scholarly journals Millennial-to-centennial patterns and trends in the hydroclimate of North America over the past 2000 years

2017 ◽  
Author(s):  
Bryan N. Shuman ◽  
Cody Routson ◽  
Nicholas McKay ◽  
Sherilyn Fritz ◽  
Darrell Kaufman ◽  
...  
Keyword(s):  
Pacific Northwest ◽  
Ice Age ◽  
The Arctic ◽  
Medieval Period ◽  
The Past ◽  
Past 2000 Years ◽  
Annual Range ◽  
The Common ◽  
Common Era ◽  
Millennial Scale

Abstract. A synthesis of 93 hydrologic records from across North and Central America, and adjacent tropical and Arctic islands, reveals centennial to millennial trends in the regional hydroclimates of the Common Era (CE; past 2000 years). The hydrological records derive from materials stored in lakes, bogs, caves, and ice from extant glaciers, which have the continuity through time to preserve low-frequency (> 100 year) climate signals that may not be well represented by other shorter-lived archives, such as tree-ring chronologies. The most common pattern, represented in 46 (49 %) of the records, indicates that the centuries before 1000 CE were drier than the centuries since that time. Principal components analysis indicates that millennial-scale trends represent the dominant pattern of variance in the southwest and northeast U.S., the mid-continent, Pacific Northwest, the Arctic, and the tropics, although not all records within a region show the same direction of change. The Pacific Northwest, Greenland, and the southernmost tier of the tropical sites tended to dry toward present, as many other areas became wetter than before. Twenty-two records (24 %) indicate that the Medieval period (800–1300 CE) was drier than the Little Ice Age (1400–1900 CE), but in many cases the difference was part of the longer millennial-scale trend, and, in 25 records (27 %), the Medieval period represented a pluvial (wet) phase. Where quantitative records permitted a comparison, we found that centennial-scale fluctuations over the Common Era represented changes of 3–7 % of the modern inter-annual range of variability in precipitation, but the accumulation of these long-term trends over the entirety of the Holocene caused recent centuries to be significantly wetter, on average, than most of the past 11 000 years.

scholarly journals Placing the Common Era in a Holocene context: millennial to centennial patterns and trends in the hydroclimate of North America over the past 2000 years

2018 ◽  
Vol 14 (5) ◽  
pp. 665-686 ◽  
Author(s):  
Bryan N. Shuman ◽  
Cody Routson ◽  
Nicholas McKay ◽  
Sherilyn Fritz ◽  
Darrell Kaufman ◽  
...  
Keyword(s):  
Pacific Northwest ◽  
Ice Age ◽  
Medieval Climate Anomaly ◽  
Climate Anomaly ◽  
The Holocene ◽  
The Past ◽  
Past 2000 Years ◽  
The Common ◽  
Common Era ◽  
Millennial Scale

Abstract. A synthesis of 93 hydrologic records from across North and Central America, and adjacent tropical and Arctic islands, reveals centennial to millennial trends in the regional hydroclimates of the Common Era (CE; past 2000 years). The hydrological records derive from materials stored in lakes, bogs, caves, and ice from extant glaciers, which have the continuity through time to preserve low-frequency ( > 100 year) climate signals that may extend deeper into the Holocene. The most common pattern, represented in 46 (49 %) of the records, indicates that the centuries before 1000 CE were drier than the centuries since that time. Principal component analysis indicates that millennial-scale trends represent the dominant pattern of variance in the southwestern US, northeastern US, mid-continent, Pacific Northwest, Arctic, and tropics, although not all records within a region show the same direction of change. The Pacific Northwest and the southernmost tier of the tropical sites tended to dry toward present, as many other areas became wetter than before. In 22 records (24 %), the Medieval Climate Anomaly period (800–1300 CE) was drier than the Little Ice Age (1400–1900 CE), but in many cases the difference was part of the longer millennial-scale trend, and, in 25 records (27 %), the Medieval Climate Anomaly period represented a pluvial (wet) phase. Where quantitative records permitted a comparison, we found that centennial-scale fluctuations over the Common Era represented changes of 3–7 % in the modern interannual range of variability in precipitation, but the accumulation of these long-term trends over the entirety of the Holocene caused recent centuries to be significantly wetter, on average, than most of the past 11 000 years.

