Search results for "Atlantic Oscillation"

Bunker Cave stalagmites: an archive for central European Holocene climate variability

2012

Holocene climate was characterised by variability on multi-centennial to multi-decadal time scales. In central Europe, these fluctuations were most pronounced during winter. Here we present a record of past winter climate variability for the last 10.8 ka based on four speleothems from Bunker Cave, western Germany. Due to its central European location, the cave site is particularly well suited to record changes in precipitation and temperature in response to changes in the North Atlantic realm. We present high-resolution records of δ<sup>18</sup>O, δ<sup>13</sup>C values and Mg/Ca ratios. Changes in the Mg/Ca ratio are attributed to past meteoric p…

Variabilité de la température entre 1951 et 2014 en Allemagne associée à l’évolution de la floraison des pommiers.

2018

Apple tree bloom onset in Germany has advanced by 2 days/decade in 1951-2014 and by 3 days/decade in 1988-2014, behaving similarly in respect to its evolution since 1951 and its sensitivity to temperature to other species’ phenological spring phases. The evolution however was not linear; by conducting a split moving-window dissimilarity analysis (SMWDA) we were able to detect the “break-period” 1987-1989 which coincides with a breakpoint that has been identified in the phases of the North Atlantic Oscillation (NAO). We observed distinct spatial patterns with apple bloom advancing from southwest to northeast and, most interestingly, a longitudinal gradient in the trend of apple bloom onset r…

Late Holocene precipitation and temperature changes in Northern Europe linked with North Atlantic forcing

2015

2020

Abstract. The vertical distribution and seasonal variation of water vapour volume mixing ratio (H2O VMR), of relative humidity with respect to ice (RHice) and particularly of regions with ice-supersaturated air masses (ISSRs) in the extratropical upper troposphere and lowermost stratosphere are investigated at northern mid-latitudes over the eastern North American, North Atlantic and European regions for the period 1995 to 2010. Observation data originate from regular and continuous long-term measurements on board instrumented passenger aircraft in the framework of the European research programme MOZAIC (1994–2010), which continues as the European research infrastructure IAGOS (from 2011). …

Planktic foraminiferal changes in the western Mediterranean Anthropocene

2021

The increase in anthropogenic induced warming over the last two centuries is impacting marine environment. Planktic foraminifera are a globally distributed calcifying marine zooplankton responding sensitively to changes in sea surface temperatures and interacting with the food web structure. Here, we study two high resolution multicore records from two western Mediterranean Sea regions (Alboran and Balearic basins), areas highly affected by both natural climate change and anthropogenic warming. Cores cover the time interval from the Medieval Climate Anomaly to present. Reconstructed sea surface temperatures are in good agreement with other results, tracing temperature changes through the Co…

North-Atlantic Oscillation and regional-scale sea-surge variability in Gulf of Lions during the 20th century

2010

Article soumis; International audience; Sea-surge variations recorded at three tide-gauge stations (Grau-de-la-Dent, Sète, and Port-Vendres) around the Gulf of Lions (Northwest Mediterranean Sea) are mostly locally forced by onshore winds blowing from 90° to 180° related to an atmospheric depression usually centered between the Bay of Biscay and the British Island, which is more prevalent during the negative phase of the North-Atlantic Oscillation (NAO). During the second half of the 20th century, the long-term increase of sea-surge height at Grau-de-la-Dent finds no counterpart in the positive deviation of the NAO. The relationship between the monthly frequency of sea surges > 20 cm at Gra…

Influence of climate change on phenological phases in Latvia and Lithuania

2009

To investigate the impact of recent climatic changes on plant development, this study used phenological data of the volunteer networks in Latvia and Lithuania from the 1971-2000 period. The phenological calendar method was applied. Phenological seasons were described using data on 6 phenological phases at 10 stations. The growing season was described using birch Betula pendula as an example. Correlation analysis, linear regression and non-parametric Mann-Kendall trend tests were applied to establish the relationship between phenological phases and meteorological factors (temperature, precipitation) and the North Atlantic Oscillation (NAO). The results indicate a statisti- cally significant …

Recent changes in measured wind in the NE Atlantic and variability of correlation with NAO

2010

The paper deals with wind measurements, recorded since the 1950s, at twelve meteorological stations along a transect near the westernmost European border, between 64° and 44° N. Extreme wind speed tends to decrease sharply near the northern boundary (at Reykjavick), near the middle of the study area (at Shannon and Valentia) and near the southern boundary (at Brest and Cap Ferret), to increase at Thorshavn, with less significant trends at the other stations. Average wind speeds confirm the above tendencies, with an additional increasing speed at Lerwick, Kirkwall, Malin Head, Belle-Ile and Cap Ferret. To compare changes in wind activity, the data have been subdivided into three periods: unt…

Interannual variability of Greenland winter precipitation sources: Lagrangian moisture diagnostic and North Atlantic Oscillation influence

2008

[1] We present a new Lagrangian diagnostic for identifying the sources of water vapor for precipitation. Unlike previous studies, the method allows for a quantitative demarcation of evaporative moisture sources. This is achieved by taking into account the temporal sequence of evaporation into and precipitation from an air parcel during transport, as well as information on its proximity to the boundary layer. The moisture source region diagnostic was applied to trace the origin of water vapor for winter precipitation over the Greenland ice sheet for 30 selected months with pronounced positive, negative, and neutral North Atlantic Oscillation (NAO) index, using the European Centre for Medium-…

Interannual variability of Greenland winter precipitation sources: 2. Effects of North Atlantic Oscillation variability on stable isotopes in precipi…

2008

[1] A new Lagrangian moisture source diagnostic is applied to identify the atmospheric conditions relevant for the fractionation of stable water isotopes during evaporation over the ocean and subsequent transport to Greenland. Northern Hemisphere winter months with positive and negative North Atlantic Oscillation (NAO) index are studied on the basis of ERA-40 reanalysis data. Diagnosed moisture transport conditions are supplied to a Rayleigh-type isotope fractionation model to derive estimates for the isotopic composition of stable isotopes in winter precipitation on the Greenland plateau for the two NAO phases. Because of changes in atmospheric circulation, moisture source locations for pr…