Showing papers by "Andrew Lorrey published in 2021"
Cooperative Institute for Research in Environmental Sciences1, National Oceanic and Atmospheric Administration2, Met Office3, Oeschger Centre for Climate Change Research4, National Center for Atmospheric Research5, University of Melbourne6, Rovira i Virgili University7, University of East Anglia8, National Research Council9, National Oceanography Centre, Southampton10, University of Zaragoza11, Australian National University12, University of Reading13, Climatic Research Unit14, Hokkaido University15, National Institute of Water and Atmospheric Research16, World Meteorological Organization17, University of South Carolina18, Nicolaus Copernicus University in Toruń19, University of Southern Queensland20, McGill University21, Deutscher Wetterdienst22, Bureau of Meteorology23, Pacific Marine Environmental Laboratory24, University of Washington25
TL;DR: The performance of a new historical reanalysis, the NOAA-CIRES-DOE Twentieth Century Reanalysis version 3 (20CRv3), is evaluated via comparisons with other reanalyses and independent observations as mentioned in this paper.
Abstract: The performance of a new historical reanalysis, the NOAA–CIRES–DOE Twentieth Century Reanalysis version 3 (20CRv3), is evaluated via comparisons with other reanalyses and independent observations. This dataset provides global, 3-hourly estimates of the atmosphere from 1806 to 2015 by assimilating only surface pressure observations and prescribing sea surface temperature, sea ice concentration, and radiative forcings. Comparisons with independent observations, other reanalyses, and satellite products suggest that 20CRv3 can reliably produce atmospheric estimates on scales ranging from weather events to long-term climatic trends. Not only does 20CRv3 recreate a “best estimate” of the weather, including extreme events, it also provides an estimate of its confidence through the use of an ensemble. Surface pressure statistics suggest that these confidence estimates are reliable. Comparisons with independent upper-air observations in the Northern Hemisphere demonstrate that 20CRv3 has skill throughout the twentieth century. Upper-air fields from 20CRv3 in the late twentieth century and early twenty-first century correlate well with full-input reanalyses, and the correlation is predicted by the confidence fields from 20CRv3. The skill of analyzed 500-hPa geopotential heights from 20CRv3 for 1979–2015 is comparable to that of modern operational 3–4-day forecasts. Finally, 20CRv3 performs well on climate time scales. Long time series and multidecadal averages of mass, circulation, and precipitation fields agree well with modern reanalyses and station- and satellite-based products. 20CRv3 is also able to capture trends in tropospheric-layer temperatures that correlate well with independent products in the twentieth century, placing recent trends in a longer historical context.
71 citations
South Australian Museum1, University of New South Wales2, University of Waikato3, Landcare Research4, University of Auckland5, National Institute of Water and Atmospheric Research6, University of Sheffield7, Brown University8, Zürcher Fachhochschule9, Saint Petersburg State University10, ETH Zurich11, Swiss Federal Laboratories for Materials Science and Technology12, Lund University13, Alfred Wegener Institute for Polar and Marine Research14, University of Wollongong15, American Museum of Natural History16, Keele University17, Woods Hole Oceanographic Institution18, Southern University of Science and Technology19, University of Oxford20, National University of Cordoba21, University of Adelaide22, Australian National University23, University of Jena24
TL;DR: This article used ancient New Zealand kauri trees (Agathis australis) to develop a detailed record of atmospheric radiocarbon levels across the Laschamps Excursion, finding that geomagnetic field minima ~42 ka, in combination with Grand Solar Minima, caused substantial changes in atmospheric ozone concentration and circulation, driving synchronous global climate shifts that caused major environmental changes, extinction events, and transformations in the archaeological record.
Abstract: Geological archives record multiple reversals of Earth's magnetic poles, but the global impacts of these events, if any, remain unclear. Uncertain radiocarbon calibration has limited investigation of the potential effects of the last major magnetic inversion, known as the Laschamps Excursion [41 to 42 thousand years ago (ka)]. We use ancient New Zealand kauri trees (Agathis australis) to develop a detailed record of atmospheric radiocarbon levels across the Laschamps Excursion. We precisely characterize the geomagnetic reversal and perform global chemistry-climate modeling and detailed radiocarbon dating of paleoenvironmental records to investigate impacts. We find that geomagnetic field minima ~42 ka, in combination with Grand Solar Minima, caused substantial changes in atmospheric ozone concentration and circulation, driving synchronous global climate shifts that caused major environmental changes, extinction events, and transformations in the archaeological record.
47 citations
TL;DR: In this article, the authors used Landsat 8 OLI satellite imagery from February and March 2016 for delineating clean glaciers using a semi-automatic band ratio method and debris-covered glaciers using maximum likelihood classification.