scholarly journals Low-resolution Australasian palaeoclimate records of the last 2000 years

2017 ◽  
Author(s):  
Bronwyn C. Dixon ◽  
Jonathan J. Tyler ◽  
Andrew M. Lorrey ◽  
Ian D. Goodwin ◽  
Joëlle Gergis ◽  
...  
Keyword(s):  
Climate Variability ◽  
A Priori ◽  
High Quality ◽  
Bayesian Techniques ◽  
The Past ◽  
Past 2000 Years ◽  
Dating Methods ◽  
The Common ◽  
Common Era ◽  
Australasian Region

Abstract. Non-annually resolved palaeoclimate records in the Australasian region were compiled to facilitate investigations of decadal to centennial climate variability over the past 2000 years. A total of 661 lake/wetland, geomorphic, marine, and speleothem records were identified and then assessed against a set of a priori criteria based on temporal resolution, record length, dating methods, and confidence of the proxy-climate relationship over the Common Era. A high quality subset of 22 records across Australasia met the criteria and they are endorsed for subsequent analyses. New chronologies based on progressive Bayesian techniques were constructed for the high quality records to ensure a consistent approach to age modelling and quantification of age uncertainties. Chronological uncertainty was the primary reason why records did not meet the selection criteria. Despite present limitations, existing proxies and reconstruction techniques that successfully capture climate variability in the region show potential to address spatial gaps and expand the range of climate variables covering the last 2000 years from the Australasian region.

Millennial-scale increase in winter precipitation in the southern Rocky Mountains during the Common Era

2020 ◽  
Vol 94 ◽  
pp. 1-13 ◽  
Author(s):  
Meredith C. Parish ◽  
W. John Calder ◽  
Bryan N. Shuman
Keyword(s):  
Large Change ◽  
High Elevation ◽  
Winter Precipitation ◽  
Ice Age ◽  
Annual Precipitation ◽  
Fossil Pollen ◽  
The Past ◽  
Tree Ring Data ◽  
The Common ◽  
Common Era

AbstractWe employed the modern analog technique to quantitatively reconstruct temperature and precipitation over the past 2500 yr based on fossil pollen records from six high-elevation lakes in northern Colorado. Reconstructed annual temperatures for the study area did not deviate significantly from modern over the past 2500 yr despite hemispheric expressions of Medieval Climate Anomaly warmth and Little Ice Age cooling. Annual precipitation, however, shifted from lower than modern rates from 2500 to 1000 cal yr BP to higher than modern rates after 1000 cal yr BP, a greater than 100 mm increase in precipitation. Winter precipitation accounts for the majority of the change in annual precipitation, while summer precipitation rates did not change significantly over the past 2500 yr. The large change in winter precipitation rates from the first to second millennium of the Common Era is inferred from a shift in fossil pollen assemblages dominated by subalpine conifers, which have southern sites as modern analogs, to assemblages representing open subalpine vegetation with abundant Artemisia spp. (sagebrush), which have more northern modern analogs. The change helps to explain regional increases in lake levels and shifts in some isotopic and tree-ring data sets, highlighting the risk of large reductions in snowpack and water supplies in the Intermountain West.

