Holocene humidity fluctuations in Sweden inferred from dendrochronology and peat stratigraphy

Tree-ring and peat stratigraphy data were examined back to 5000 BC in order to identify and compare humidity changes in Fennoscandia. The temporal variation in distribution of Scots pine ( Pinus sylvestris L.) was used as a measure of past lake-level fluctuations in central Sweden. The chronology, which spans 2893 BC–AD 1998 with minor gaps in AD 887–907 and 1633–1650 BC and with additional floating chronologies back to 4868 BC, was cross-dated and fixed to an absolute timescale using a chronology from Torneträsk, northern Sweden. The peat stratigraphy from the Stömyren peat bog, south-central Sweden, was transformed into humification indices to evaluate humidity changes during the past 8000 years. The peat chronology is established by four tephra datings and eight ¹⁴C datings. Synchronous periods of drier conditions, interpreted from regeneration and the mortality pattern of pine, tree-ring chronology and peat humification, were recognized at c. 4900–4800 BC, 2400–2200 BC, 2100–1800 BC, 1500–1100 BC, AD 50–200, AD 400–600 and AD 1350–1500. Possible wetter periods were encountered at 3600–3400 BC, 3200–2900 BC, 2200–2100 BC, 1700–1500 BC, 1100–900 BC, 100 BC-AD 50, AD 200–400, AD 750–900 and AD 1550–1700. The wet and dry periods revealed by the tree rings and peat stratigraphy data indicate considerable humidity changes in the Holocene.     

Erosional furrows on continental shelf edge,Mississippi delta region

Erosional furrows are recognized on the seafloor off the Mississippi Delta, trending downslope over the shelf edge. They occur in water depths of 150 to 380 m seaward of presently active mudslides on the delta slope. The furrows cross an area of former mudslide deposition and part of the outer shelf. Their origin is likely to be related to cross-shelf secondary helical flows, although delta-front mass movement could cause similar erosional gouging.     

BLOCK ADJUSTMENT BY THE DIRECTION METHOD

The author explains a simple semi-graphic method of block adjustment of aerial triangulation from transformed strip co-ordinates.     

A preliminary estimate of changing calcrete carbon storage on land since the Last Glacial Maximum

The glacial-to-interglacial shift in land carbon storage is important in understanding the global carbon cycle and history of the climate system. While organic carbon storage on land appears to have been much less than present during the cold, dry glacial maximum, calcrete (soil carbonate) carbon storage would have been greater. Here we attempt a global estimation of this change; we use published figures for present soil carbonate by biome to estimate changing global soil carbonate storage, on the basis of reconstruction of vegetation areas for four timeslices since the Last Glacial Maximum. It appears that there would most likely have been around a 30–45% decrease in calcrete carbon on land accompanying the transition between glacial and interglacial conditions. This represents a change of about 500–400 GtC (outer error limits are estimated at 750–200 GtC) . In order to be weathered into dissolved bicarbonate, this would take up an additional 500–400 GtC (750–200 GtC) in CO₂ from ocean/atmosphere sources. An equivalent amount to the carbonate leaving the caliche reservoir on land may have accumulated in coral reefs and other calcareous marine sediments during the Holocene, liberating an equimolar quantity of CO₂ back into the ocean-atmosphere system as the bicarbonate ion breaks up.     

Magnetic storm acceleration of radiation belt electrons observed by the Scintillating Fibre Detector (SFD) onboard EQUATOR-S

On the basis of the currents induced by electron fluxes in the Scintillating Fibre Detector (SFD) onboard the EQUATOR-S satellite launched on 2 December 1997, an in-situ acceleration of radiation belt electrons is found to possibly contribute to the increase of the flux of electrons with energies greater than 400 keV. The data acquired between 16 December 1997 and 30 April 1998 on the 500–67300 km, 4° inclination EQUATOR-S orbit show that the increase of the energetic electron flux corresponds to the enhanced geomagnetic activity measured through the Dst index.     

Discrepancies in earthquake location between ISC and other agencies

The different operating requirements of the International Seismological Centre (ISC) from those of the National Earthquake Information Service of the US Geological Survey(NEIS), and of the prototype International Data Center to monitor the Comprehensive Test Ban Treaty (pIDC), result in some discrepancies between earthquake locations computed by the three agencies. For larger events recorded by many stations the differences are small, but for some smaller events differences in location of up to 20^° may occur. The largest discrepancies are found for small events in areas where later analysis by ISC has the benefit of additional readings from regional seismograph networks and where ISC has made a different interpretation of the station readingsavailable to pIDC and NEIS. We identify regions where such discrepancies occur most frequently, and give some examples for which the augmented data set of ISC has resulted in significant improvement for specific earthquakes. NEIS and, particularly, pIDC produce their results more speedily than ISC, and these form a valuable starting point for the later, more complete ISC analysis, which is commonly considered the most definitive compilation of global earthquake information.     

Elicitation of Expert Judgments of Aerosol Forcing

A group of twenty-four leading atmospheric and climate scientists provided subjective probability distributions that represent their current judgment about the value of planetary average direct and indirect radiative forcing from anthropogenic aerosols at the top of the atmosphere. Separate estimates were obtained for the direct aerosol effect, the semi-direct aerosol effect, cloud brightness (first aerosol indirect effect), and cloud lifetime/distribution (second aerosol indirect effect). Estimates were also obtained for total planetary average forcing at the top of the atmosphere and for surface forcing. Consensus was strongest among the experts in their assessments of the direct aerosol effect and the cloud brightness indirect effect. Forcing from the semi-direct effect was thought to be small (absolute values of all but one of the experts' best estimates were ≤0.5 W/m²). There was not agreement about the sign of the best estimate of the semi-direct effect, and the uncertainty ranges some experts gave for this effect did not overlap those given by others. All best estimates of total aerosol forcing were negative, with values ranging between −0.25 W/m² and −2.1 W/m². The range of uncertainty that a number of experts associated with their estimates, especially those for total aerosol forcing and for surface forcing, was often much larger than that suggested in 2001 by the IPCC Working Group 1 summary figure (IPCC, 2001).