Spatial structure of the 8200 cal yr BP event in northern Europe

Abstract. A synthesis of well-dated high-resolution pollen records suggests a spatial structure in the 8200 cal yr BP event in northern Europe. The temperate, thermophilous tree taxa, especially Corylus, Ulmus, and Alnus, decline abruptly between 8300 and 8000 cal yr BP at most sites located south of 61° N, whereas there is no clear change in pollen values at the sites located in the North-European tree-line region. Pollen-based quantitative temperature reconstructions and several other, independent palaeoclimate proxies, such as lacustrine oxygen-isotope records, reflect the same pattern, with no detectable cooling in the sub-arctic region. The observed patterns challenges the general view of the wide-spread occurrence of the 8200 cal yr BP event in the North Atlantic region. An alternative explanation is that the cooling during the 8200 cal yr BP event took place mostly during the winter and spring, and the ecosystems in the south responded sensitively to the cooling during the onset of the growing season. In contrast, in the sub-arctic area, where the vegetation was still dormant and lakes ice-covered, the cold event is not reflected in pollen-based or lake-sediment-based records.

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Spatial structure of the 8200 cal yr BP event in Northern Europe

Climate of the Past Discussions ◽

10.5194/cpd-3-165-2007 ◽

2007 ◽

Vol 3 (1) ◽

pp. 165-195 ◽

Cited By ~ 20

Author(s):

H. Seppä ◽

H. J. B. Birks ◽

T. Giesecke ◽

D. Hammarlund ◽

T. Alenius ◽

...

Keyword(s):

Spatial Structure ◽

Arctic Region ◽

The Arctic ◽

Northern Europe ◽

General View ◽

Cold Event ◽

The North ◽

Arctic Regions ◽

Line Region ◽

Arctic Area

Abstract. A synthesis of well-dated high-resolution pollen records suggests a spatial structure in the 8200 cal yr BP event in northern Europe. The temperate, thermophilous tree taxa, especially Corylus, Ulmus, and Alnus, decline abruptly between 8300 and 8000 cal yr BP at most sites located south of 61° N, whereas there is no clear change in pollen values at the sites located in the North-European tree-line region. Pollen-based quantitative temperature reconstructions and several other, independent palaeoclimate proxies, such as lacustrine oxygen-isotope records, reflect the same pattern, with no detectable cooling in the sub-arctic region. The observed pattern would challenge the general view of the wide-spread occurrence of the 8200 cal yr BP event in the North Atlantic region. An alternative explanation is that the cooling during the 8200 cal yr BP event took place mostly during the winter and spring, and the ecosystems in the south responded sensitively to the cooling during the onset of the growing season. In contrast, in the sub-arctic area, where the vegetation was still dormant and lakes ice-covered, the cold event is not reflected in pollen-based or lake-sediment-based records. The arctic regions may therefore not always be optimal for detecting past climate changes.

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REGIONAL SECURITY DYNAMICS IN NORTHERN EUROPE (ON THE EXAMPLE OF NORWAY) IN THE LIGHT OF RECENT CHANGES

BULLETIN Series of Sociological and Political sciences ◽

10.51889/2021-1.1728-8940.14 ◽

2020 ◽

Vol 73 (1) ◽

pp. 103-111

Author(s):

D. Kalibekuly ◽

◽

Y.S. Chukubayev ◽

Keyword(s):

North Atlantic ◽

Member Country ◽

Security Policy ◽

Security System ◽

Regional Security ◽

Northern Europe ◽

The North ◽

The North Atlantic ◽

The Impact

The paper examines the dynamics of regional security in Norway as a part of Northern Europe. Being a political and geographical part of the Euro-Atlantic security system. Northern Europe, in its turn, is experiencing the impact of the confrontation between Russia and NATO. Norway's security policy analyzed from the perspective of a regional leader, as a NATO member country participating in the operations of the North Atlantic Alliance and as NATO's northern wing.

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Trends and fluctuations in the dates of ice break-up of lakes and rivers in Northern Europe: the effect of the North Atlantic Oscillation

Journal of Hydrology ◽

10.1016/s0022-1694(02)00161-0 ◽

2002 ◽

Vol 268 (1-4) ◽

pp. 100-112 ◽

Cited By ~ 48

Author(s):

JaeChan Yoo ◽

Paolo D'Odorico

Keyword(s):

North Atlantic Oscillation ◽

North Atlantic ◽

Northern Europe ◽

The North ◽

The North Atlantic ◽

Break Up ◽

The North Atlantic Oscillation

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Near-surface wind speeds in ERA5: Climatology, decadal variability and long-term trends

10.5194/egusphere-egu21-4472 ◽

2021 ◽

Author(s):

Terhi K. Laurila ◽

Victoria A. Sinclair ◽

Hilppa Gregow

Keyword(s):

