Large closed-basin lakes sustainably supplied phosphate during the origins of life

American Association for the Advancement of Science (AAAS) | February 19th, 2025

The origin of life on Earth required a supply of phosphorus (P) for the synthesis of universal biomolecules. Closed lakes may have accumulated high P concentrations on ea

The origin of life on Earth required a supply of phosphorus (P) for the synthesis of universal biomolecules. Closed lakes may have accumulated high P concentrations on early Earth. However, it is not clear whether prebiotic P uptake in such settings would then have been sustainable. We show that large closed-basin lakes can combine high P concentrations at steady state with extremely high rates of biological productivity. Our case study is Mono Lake in California, which has close to 1 millimolar dissolved P at steady state despite extremely high rates of biological productivity, in contrast to smaller closed basins where life is scarce. Hence, large closed-basin lakes offer an environment where high rates of prebiotic P productivity can plausibly coexist with high steady-state P concentrations. Such lakes should have readily formed on the heavily cratered and volcanically active surface of early Earth.

Large contribution from anthropogenic warming to an emerging North American megadrought

American Association for the Advancement of Science (AAAS) | April 17th, 2020

Severe and persistent 21st-century drought in southwestern North America (SWNA) motivates comparisons to medieval megadroughts and questions about the role of anthropogen

Severe and persistent 21st-century drought in southwestern North America (SWNA) motivates comparisons to medieval megadroughts and questions about the role of anthropogenic climate change. We use hydrological modeling and new 1200-year tree-ring reconstructions of summer soil moisture to demonstrate that the 2000–2018 SWNA drought was the second driest 19-year period since 800 CE, exceeded only by a late-1500s megadrought. The megadrought-like trajectory of 2000–2018 soil moisture was driven by natural variability superimposed on drying due to anthropogenic warming. Anthropogenic trends in temperature, relative humidity, and precipitation estimated from 31 climate models account for 47% (model interquartiles of 35 to 105%) of the 2000–2018 drought severity, pushing an otherwise moderate drought onto a trajectory comparable to the worst SWNA megadroughts since 800 CE.

Large global-scale vegetation sensitivity to daily rainfall variability

Nature Portfolio (Springer Nature) | December 11th, 2024

Click here for a plain language summary from NASA.

Click here for a plain language summary from NASA.

Large Landscape Urban Irrigation: A Data‐Driven Approach to Evaluate Conservation Behavior

American Geophysical Union (AGU) | April 30th, 2019

Do businesses, multifamily residences, and homeowners associations irrigate differently than single‐family residences? Do customers who have recycled water irrigate di

Do businesses, multifamily residences, and homeowners associations irrigate differently than single‐family residences? Do customers who have recycled water irrigate differently than if they have potable water? How does water use change during drought and under different policy regimes? Is neighborhood affluence related to conservation behavior by nonresidential irrigation customers? These questions are all important for water managers planning how much water they need when and where, in the present and in the future. In this paper, we statistically investigated and modeled water use in a case study service area to examine how water demand for nonresidential large landscapes changed during a historic drought. The findings of this paper can help water managers understand urban water use behavior, which is useful for supply planning, targeting conservation efforts, and optimizing infrastructure investment.

Large Landscape Urban Irrigation: A Data‐Driven Approach to Evaluate Conservation Behavior

American Geophysical Union (AGU) | January 30th, 2019

Do businesses, multifamily residences, and homeowners associations irrigate differently than single‐family residences? Do customers who have recycled water irrigate di

Do businesses, multifamily residences, and homeowners associations irrigate differently than single‐family residences? Do customers who have recycled water irrigate differently than if they have potable water? How does water use change during drought and under different policy regimes? Is neighborhood affluence related to conservation behavior by nonresidential irrigation customers? These questions are all important for water managers planning how much water they need when and where, in the present and in the future. In this paper, we statistically investigated and modeled water use in a case study service area to examine how water demand for nonresidential large landscapes changed during a historic drought. The findings of this paper can help water managers understand urban water use behavior, which is useful for supply planning, targeting conservation efforts, and optimizing infrastructure investment.