Advancing community-led research into the climate of the Common Era

2021 ◽  
Author(s):  
Sarah S. Eggleston ◽  
Steven Phipps ◽  
Oliver Bothe ◽  
Helen V. McGregor ◽  
Belen Martrat ◽  
...  
Keyword(s):  
Climate Science ◽  
Global Changes ◽  
Present Climate ◽  
The Third ◽  
The Past ◽  
Third Phase ◽  
The Common ◽  
Common Era ◽  
Scientific Questions ◽  
New Phase

<p>The past two thousand years is a key interval for climate science. This period encompasses both the era of human-induced global warming and a much longer interval when changes in Earth’s climate were governed principally by natural drivers and unforced variability. Since 2009, the Past Global Changes (PAGES) 2k Network has brought together hundreds of scientists from around the world to reconstruct and understand the climate of the Common Era using open and collaborative approaches to palaeoclimate science, including virtual meetings. The third phase of the network will end in December 2021. Here we highlight some key outputs of PAGES 2k and present the major themes and scientific questions emerging from recent surveys of the community. We explore how these might boost a new phase of PAGES 2k or a successor project(s). This year we will further reach out to the community through Town Hall consultations, vEGU and other meetings, and a PAGES 2k global webinar series. The aim of these activities is to foster development of post-2021 community-led PAGES initiatives that connect past and present climate.</p>

scholarly journals Episodic Neoglacial expansion and rapid 20th century retreat of a small ice cap on Baffin Island, Arctic Canada, and modeled temperature change

2017 ◽  
Vol 13 (11) ◽  
pp. 1527-1537 ◽  
Author(s):  
Simon L. Pendleton ◽  
Gifford H. Miller ◽  
Robert A. Anderson ◽  
Sarah E. Crump ◽  
Yafang Zhong ◽  
...  
Keyword(s):  
Temperature Change ◽  
Climate Model ◽  
Ice Age ◽  
The Arctic ◽  
Baffin Island ◽  
Radiocarbon Dates ◽  
The Past ◽  
Ice Cap ◽  
Climate Model Simulations ◽  
Glacier Advance

Abstract. Records of Neoglacial glacier activity in the Arctic constructed from moraines are often incomplete due to a preservation bias toward the most extensive advance, often the Little Ice Age. Recent warming in the Arctic has caused extensive retreat of glaciers over the past several decades, exposing preserved landscapes complete with in situ tundra plants previously entombed by ice. The radiocarbon ages of these plants define the timing of snowline depression and glacier advance across the site, in response to local summer cooling. Erosion rapidly removes most dead plants that have been recently exposed by ice retreat, but where erosive processes are unusually weak, dead plants may remain preserved on the landscape for decades. In such settings, a transect of plant radiocarbon ages can be used to construct a near-continuous chronology of past ice margin advance. Here we present radiocarbon dates from the first such transect on Baffin Island, which directly dates the advance of a small ice cap over the past two millennia. The nature of ice expansion between 20 BCE and ∼ 1000 CE is still uncertain, but episodic advances at ∼ 1000 CE, ∼ 1200, and  ∼ 1500 led to the maximum Neoglacial dimensions ~ 1900 CE. We employ a two-dimensional numerical glacier model calibrated using the plant radiocarbon ages ice margin chronology to assess the sensitivity of the ice cap to temperature change. Model experiments show that at least ∼ 0.44 °C of cooling over the past 2 kyr is required for the ice cap to reach its 1900 CE margin, and that the period from ∼ 1000 to 1900 CE must have been at least 0.25° C cooler than the previous millennium, results that agree with regional temperature reconstructions and climate model simulations. However, significant warming since 1900 CE is required to explain retreat to its present position, and, at the same rate of warming, the ice cap will disappear before 2100 CE.