Iberian Peninsula ◽

North Atlantic ◽

Decadal Variability ◽

Surface Wind ◽

Northern Europe ◽

Near Surface ◽

Wind Speeds ◽

The North ◽

The North Atlantic

The knowledge of long-term climate and variability of near-surface wind speeds is essential and widely used among meteorologists, climate scientists and in industries such as wind energy and forestry. The new high-resolution ERA5 reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF) will likely be used as a reference in future climate projections and in many wind-related applications. Hence, it is important to know what is the mean climate and variability of wind speeds in ERA5.We present the monthly 10-m wind speed climate and decadal variability in the North Atlantic and Europe during the 40-year period (1979-2018) based on ERA5. In addition, we examine temporal time series and possible trends in three locations: the central North Atlantic, Finland and Iberian Peninsula. Moreover, we investigate what are the physical reasons for the decadal changes in 10-m wind speeds.The 40-year mean and the 98th percentile wind speeds show a distinct contrast between land and sea with the strongest winds over the ocean and a seasonal variation with the strongest winds during winter time. The winds have the highest values and variabilities associated with storm tracks and local wind phenomena such as the mistral. To investigate the extremeness of the winds, we defined an extreme find factor (EWF) which is the ratio between the 98th percentile and mean wind speeds. The EWF is higher in southern Europe than in northern Europe during all months. Mostly no statistically significant linear trends of 10-m wind speeds were found in the 40-year period in the three locations and the annual and decadal variability was large.The windiest decade in northern Europe was the 1990s and in southern Europe the 1980s and 2010s. The decadal changes in 10-m wind speeds were largely explained by the position of the jet stream and storm tracks and the strength of the north-south pressure gradient over the North Atlantic. In addition, we investigated the correlation between the North Atlantic Oscillation (NAO) and the Atlantic Multi-decadal Oscillation (AMO) in the three locations. The NAO has a positive correlation in the central North Atlantic and Finland and a negative correlation in Iberian Peninsula. The AMO correlates moderately with the winds in the central North Atlantic but no correlation was found in Finland or the Iberian Peninsula. Overall, our study highlights that rather than just using long-term linear trends in wind speeds it is more informative to consider inter-annual or decadal variability.

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Investigating the impact of Lake Agassiz drainage routes on the 8.2 ka cold event with a climate model

Climate of the Past ◽

10.5194/cp-5-471-2009 ◽

2009 ◽

Vol 5 (3) ◽

pp. 471-480 ◽

Cited By ~ 8

Author(s):

Y.-X. Li ◽

H. Renssen ◽

A. P. Wiersma ◽

T. E. Törnqvist

Keyword(s):

Atlantic Ocean ◽

North Atlantic ◽

Climate Model ◽

North Atlantic Ocean ◽

Sensitivity Study ◽

Meridional Overturning Circulation ◽

Labrador Sea ◽

Cold Event ◽

The North ◽

The Impact

Abstract. The 8.2 ka event is the most prominent abrupt climate change in the Holocene and is often believed to result from catastrophic drainage of proglacial lakes Agassiz and Ojibway (LAO) that routed through the Hudson Bay and the Labrador Sea into the North Atlantic Ocean, and perturbed Atlantic meridional overturning circulation (MOC). One key assumption of this triggering mechanism is that the LAO freshwater drainage was dispersed over the Labrador Sea. Recent data, however, show no evidence of lowered δ18O values, indicative of low salinity, from the open Labrador Sea around 8.2 ka. Instead, negative δ18O anomalies are found close to the east coast of North America, extending as far south as Cape Hatteras, North Carolina, suggesting that the freshwater drainage may have been confined to a long stretch of continental shelf before fully mixing with North Atlantic Ocean water. Here we conduct a sensitivity study that examines the effects of a southerly drainage route on the 8.2 ka event with the ECBilt-CLIO-VECODE model. Hosing experiments of four routing scenarios, where freshwater was introduced to the Labrador Sea in the northerly route and to three different locations along the southerly route, were performed to investigate the routing effects on model responses. The modeling results show that a southerly drainage route is possible but generally yields reduced climatic consequences in comparison to those of a northerly route. This finding implies that more freshwater would be required for a southerly route than for a northerly route to produce the same climate anomaly. The implicated large amount of LAO drainage for a southerly routing scenario is in line with a recent geophysical modelling study of gravitational effects on sea-level change associated with the 8.2 ka event, which suggests that the volume of drainage might be larger than previously estimated.

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CMIP5 Projections of Arctic Amplification, of the North American/North Atlantic Circulation, and of Their Relationship

Journal of Climate ◽

10.1175/jcli-d-14-00589.1 ◽

2015 ◽

Vol 28 (13) ◽

pp. 5254-5271 ◽

Cited By ~ 112

Author(s):

Elizabeth A. Barnes ◽

Lorenzo M. Polvani

Keyword(s):