Large-Scale Environments of Successive Atmospheric River Events Leading to Compound Precipitation Extremes in California

American Meteorological Society (AMS) | February 18th, 2022

Successive atmospheric river (AR) events—known as AR families—can result in prolonged and elevated hydrological impacts relative to single ARs due to the lack of reco

Successive atmospheric river (AR) events—known as AR families—can result in prolonged and elevated hydrological impacts relative to single ARs due to the lack of recovery time between periods of precipitation. Despite the outsized societal impacts that often stem from AR families, the large-scale environments and mechanisms associated with these compound events remain poorly understood. In this work, a new reanalysis-based 39-yr catalog of 248 AR family events affecting California between 1981 and 2019 is introduced. Nearly all (94%) of the interannual variability in AR frequency is driven by AR family versus single events. Using k-means clustering on the 500-hPa geopotential height field, six distinct clusters of large-scale patterns associated with AR families are identified. Two clusters are of particular interest due to their strong relationship with phases of El Niño–Southern Oscillation (ENSO). One of these clusters is characterized by a strong ridge in the Bering Sea and Rossby wave propagation, most frequently occurs during La Niña and neutral ENSO years, and is associated with the highest cluster-average precipitation across California. The other cluster, characterized by a zonal elongation of lower geopotential heights across the Pacific basin and an extended North Pacific jet, most frequently occurs during El Niño years and is associated with lower cluster-average precipitation across California but with a longer duration. In contrast, single AR events do not show obvious clustering of spatial patterns. This difference suggests that the potential predictability of AR families may be enhanced relative to single AR events, especially on subseasonal to seasonal time scales.

Late Cenozoic Tectonism of the Sacramento Valley, California

U.S. Geological Survey (USGS) | July 15th, 1987

Late Holocene Lacustrine Chronology and Archaeology of Ancient Lake Cahuilla, California

Quaternary Research (Elsevier) | May 1st, 1983

Freshwater lakes existed intermittently in the Salton Trough of southern California during the late Holocene. The lakes formed north of the subaerial Colorado River Delta

Freshwater lakes existed intermittently in the Salton Trough of southern California during the late Holocene. The lakes formed north of the subaerial Colorado River Delta whenever the Colorado River flowed west into the trough instead of south to the Gulf of California. Water filled the trough to a maximum altitude of 12 m. Stratigraphy, radiocarbon dates, and supplementary evidence document four lacustral intervals of Lake Cahuilla between A.D. 700 and 1580. Archaeological sites are associated with the 12-m shoreline and their occupation correlates with these lacustral intervals.

Late Pleistocene exploration and settlement of the Americas by modern humans

American Association for the Advancement of Science (AAAS) | June 12th, 2019

North and South America were the last continents to be explored and settled by modern humans at the end of the Pleistocene. Genetic data, derived from contemporary popul

North and South America were the last continents to be explored and settled by modern humans at the end of the Pleistocene. Genetic data, derived from contemporary populations and ancient individuals, show that the first Americans originated from Asia and after several population splits moved south of the continental ice sheets that covered Canada sometime between ~17.5 and ~14.6 thousand years (ka) ago. Archaeological evidence shows that geographically dispersed populations lived successfully, using biface, blade, and osseous technologies, in multiple places in North and South America between ~15.5 and ~14 ka ago. Regional archaeological complexes emerged by at least ~13 ka ago in North America and ~12.9 ka ago in South America. Current genetic and archaeological data do not support an earlier (pre–17.5 ka ago) occupation of the Americas.

Latitudinal gradients of snow contamination in the Rocky Mountains associated with anthropogenic sources

Elsevier | March 26th, 2025

Seasonal snow is an important source of drinking water and recreation, and for agriculture in the Rocky Mountain region. Monitoring snow-water quality can inform on the e

Seasonal snow is an important source of drinking water and recreation, and for agriculture in the Rocky Mountain region. Monitoring snow-water quality can inform on the effects to the albedo and energy balance of the snowpack, and the sources of natural and anthropogenic aerosol and gases. This study analyzed metals in the seasonal snowpack from water year (WY) 2018 for 49 sites. Calcium, lanthanum, and cerium concentrations support the importance of mineral dust to the southern Rocky Mountains. Mercury (Hg), zinc (Zn), and cadmium (Cd) concentrations showed a similar spatial pattern to mineral dust, whereas antimony (Sb) concentrations were highest in the northern Rocky Mountains. To assess the relative contributions from dust versus anthropogenic contaminant sources, enrichment factors (EF) were calculated, with values above 10 indicating anthropogenic contamination. For Cd, Hg, Sb, and Zn, EF values exceeded 10 at northern sites. These observations were compared to spatial trends of EF values of Hg from WY2009 to WY2018, regional monitoring networks, and back trajectory analyses. The agreement between these datasets revealed temporally consistent contaminant sources and/or transport processes to the northern Rocky Mountains snowpack. Sources include current and historical mining and smelting in the region. Strategies to limit the emissions of these metals to the Northern Rockies could benefit from focusing on remediation of contaminated sites, and continued monitoring and mitigation of active mining and smelting.