Arctic sea-ice loss drives a strong regional atmospheric response over the North Pacific and North Atlantic on decadal scales

Nature Portfolio (Springer Nature) | March 11th, 2025

Previous studies have suggested that Arctic sea-ice loss can have a profound influence on atmospheric circulation far away from the Arctic. However, there is litt

Previous studies have suggested that Arctic sea-ice loss can have a profound influence on atmospheric circulation far away from the Arctic. However, there is little scientific consensus on the features of these remote responses, with the opposite impacts reported. Here we present a multi-model analysis of the decadal climate response to Arctic sea-ice loss using state-of-the-art energy conserving methodologies to isolate the impacts of sea-ice decline. We observe weakening of the Aleutian Low and development of a geopotential ridge in the North Pacific, associated with drier winter conditions over the southwest United States. Over the Atlantic, a negative NAO-like response drives wetter winter conditions across the western Mediterranean. These decadal-scale impacts substantially differ from reported centennial-scale responses to Arctic sea-ice loss simulated using non-energy conserving methodologies. Factors such as the timescale of the response and methodologies used to isolate the impacts of disappearing sea-ice cover should be carefully considered when consolidating scientific understanding on the future impacts of changing Arctic.

Arctic sea-ice loss is projected to lead to more frequent strong El Niño events

Nature Portfolio (Springer Nature) | August 23rd, 2022

Arctic sea ice has decreased substantially and is projected to reach a seasonally ice-free state in the coming decades. Little is known about whether dwindling Arctic sea

Arctic sea ice has decreased substantially and is projected to reach a seasonally ice-free state in the coming decades. Little is known about whether dwindling Arctic sea ice is capable of influencing the occurrence of strong El Niño, a prominentmode of climate variability with global impacts. Based on time slice coupled model experiments, here we show that no significant change in the occurrence of strong El Niño is found in response to moderate Arctic sea-ice loss that is consistent with satellite observations to date. However, as the ice loss continues and the Arctic becomes seasonally ice-free, the frequency of strong El Niño events increases bymore than one third, as defined by gradientbased indices that remove mean tropical Pacific warming induced by the seasonally ice-free Arctic. By comparing our time slice experiments with greenhouse warming experiments, we conclude that at least 37–48% of the increase of strong El Niño near the end of the 21st century is associated specifically with Arctic sea-ice loss. Further separation of Arctic sea-ice loss and greenhouse gas forcing only experiments implies that the seasonally ice-free Arctic might play a key role in driving significantly more frequent strong El Niño events.

Are Atmospheric Models Too Cold in the Mountains? The State of Science and Insights from the SAIL Field Campaign

American Meteorological Society (AMS) | July 16th, 2024

Are Modern Droughts Unprecedented?

American Geophysical Union (AGU) | August 8th, 2026

Global drought variability of past centuries remains poorly understood due to sparse instrumental records and limited paleoclimate reconstructions. Yet, quantifying long-

Global drought variability of past centuries remains poorly understood due to sparse instrumental records and limited paleoclimate reconstructions. Yet, quantifying long-term forced and unforced variability is key for assessing the extremeness of modern (2000–2024) drought events. Here, we combine 20 ensemble members from a 600-year climate simulation (ModE-Sim, 1420–2009) and modern reanalysis data (ERA5-Land, 1950–2024) to place recent droughts in a multi-century context. Drought magnitude and timing are measured using the annual maximum potential cumulative water deficit (PCWD), which integrates atmospheric moisture demand and supply, the daily timing of precipitation events, snow melt, and radiation. We analyze the deviation of modern annual, multi-year mean, and 30-year extreme PCWD from alternative reference periods that sample forced and unforced variability to a variable extent. We find a strong decline in the number of regions with unprecedented modern (2000–2024) single-year and 25-year mean PCWD as the reference is extended into the past and with the additional consideration of unforced atmospheric variability. This is not the case for extreme droughts. 30-year extreme PCWD has increased beyond the range of variability of the last 600 years in over half of all regions globally. This suggests that drought extremes are intensifying more rapidly beyond the range experienced in the past than mean conditions. While individual droughts in the modern era may not appear unprecedented when viewed against a century-long record, the shift in their frequency distribution indicates a rising risk of damaging impacts and an increasing likelihood of droughts reaching unprecedented magnitudes in the near future.

