence of the presence and intensity of fire through time. Because this is a new method, several important tests need to be performed to evaluate its veracity. I assessed how well PAH abundances, ratios, and trends replicate between two coeval stalagmites from cave KNI-51 located in the tropics of Western Australia. Stalagmite KNI-51-F was previously analyzed and I analyzed the overlapping portion of stalagmite KNl-51-G: overlap in age from CE 1310-1630. This work was done at Ca' Foscari University, Venice, in the fall of 2022, under the direction of Dr. Elena Argiriadis. The results show similarities between the area of overlap in the G and F stalagmites. The commonalities of the concentrations of PAH in the stalagmites indicate confidence in the developed method in assessing pyrogenic compounds in coeval stalagmites.more » « less
-
more » « less
Research in Southern Belize has produced a 1000-year record of coupled human and environmental relationships at the ancient Maya city Uxbenká. Located at the southeastern margin of the Maya Lowlands, this region has excellent agricultural land and some of the highest rainfall in the Maya region. Uxbenká was the founding political center in southern Belize after 100 BCE. After 850 years, Uxbenká experienced a long geopolitical disintegration ending in depopulation as part of broad regional collapse. We use kernel density and summed probability distributions of 167 high-precision AMS14C dates to reconstruct relative changes in population and investments in the built environment throughout the growth and decline of the polity. Those data are compared to an annually resolved speleothem paleoclimate record from Yok Balum cave, located less than 3 km from Uxbenká’s civic ceremonial core. With no Classic Period wetland fields or evidence for large-scale landscape investments in agricultural intensification, food production would have been rainfall dependent as was water availability for household use. Using a 30 m SRTM DEM, we compute flow accumulation and the upvalley extents of river networks while varying the input precipitation to reflect hypothesized changes in paleorainfall over time. Our data suggest that Uxbenká experienced rapid growth following a severe drought at 200 CE, as well as cycles of growth and contraction until just after 750 CE. We find that geopolitical disintegration in southern Belize was already underway when a severe drought began at 830 CE. That six-decade drought likely contributed to the abandonment of Uxbenká and limited geopolitical reorganization.
-
more » « less
In the southwestern United States, California (CA) is one of the most climatically sensitive regions given its low (≤250 mm/year) seasonal precipitation and its inherently variable hydroclimate, subject to large magnitude modulation. To reconstruct past climate change in CA, cave calcite deposits (stalagmites) have been utilized as an archive for environmentally sensitive proxies, such as stable isotope compositions (δ18O, δ13C) and trace element concentrations (e.g., Mg, Ba, Sr). Monitoring the cave and associated surface environments, the chemical evolution of cave drip-water, the calcite precipitated from the drip-water, and the response of these systems to seasonal variability in precipitation and temperature is imperative for interpreting stalagmite proxies. Here we present monitored drip-water and physical parameters at Lilburn Cave, Sequoia Kings Canyon National Park (Southern Sierra Nevada), CA, and measured trace element concentrations (Mg, Sr, Ba, Cu, Fe, Mn) and stable isotopic compositions (δ18O, δ2H) of drip-water and for calcite (δ18O) precipitated on glass substrates over a two-year period (November 2018 to February 2021) to better understand how chemical variability at this site is influenced by local and regional precipitation and temperature variability. Despite large variability in surface temperatures and precipitation amount and source region (North Pacific vs. subtropical Pacific), Lilburn Cave exhibits a constant cave environment year-round. At two of the three sites within the cave, drip-water δ18O and δ2H are influenced seasonally by evaporative enrichment. At a third collection site in the cave, the drip-water δ18O responds solely to precipitation δ18O variability. The Mg/Ca, Ba/Ca, and Sr/Ca ratios are seasonally responsive to prior calcite precipitation at all sites but minimally to water-rock interaction. Lastly, we examine the potential of trace metals (e.g., Mn2+and Cu2+as a geochemical proxy of recharge and find that variability in their concentrations has high potential to denote the onset of the rainy season in the study region. The drip-water composition is recorded in the calcite, demonstrating that stalagmites from Lilburn Cave, and potentially more regionally, could record seasonal variability in weather even during periods of substantially reduced rainfall.
-
Recent excavation in the new CRREL Permafrost Tunnel in Fox, Alaska provides a unique opportunity to study properties of Yedoma — late Pleistocene ice- and organic-rich syngenetic permafrost. Yedoma has been described at numerous sites across Interior Alaska, mainly within the Yukon-Tanana upland. The most comprehensive data on the structure and properties of Yedoma in this area have been obtained in the CRREL Permafrost Tunnel near Fairbanks — one of the most accessible large-scale exposures of Yedoma permafrost on Earth, which became available to researchers in the mid-1960s. Expansion of the new ∼4-m-high and ∼4-m-wide linear excavations, started in 2011 and ongoing, exposes an additional 300 m of well-preserved Yedoma and provides access to sediments deposited over the past 40,000 years, which will allow us to quantify rates and patterns of formation of syngenetic permafrost, depositional history and biogeochemical characteristics of Yedoma, and its response to a warmer climate. In this paper, we present results of detailed cryostratigraphic studies in the Tunnel and adjacent area. Data from our study include ground-ice content, the stable water isotope composition of the variety of ground-ice bodies, and radiocarbon age dates. Based on cryostratigraphic mapping of the Tunnel and results of drilling above and inside the Tunnel, six main cryostratigraphic units have been distinguished: 1) active layer; 2) modern intermediate layer (ice-rich silt); 3) relatively ice-poor Yedoma silt reworked by thermal erosion and thermokarst during the Holocene; 4) ice-rich late Pleistocene Yedoma silt with large ice wedges; 5) relatively ice-poor fluvial gravel; and 6) ice-poor bedrock. Our studies reveal significant differences in cryostratigraphy of the new and old CRREL Permafrost Tunnel facilities. Original syngenetic permafrost in the new Tunnel has been better preserved and less affected by erosional events during the period of Yedoma formation, although numerous features (e.g., bodies of thermokarst-cave ice, thaw unconformities, buried gullies) indicate the original Yedoma silt in the recently excavated sections was also reworked to some extent by thermokarst and thermal erosion during the late Pleistocene and Holocene.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1038/s41598-020-76988-1