Abstract: The only complete inventory of New Zealand glaciers was based on aerial photography starting in 1978. While there have been partial updates using 2002 and 2009 satellite data, most glaciers are still represented by the 1978 outlines in contemporary global glacier databases. The objective of this project is to establish an updated glacier inventory for New Zealand. We have used Landsat 8 OLI satellite imagery from February and March 2016 for delineating clean glaciers using a semi-automatic band ratio method and debris-covered glaciers using a maximum likelihood classification. The outlines have been checked against Sentinel-2 MSI data, which have a higher resolution. Manual post processing was necessary due to misclassifications (e.g. lakes, clouds), mapping in shadowed areas, and combining the clean and debris-covered parts into single glaciers. New Zealand glaciers cover an area of 794 ± 34 km2 in 2016 with a debris-covered area of 10%. Of the 2918 glaciers, seven glaciers are >10 km2 while 71% is 40%. Only 15 glaciers are located on the North Island. For a selection of glaciers, we were able to calculate the area reduction between the 1978 and 2016 inventories.
19 citations
TL;DR: In this article, the authors constrain the chronology of a Cook Islands stalagmite using synchrotron µXRF two-dimensional mapping of Sr concentrations coupled with growth laminae optical imaging constrained by in situ monitoring.
Abstract: Tropical Pacific stalagmites are commonly affected by dating uncertainties because of their low U concentration and/or elevated initial 230Th content. This poses problems in establishing reliable trends and periodicities for droughts and pluvial episodes in a region vulnerable to climate change. Here we constrain the chronology of a Cook Islands stalagmite using synchrotron µXRF two-dimensional mapping of Sr concentrations coupled with growth laminae optical imaging constrained by in situ monitoring. Unidimensional LA-ICP-MS-generated Mg, Sr, Ba and Na variability series were anchored to the 2D Sr and optical maps. The annual hydrological significance of Mg, Sr, Ba and Na was tested by principal component analysis, which revealed that Mg and Na are related to dry-season, wind-transported marine aerosols, similar to the host-rock derived Sr and Ba signatures. Trace element annual banding was then used to generate a calendar-year master chronology with a dating uncertainty maximum of ± 15 years over 336 years. Our approach demonstrates that accurate chronologies and coupled hydroclimate proxies can be obtained from speleothems formed in tropical settings where low seasonality and problematic U-Th dating would discourage the use of high-resolution climate proxies datasets.
15 citations
TL;DR: In this paper, the authors present a new cosmogenic 10Be chronology of glacier length changes at Dart Glacier in the Southern Alps, New Zealand and suggest that rising greenhouse gas concentrations after 7 ka caused regional-scale glacier retreat and appear to be the dominant driver of multi-millennial summer temperature trends in the southern mid-latitudes during the present interglacial.
6 citations
01 May 2021
3 citations
TL;DR: In this article, a set of descriptors applied to weather regimes, that allow for a detailed monitoring of the location and intensity of their atmospheric centers of action (e.g. troughs and ridges) and the gradients between them, when applicable.
Abstract: This paper introduces a set of descriptors applied to weather regimes, that allow for a detailed monitoring of the location and intensity of their atmospheric centers of action (e.g. troughs and ridges) and the gradients between them, when applicable. Descriptors are designed to document the effect of climate variability and change in modulating the character of daily weather regimes, rather than merely their occurrence statistics.As a case study, the methodology is applied to Aotearoa New Zealand (ANZ), using ERA5 ensemble reanalysis data for the period 1979-2019. Here, we analyze teleconnections between the regimes and their descriptors, and large-scale climate variability. Results show a significant modulation of centers of action by the phase of the Southern Annular Mode, with a strong relationship identified with the latitude of atmospheric ridges. Significant associations with El Niño Southern Oscillation are also identified. Modes of large-scale variability have a stronger influence on the regimes’ intrinsic features than their occurrence. This demonstrates the usefulness of such descriptors, which help understand the relationship between mid-latitude transient perturbations and large-scale modes of climate variability.In future research, this methodological framework will be applied to analyze (i) low-frequency changes in weather regimes under climate change, in line with the southward shift of storm tracks, and (ii) regional-scale effects on the climate of ANZ, resulting from interaction with its topography.
3 citations
TL;DR: In this article, the authors present a set of floating tree ring radiocarbon chronologies that are wiggle-matched to other palaeo records (particularly to Hulu Cave speleothems) to provide detailed structure to the MIS3 portion of extant calibration curves.
2 citations
South Australian Museum1, University of New South Wales2, University of Waikato3, Landcare Research4, University of Auckland5, National Institute of Water and Atmospheric Research6, University of Sheffield7, Brown University8, Zürcher Fachhochschule9, Saint Petersburg State University10, ETH Zurich11, Swiss Federal Laboratories for Materials Science and Technology12, Lund University13, Alfred Wegener Institute for Polar and Marine Research14, University of Wollongong15, American Museum of Natural History16, Keele University17, Woods Hole Oceanographic Institution18, Southern University of Science and Technology19, University of Oxford20, University of Adelaide21, University of Jena22
TL;DR: In this paper, the impacts of the Laschamps Geomagnetic Excursion 42,000 years ago have provoked considerable scientific and public interest, particularly in the Adams Event associated with the initial transition of the magnetic poles.
Abstract: Our paper about the impacts of the Laschamps Geomagnetic Excursion 42,000 years ago has provoked considerable scientific and public interest, particularly in the so-called Adams Event associated with the initial transition of the magnetic poles. Although we welcome the opportunity to discuss our new ideas, Hawks' assertions of misrepresentation are especially disappointing given his limited examination of the material.