Areas of Special Biological Significance: California’s Marine State Water Quality Protection Areas

California State Water Resources Control Board (SWRCB) | April 1st, 2008

Designated March 21, 1974 (Resolution No. 74-28), April 18, 1974 (Resolution No. 74-32) and June 19, 1975 (Resolution No. 75-61) This printing of the publication, “A

Designated March 21, 1974 (Resolution No. 74-28), April 18, 1974 (Resolution No. 74-32) and June 19, 1975 (Resolution No. 75-61) This printing of the publication, “Areas of Special Biological Significance, California’s Marine State Water Quality Protection Areas,” replaces and supercedes the January 2003 edition. Changes were made to certain maps, primarily due to the availability of better Geographic Information System (GIS) data. Some of the offshore boundaries of the Areas of Special Biological Significance were adjusted to conform to the State’s three nautical mile (nm) limit.  Maps that were improved or modified are identified as being revised as of June 2003; maps that were not changed are still labeled as being created in January 2003. Assembly Bill 2800, approved by the Governor on September 8, 2000, added sections to the Public Resources Code (PRC) that are relevant to Areas of Special Biological Significance (ASBS). Section 36700 (f) of the PRC defines a state water quality protection area (SWQPA) as “a nonterrestrial marine or estuarine area designated to protect marine species or biological communities from an undesirable alteration in natural water quality, including, but not limited to, areas of special biological significance that have been designated by the State Water Resources Control Board through its water quality control planning process.” Section 36710 (f) of the Public Resources Code states: “In a state water quality protection area point source waste and thermal discharges shall be prohibited or limited by special conditions. Nonpoint source pollution shall be controlled to the extent practicable.” The change of the term Area of Special Biological Significance to State Water Quality Protection Area occurred on January 1, 2003 as required under Section 36750 of the PRC.  The Areas of Special Biological Significance were originally given numerical designations based on the State Water Resources Control Board resolutions in which they were established. These numerical designations are not related to their geographic positions along the coast. Previous editions of this publication (up to and including the 1999 edition) have provided maps of the ASBS in numerical rather than geographic order. For the current edition, maps of Areas of Special Biological Significance/State Water Quality Protection Areas are provided in geographic order from north to south.

Arizona v. California

United States Supreme Court | March 9th, 1964

Arsenic in California Drinking Water

Environmental Integrity Project | September 15th, 2016

More than three years after the U.S. Environmental Protection Agency found California in noncompliance with the federal Safe Drinking Water Act, 95 community water system

More than three years after the U.S. Environmental Protection Agency found California in noncompliance with the federal Safe Drinking Water Act, 95 community water systems in the state, serving more than 55,000 people, are still providing water with illegal levels of arsenic, according to an examination of state data for the last two years. Arsenic occurs naturally in the soil and groundwater in parts of California and is a known carcinogen that may also damage the developing brains of children and cause other health problems. Many of the people drinking excessive levels of arsenic are poor and/or Latino or African- American, with a cluster in the San Joaquin Valley. Nearly all have been exposed to excessive arsenic levels for at least five years and probably longer.

Arsenic, chromium, uranium, and vanadium in rock, alluvium, and groundwater, Mojave River and Morongo Areas, western Mojave Desert, southern California

U.S. Geological Survey (USGS) | October 16th, 2023

Trace elements within groundwater that originate from aquifer materials and pose potential public-health hazards if consumed are known as geogenic contaminants. The geoge

Trace elements within groundwater that originate from aquifer materials and pose potential public-health hazards if consumed are known as geogenic contaminants. The geogenic contaminants arsenic, chromium, and vanadium can form negatively charged ions with oxygen known as oxyanions. Uranium complexes with bicarbonate and carbonate to form negatively charged ions having aqueous chemistry similar to oxyanions. The concentrations of arsenic, chromium, uranium, and vanadium in groundwater result from the combined effects of (1) geologic abundance within aquifer materials; (2) the fraction of these elements that have weathered from and sorbed to the surfaces of mineral grains and are potentially available to groundwater; and (3) the aqueous chemistry of dissolved oxyanions in groundwater during different redox conditions and pH, both of which are affected by hydrogeology, including the length of time groundwater has been in contact with aquifer materials. Concentrations of arsenic, chromium, uranium, and vanadium were measured in samples of (1) rock, surficial alluvium, and drill cuttings using portable (handheld) X-ray fluorescence (pXRF); (2) operationally defined fractions extractable from these materials; and (3) water from wells sampled between 2000 and 2018 within the 3,500 square mile Mojave River area and Morongo area of the western Mojave Desert, southern California.