North Atlantic ◽

Climate Models ◽

Coupled Model ◽

Arctic Region ◽

The Arctic ◽

Cmip5 Models ◽

Arctic Amplification ◽

Arctic Warming ◽

The North ◽

Sequence Of Events

Abstract Recent studies have hypothesized that Arctic amplification, the enhanced warming of the Arctic region compared to the rest of the globe, will cause changes in midlatitude weather over the twenty-first century. This study exploits the recently completed phase 5 of the Coupled Model Intercomparison Project (CMIP5) and examines 27 state-of-the-art climate models to determine if their projected changes in the midlatitude circulation are consistent with the hypothesized impact of Arctic amplification over North America and the North Atlantic. Under the largest future greenhouse forcing (RCP8.5), it is found that every model, in every season, exhibits Arctic amplification by 2100. At the same time, the projected circulation responses are either opposite in sign to those hypothesized or too widely spread among the models to discern any robust change. However, in a few seasons and for some of the circulation metrics examined, correlations are found between the model spread in Arctic amplification and the model spread in the projected circulation changes. Therefore, while the CMIP5 models offer some evidence that future Arctic warming may be able to modulate some aspects of the midlatitude circulation response in some seasons, the analysis herein leads to the conclusion that the net circulation response in the future is unlikely to be determined solely—or even primarily—by Arctic warming according to the sequence of events recently hypothesized.

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Timing and duration of North American glacial lake discharges and the Younger Dryas climate reversal

Quaternary Research ◽

10.1016/j.yqres.2011.02.004 ◽

2011 ◽

Vol 75 (3) ◽

pp. 541-551 ◽

Cited By ~ 35

Author(s):

John A. Rayburn ◽

Thomas M. Cronin ◽

David A. Franzi ◽

Peter L.K. Knuepfer ◽

Debra A. Willard

Keyword(s):

Ocean Circulation ◽

North Atlantic ◽

North American ◽

Younger Dryas ◽

Ice Cores ◽

Cold Event ◽

Lawrence Estuary ◽

The North ◽

The North Atlantic ◽

Proglacial Lake

AbstractRadiocarbon-dated sediment cores from the Champlain Valley (northeastern USA) contain stratigraphic and micropaleontologic evidence for multiple, high-magnitude, freshwater discharges from North American proglacial lakes to the North Atlantic. Of particular interest are two large, closely spaced outflows that entered the North Atlantic Ocean via the St. Lawrence estuary about 13,200–12,900 cal yr BP, near the beginning of the Younger Dryas cold event. We estimate from varve chronology, sedimentation rates and proglacial lake volumes that the duration of the first outflow was less than 1 yr and its discharge was approximately 0.1 Sv (1 Sverdrup = 106 m3 s−1). The second outflow lasted about a century with a sustained discharge sufficient to keep the Champlain Sea relatively fresh for its duration. According to climate models, both outflows may have had sufficient discharge, duration and timing to affect meridional ocean circulation and climate. In this report we compare the proglacial lake discharge record in the Champlain and St. Lawrence valleys to paleoclimate records from Greenland Ice cores and Cariaco Basin and discuss the two-step nature of the inception of the Younger Dryas.

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Tracking Moisture Sources of Precipitation over Central Asia: A Study Based on the Water-Source-Tagging Method

Journal of Climate ◽

10.1175/jcli-d-20-0169.1 ◽

2020 ◽

Vol 33 (23) ◽

pp. 10339-10355

Author(s):

Jie Jiang ◽

Tianjun Zhou ◽

Hailong Wang ◽

Yun Qian ◽

David Noone ◽

...

Keyword(s):

Central Asia ◽

North Atlantic ◽

North Atlantic Ocean ◽

Northern Europe ◽

Moisture Sources ◽

The North ◽

Westerly Jet ◽

Drying Trend ◽

The North Atlantic ◽

Subtropical Westerly Jet

AbstractCentral Asia is a semiarid to arid region that is sensitive to hydrological changes. We use the Community Atmosphere Model, version 5 (CAM5), equipped with a water-tagging capability, to investigate the major moisture sources for climatological precipitation and its long-term trends over central Asia. Europe, the North Atlantic Ocean, and local evaporation, which explain 33.2% ± 1.5%, 23.0% ± 2.5%, and 19.4% ± 2.2% of the precipitation, respectively, are identified as the most dominant moisture sources for northern central Asia (NCA). For precipitation over southern central Asia (SCA), Europe, the North Atlantic, and local evaporation contribute 25.4% ± 2.7%, 18.0% ± 1.7%, and 14.7% ± 1.9%, respectively. In addition, the contributions of South Asia (8.6% ± 1.7%) and the Indian Ocean (9.5% ± 2.0%) are also substantial for SCA. Modulated by the seasonal meridional shift in the subtropical westerly jet, moisture originating from the low and midlatitudes is important in winter, spring, and autumn, whereas northern Europe contributes more to summer precipitation. We also explain the observed drying trends over southeastern central Asia in spring and over NCA in summer during 1956–2005. The drying trend over southeastern central Asia in spring is mainly due to the decrease in local evaporation and weakened moisture fluxes from the Arabian Peninsula and Arabian Sea associated with the warming of the western Pacific Ocean. The drying trend over NCA in summer can be attributed to a decrease in local evaporation and reduced moisture from northern Europe that is due to the southward shift of the subtropical westerly jet.

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