Sökresultat

Vegetation dynamics during the earliest part of the Holocene (11,250-10,250 cal yr BP) have been reconstructed from a lacustrine sequence on Sandoy, the Faroe Islands, using detailed plant macrofossil and pollen evidence. The plant macrofossils suggest the initial vegetation was sparse herb and shrub tundra, with Salix herbacea and open-ground species, followed by the development of a denser and m

The Amazon is one of the few continental regions where atmospheric aerosol particles and their effects on climate are not dominated by anthropogenic sources. During the wet season, the ambient conditions approach those of the pristine pre-industrial era. We show that the fine submicrometer particles accounting for most cloud condensation nuclei are predominantly composed of secondary organic mater

Isla de los Estados is a mountainous island southeast of Tierra del Fuego, in southernmost South America. Its central and eastern parts have an alpine topography, transected by U-shaped valleys, small, partly over-deepened fjords, and a multitude of abandoned cirques, all associated with extensive former local glaciations. Traces of glacial erosion generally reach 400-450 m a.s.l., and above that

Pollen accumulation rates (PARs) provide a potential proxy for quantitative tree volume (m3 ha-1) reconstruction with reliable absolute pollen productivity estimates (APPEs). We obtained APPEs for pine, spruce and birch at their range limits in northern Finland under two temperature periods (warm and cold) based on long-term pollen trap and tree volume records within a 14-km radius of each trap. A

During the last glacial period, proxy records throughout the Northern Hemisphere document a succession of rapid millennial-scale warming events, called Dansgaard-Oeschger (DO) events. A range of different mechanisms has been proposed that can produce similar warming in model experiments; however, the progression and ultimate trigger of the events are still unknown. Because of their fast nature, th

In recent years, cognitive robots have started to find their way into manufacturing halls. However, the full potential of these robots can only be exploited through (a) an integration of the robots with the Manufacturing Execution System (MES), (b) a new and simpler way of programming based on robot skills, automated task planning, and knowledge modeling, and (c) enabling the robots to function in

Characterizing aerosol chemical composition in response to meteorological changes and atmospheric chemistry is important to gain insights into new particle formation mechanisms. A BAECC (Biogenic Aerosols - Effects on Clouds and Climate) campaign was conducted during the spring 2014 at the SMEAR II station (Station for Measuring Forest Ecosystem-Aerosol Relations) in Finland. The particles were ch

Sensitivity tests were conducted using a state-of-the-art aerosol–cloud to investigate the key microphysical and dynamical mechanisms by which solid aerosols affect glaciated clouds. The tests involved simulations of two contrasting cases of deep convection—a tropical maritime case and a midlatitude continental case, in which solid aerosol concentrations were increased from their pre-industrial (1

We present a study on the stratospheric aerosol load during 2006-2015, discuss the influence from volcanism and other sources, and reconstruct an aerosol optical depth (AOD) data set in a resolution of 1° latitudinally and 8 days timewise. The purpose is to include the "entire" stratosphere, from the tropopause to the almost particle-free altitudes of the midstratosphere. A dynamic tropopause of 1

Numerical weather prediction models are increasing in resolution and becoming capable of explicitly representing individual convective storms, but we do not yet know if it is the improved resolution that is leading to better forecasts.

The Younger Dryas (YD) cold reversal interrupts the warming climate of the deglaciation with global climatic impacts. The sudden cooling is typically linked to an abrupt slowdown of the Atlantic Meridional Overturning Circulation (AMOC) in response to meltwater discharges from ice sheets. However, inconsistencies regarding the YD-response of European summer temperatures have cast doubt whether the

The Holocene Series/Epoch is the most recent series/epoch in the geological timescale, spanning the interval from 11,700 yr to the present day. Together with the subadjacent Pleistocene, it comprises the Quaternary System/Period. The Holocene record contains diverse geomorphological, biological, climatological and archaeological evidence, within sequences that are often continuous and extremely w

The second phase of the Fifth International Ice Nucleation Workshop (FIN-02) involved the gathering of a large number of researchers at the Karlsruhe Institute of Technology's Aerosol Interactions and Dynamics of the Atmosphere (AIDA) facility to promote characterization and understanding of ice nucleation measurements made by a variety of methods used worldwide. Compared to the previous workshop

During the transition from the last glacial into the Holocene interglacial, the atmospheric circulation in the North Atlantic area changed from a glacial mode, influenced by the presence of large ice sheets, into a system more similar to that of the present day. This change had implications for wind, temperature and precipitation patterns that can be traced in geological archives. Here, we focus o

This article summarizes the processes that are responsible for cosmogenic radionuclide variations in ice cores and the results that can be inferred from these records. The article starts with the production in the atmosphere caused by the influx of galactic cosmic ray particles and its modulation by the solar and geomagnetic fields. Subsequently, the geochemical behavior of cosmogenic radionuclide

Timescale uncertainties between paleoclimate reconstructions often inhibit studying the exact timing, spatial expression and driving mechanisms of climate variations. Detecting and aligning the globally common cosmogenic radionuclide production signal via a curve fitting method provides a tool for the quasi-continuous synchronization of paleoclimate archives. In this study, we apply this approach

The volcanic fingerprint on the winter North Atlantic atmospheric circulation and climate is analyzed in six ensemble runs of ECHAM5/MPI-OM covering 800–2000 CE, both for equatorial and Northern Hemisphere (NH) eruptions. Large volcanic eruptions influence climate on both annual and decadal time scales due to dynamic interactions of different climate components in the Earth's system. It is well kn

Spatial correlation across an antenna array is known to be detrimental to the terminal signal-to- interference-plus-noise-ratio (SINR) and system spectral efficiency. For a downlink multiuser multiple-input multiple-output system (MU-MIMO), we show that the widely used, yet overly simplified, correlation models which generate fixed correlation patterns for all terminals tend to underestimate the s

During the last glacial period Northern Hemisphere climate was characterized by extreme and abrupt climate changes, so-called Dansgaard-Oeschger (DO) events. Most clearly observed as temperature changes in Greenland ice-core records, their climatic imprint was geographically widespread. However, the temporal relation between DO events in Greenland and other regions is uncertain due to the chronolo