Arsenic, Chromium, Uranium, and Vanadium in Rock, Arsenic, Chromium, Uranium, and Vanadium in Rock, Alluvium, and Groundwater, Mojave River and Morongo Alluvium, and Groundwater, Mojave River and Morongo Areas, Western Mojave Desert, Southern California

U.S. Geological Survey (USGS) | October 16th, 2023

Trace elements within groundwater that originate from aquifer materials and pose potential public-health hazards if consumed are known as geogenic contaminants. The geoge

Trace elements within groundwater that originate from aquifer materials and pose potential public-health hazards if consumed are known as geogenic contaminants. The geogenic contaminants arsenic, chromium, and vanadium can form negatively charged ions with oxygen known as oxyanions. Uranium complexes with bicarbonate and carbonate to form negatively charged ions having aqueous chemistry similar to oxyanions. The concentrations of arsenic, chromium, uranium, and vanadium in groundwater result from the combined effects of (1) geologic abundance within aquifer materials; (2) the fraction of these elements that have weathered from and sorbed to the surfaces of mineral grains and are potentially available to groundwater; and (3) the aqueous chemistry of dissolved oxyanions in groundwater during different redox conditions and pH, both of which are affected by hydrogeology, including the length of time groundwater has been in contact with aquifer materials. Concentrations of arsenic, chromium, uranium, and vanadium were measured in samples of (1) rock, surficial alluvium, and drill cuttings using portable (handheld) X-ray fluorescence (pXRF); (2) operationally defined fractions extractable from these materials; and (3) water from wells sampled between 2000 and 2018 within the 3,500 square mile Mojave River area and Morongo area of the western Mojave Desert, southern California. ... The quality of water imported from northern California and infiltrated from ponds for groundwater recharge may be altered by naturally present trace elements, especially uranium in areas of agricultural land use or chromium within mafic alluvium. Introduction

Artes: An Integrated Model of Water Supply in L.A. County

University of California, Los Angeles (UCLA) | May 1st, 2017

Los Angeles faces a future with less imported water. Infrastructure and institutions will have to adapt. Understanding emerging policy and investment needs requires anal

Los Angeles faces a future with less imported water. Infrastructure and institutions will have to adapt. Understanding emerging policy and investment needs requires analysis across systems, a typically elusive goal within the diverse and disparately managed water systems of L.A. A more comprehensive analysis of water resources in Los Angeles requires an understanding of people, pipes, and plants. It could also be flexible to incorporate the fast-changing landscape of models, data, and analysis that the active agencies of the region continue to develop. With these goals in mind, we developed a water supply model for the metropolitan L.A. County region (Artes) to understand the potential for enhancing local water use across scenarios of demand and supply. The basic approach combines knowledge from engineering, hydrology, ecology, and sociology. The model is intentionally lightweight. Flexible and adaptive modeling can address many questions at multiple geographic scales, while also being able to incorporate new tools, data, and other models that are released. This model was developed to: * Determine how local groundwater, recycling and stormwater capture supplies could maximally meet water demands across L.A. County, based on current knowledge of hydrology and hydrogeology * Analyze tradeoffs in per capita water demand and available imported water supplies * Investigate system-wide effects of increased conservation * Minimize assumptions regarding data gaps * Use modeling to highlight to key gaps in scientific understanding, while creatively addressing the shortfalls in a precautionary manner. For instance, we compare modeled and historic groundwater pumping and managed aquifer recharge to assess the potential for groundwater overdraft. This manual describes important information for understanding model operations, assumptions, inputs, and outputs. The manual version (3.7) was written after development of 3 versions code for different research studies, which are in press or under review.