The Common fossils of the British Rocks

The Geologist ◽  
1858 ◽  
Vol 1 (6) ◽  
pp. 238-241
Author(s):  
S. J. Mackie
Keyword(s):  
Sedimentary Rocks ◽  
The Arctic ◽  
Rock Masses ◽  
Scottish Highlands ◽  
The Past ◽  
Arctic Regions ◽  
The World ◽  
The Subject ◽  
The Common ◽  
Birth Time

A Man would see but little of the reality of the world if he shut himself up in his house, and only gazed out from the same window; he would learn little more if he contented himself with alternately gazing upon the scenes passing around him, from the windows of every storey. So a geologist, in limiting himself to the study of the rock-masses of a circumscribed area, would never, by the utmost perseverance, in going continually over the same ground, attain to a perfect understanding of the subject of his study. He must go abroad, either in his own person or equivalently, by making himself acquainted with the travels and labours of others. Our knowledge of the ancient conditions and relations of the oldest rock-masses would not be complete if we limited our investigations to those isolated patches in our own country, which, however important, are still only a part of that great whole, more important traces of which are to be met in regions far away. Thus those very old—indeed, primitive sedimentary rocks, represented in the British Isles in a fragmentary manner, as by the younger or bedded gneiss of the Scottish Highlands, assume in Canada and the Arctic regions proportions of great extent, and consequently, of far greater value. Far back in the obscurity of the past, as must be placed the birth-time of these primitive land-masses, we seem, in our first investigations, plunged in interminable ignorance, like the explorers of some vast subterranean cave in impenetrable darkness.

Climate of the Little Ice Age and the past 2000 years in northeast Iceland inferred from chironomids and other lake sediment proxies

2008 ◽  
Vol 41 (1) ◽  
pp. 7-24 ◽  
Author(s):  
Yarrow Axford ◽  
Áslaug Geirsdóttir ◽  
Gifford H. Miller ◽  
Peter G. Langdon
Keyword(s):  
Lake Sediment ◽  
Little Ice Age ◽  
Ice Age ◽  
The Past ◽  
Past 2000 Years

A 2000-yr-long multi-proxy lacustrine record from eastern Baffin Island, Arctic Canada reveals first millennium AD cold period

2011 ◽  
Vol 75 (3) ◽  
pp. 491-500 ◽  
Author(s):  
Elizabeth K. Thomas ◽  
Jason P. Briner ◽  
Yarrow Axford ◽  
Donna R. Francis ◽  
Gifford H. Miller ◽  
...  
Keyword(s):  
Organic Matter ◽  
Cold Climate ◽  
Trophic Levels ◽  
Ice Age ◽  
The Arctic ◽  
Time Interval ◽  
Baffin Island ◽  
Arctic Canada ◽  
The Past ◽  
First Millennium

AbstractWe generate a multi-proxy sub-centennial-scale reconstruction of environmental change during the past two millennia from Itilliq Lake, Baffin Island, Arctic Canada. Our reconstruction arises from a finely subsectioned 210Pb- and 14C-dated surface sediment core and includes measures of organic matter (e.g., chlorophyll a; carbon–nitrogen ratio) and insect (Diptera: Chironomidae) assemblages. Within the past millennium, the least productive, and by inference coldest, conditions occurred ca. AD 1700–1850, late in the Little Ice Age. The 2000-yr sediment record also reveals an episode of reduced organic matter deposition during the 6th–7th century AD; combined with the few other records comparable in resolution that span this time interval from Baffin Island, we suggest that this cold episode was experienced regionally. A comparable cold climatic episode occurred in Alaska and western Canada at this time, suggesting that the first millennium AD cold climate anomaly may have occurred throughout the Arctic. Dramatic increases in aquatic biological productivity at multiple trophic levels are indicated by increased chlorophyll a concentrations since AD 1800 and chironomid concentrations since AD 1900, both of which have risen to levels unprecedented over the past 2000 yr.

scholarly journals Early Holocene cold snaps and their expression in the moraine record of the Eastern European Alps

2021 ◽  
Author(s):  
Sandra M. Braumann ◽  
Joerg M. Schaefer ◽  
Stephanie M. Neuhuber ◽  
Christopher Lüthgens ◽  
Alan J. Hidy ◽  
...  
Keyword(s):  
Climate Change ◽  
Arctic Region ◽  
Climate System ◽  
Early Holocene ◽  
Ice Age ◽  
The Arctic ◽  
European Alps ◽  
Eastern European ◽  
Exposure Dating ◽  
The Past

