On the thermodynamic efficiency of steady atmospheric circulations     

Dr. Hans Ertel  Dr. Hilding Köhler 《Pure and Applied Geophysics》1948,13(3-4):102-108

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Luminescence Variations in Fast-Growing Stalagmites from Uppsala, Sweden     

Hanna Sofia Sundqvist  y Baker  Karin Holmgren 《Geografiska Annaler: Series A, Physical Geography》2005,87(4):539-548

Two fast‐growing stalagmites from a cellar vault in Uppsala, southeast Sweden, are analysed for their luminescent properties. The results indicate that variations in luminescence intensity in the stalagmites are annual. Due to problems in finding a suitable absolute dating method this assumption cannot yet be firmly tested; however, results from radiocarbon dating of one of the stalagmites do not contradict the proposal that the laminae are annual. If so, the speleothems have been growing for 10–15 years with a growth rate of 3–8 mm per year, which is a similar rate to other fast‐growing speleothems in Great Britain that have formed from the reaction of lime mortar and carbon dioxide. It is likely that the assumed annual laminae of the luminescence record represent a flush of organic material.  相似文献   

On vertical interpolation and truncation in connexion with use of sigma system models     

Hilding Sundqvist 《大气与海洋》2013,51(1):37-52

Abstract

The Mackenzie Shelf in the Canadian Beaufort Sea receives large amounts of freshwater runoff in winter and, yet, it also produces ventilating water masses by brine rejection from growing ice. We examine physical and chemical data to see how these contradictory processes can occur juxtaposed on the shelf. Measurements of salinity and δ¹⁸O both from ice cores and the water column are used to infer the separation into two convective regimes due to the under‐ice topography of the system of large pressure ridges that forms at the boundary between landfast ice and pack ice. Outside this ridge system the ice cover is subject to frequent openings due to offshore ice motion. The inner regime is thus dominated by the impoundment of Mackenzie River water, whereas the outer regime is subject to brine enhancement. This paper compares freezing processes and system evolution for these two regimes in winter.  相似文献   

UVMag: stellar formation,evolution, structure and environment with space UV and visible spectropolarimetry     

C. Neiner  D. Baade  A. Fullerton  C. Gry  G. Hussain  A. Lèbre  J. Morin  P. Petit  J. O. Sundqvist  A. ud-Doula  A. A. Vidotto  G. A. Wade  The UVMag consortium 《Astrophysics and Space Science》2014,354(1):215-227

Important insights into the formation, structure, evolution and environment of all types of stars can be obtained through the measurement of their winds and possible magnetospheres. However, this has hardly been done up to now mainly because of the lack of UV instrumentation available for long periods of time. To reach this aim, we have designed UVMag, an M-size space mission equipped with a high-resolution spectropolarimeter working in the UV and visible spectral range. The UV domain is crucial in stellar physics as it is very rich in atomic and molecular lines and contains most of the flux of hot stars. Moreover, covering the UV and visible spectral domains at the same time will allow us to study the star and its environment simultaneously. Adding polarimetric power to the spectrograph will multiply tenfold the capabilities of extracting information on stellar magnetospheres, winds, disks, and magnetic fields. Examples of science objectives that can be reached with UVMag are presented for pre-main sequence, main sequence and evolved stars. They will cast new light onto stellar physics by addressing many exciting and important questions. UVMag is currently undergoing a Research & Technology study and will be proposed at the forthcoming ESA call for M-size missions. This spectropolarimeter could also be installed on a large UV and visible observatory (e.g. NASA’s LUVOIR project) within a suite of instruments.  相似文献   

Speleothem evidence for late Holocene climate variability and floods in Southern Greece     

Martin Finné  Miryam Bar-Matthews  Karin Holmgren  Hanna S. Sundqvist  Ilias Liakopoulos  Qiong Zhang 《Quaternary Research》2014

We present stable isotope data (δ¹⁸O, δ¹³C) from a detrital rich stalagmite from Kapsia Cave, the Peloponnese, Greece. The cave is rich in archeological remains and there are reasons to believe that flooding of the cave has directly affected humans using the cave. Using a combination of U–Th and ¹⁴C dating to constrain a site-specific correction factor for (²³²Th/²³⁸U) detrital molar ratio, a linear age model was constructed. The age model shows that the stalagmite grew during the period from ca. 950 BC to ca. AD 830. The stable oxygen record from Kapsia indicates cyclical changes of close to 500 yr in precipitation amount, with rapid shifts towards wetter conditions followed by slowly developing aridity. Superimposed on this signal, wetter conditions are inferred around 850, 700, 500 and 400–100 BC, and around AD 160–300 and AD 770; and driest conditions are inferred to have occurred around 450 BC, AD 100–150 and AD 650. Detrital horizons in the stalagmite indicate that three major floods took place in the cave at 500 BC, 70 BC and AD 450. The stable carbon isotope record reflects changes in biological activity being a result of both climate and human activities.  相似文献