Abstract. Glaciers preserve climate variations in their geological and geomorphological records, which makes them prime candidates for climate reconstructions. Investigating the glacier-climate system over the past millennia is particularly relevant because, first, the amplitude and frequency of natural climate variability during the Holocene provides the climatic context against which modern, human-induced climate change must be assessed. Second, the transition from the last glacial to the current interglacial promises important insights into the climate system during warming, which is of particular interest with respect to ongoing climate change. Evidence of stable ice margin positions that record cooling during the past 12 ka are preserved in two glaciated valleys of the Silvretta Massif in the Eastern European Alps, the Jamtal (JAM) and the Laraintal (LAR). We mapped and dated moraines in these catchments including historical ridges using Beryllium-10 Surface Exposure Dating (10Be SED) techniques, and correlate resulting moraine formation intervals with climate proxy records to evaluate the spatial and temporal scale of these cold phases. The new geochronologies indicate two moraine formation intervals (MFI) during the Early Holocene (EH): 10.8 ± 0.7 ka (n = 9) and 11.2 ± 0.8 ka (n = 12). Boulder ages along historical moraines (n = 6) imply at least two glacier advances during the Little Ice Age (LIA; c. 1250–1850 CE), around 1300 CE and in the second half of the 18th century. An earlier advance to the same position may have occurred around 500 CE. The Jamtal and Laraintal moraine chronologies provide evidence that millennial scale EH warming was superimposed by centennial scale cooling. The timing of EH moraine formation is contemporaneous with brief temperature drops identified in local and regional paleoproxy records, most prominently with the Preboreal Oscillation (PBO), and is consistent with moraine deposition in other catchments in the European Alps, and in the Arctic region. This consistency points to cooling beyond the local scale and therefore a regional or even hemispheric climate driver. Freshwater input sourced from the Laurentide Ice Sheet (LIS), which changed circulation patterns in the North Atlantic, is a plausible explanation for EH cooling and moraine formation in the Nordic region and in Europe.

scholarly journals Higher-than-present Medieval pine (Pinus sylvestris) treeline along the Swedish Scandes

2015 ◽  
Vol 42 ◽  
pp. 1-14 ◽  
Author(s):  
Leif Kullman
Keyword(s):  
Pinus Sylvestris ◽  
Ground Surface ◽  
Ice Age ◽  
Lapse Rate ◽  
Medieval Period ◽  
Climate Change And Variability ◽  
The Past ◽  
Northern Fennoscandia ◽  
Detection And Attribution ◽  
Summer Temperatures

The upper treeline of Scots pine (Pinus sylvestris L.) is renowned as a sensitive indicator of climate change and variability. By use of megafossil tree remains, preserved exposed on the ground surface, treeline shift over the past millennium was investigated at multiple sites along the Scandes in northern Sweden. Difference in thermal level between the present and the Medieval period, about AD 1000-1200, is a central, although controversial, aspect concerning the detection and attribution of anthropogenic climate warming. Radiocarbon-dated megafossil pines revealed that the treeline was consistently positioned as much as 115 m higher during the Medieval period than today (AD 2000-2010), after a century of warming and substantial treeline upshift. Drawing on the last-mentioned figure, and a lapse rate of 0.6oC/100 m, it may be inferred that Medieval summer temperatures were about 0.7 oC warmer than much of the past 100 years. Extensive pine mortality and treeline descent after the Medieval warming peak reflect substantially depressed temperatures during the Little Ice Age. Warmer-than-present conditions during the Medieval period concur with temperature reconstructions from different parts of northern Fennoscandia, northwestern Russia and Greenland. Modern warming has not been sufficient to restore Medieval treelines. Against this background, there is little reason to view further modest warming as unnatural.

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