Cold-water corals and hydrochemistry - is there a unifying link?

Physical and chemical parameters were measured in five different regions of the Northeast Atlantic with knownoccurrences of cold-water coral reefs and mounds and in the Mediterranean, where these corals form livingcarpets over existing morphologies. In this study we analyzed 282 bottom water samples regarding delta13CDIC,delta18O, and DIC. The hydrochemical data reveal characteristic patterns and differences for cold-water coralsites with living coral communities and ongoing reef and mound growth at the Irish and Norwegian sites. Whilethe localities in the Mediterranean, in the Gulf of Cadiz, and off Mauritania show only patchy coral growth onmound-like reliefs and various substrates.The analysis of delta13C/delta18O reveals distinct clusters for the different regions and the respective bottomwater masses bathing the delta18O, and especially between delta13CDIC and DIC shows that DIC is a parameterwith high sensitivity to the mixing of bottom water masses. It varies distinctively between sites with livingreefs/mounds and sites with restricted patchy growth or dead corals. Results suggest that DIC and delta13CDICcan provide additional insights into the mixing of bottom water masses.Prolific cold-water coral growth forming giant biogenic structures plot into a narrow geochemical windowcharacterized by a variation of delta13CDIC between 0.45 and 0.79 per mille being associated with the water masshaving a density of sigma-theta of 27.50.15 kg m-3

Alternative global Cretaceous paleogeography

Plate tectonic reconstructions for the Cretaceous have assumed that the major continental blocks—Eurasia, Greenland, North America, South America, Africa, India, Australia, and Antarctica—had separated from one another by the end of the Early Cretaceous, and that deep ocean passages connected the Pacific, Tethyan, Atlantic, and Indian Ocean basins. North America, Eurasia, and Africa were crossed by shallow meridional seaways. This classic view of Cretaceous paleogeography may be incorrect. The revised view of the Early Cretaceous is one of three large continental blocks— North America–Eurasia, South America–Antarctica-India-Madagascar-Australia; and Africa—with large contiguous land areas surrounded by shallow epicontinental seas. There was a large open Pacific basin, a wide eastern Tethys, and a circum- African Seaway extending from the western Tethys (“Mediterranean”) region through the North and South Atlantic into the juvenile Indian Ocean between Madagascar-India and Africa. During the Early Cretaceous the deep passage from the Central Atlantic to the Pacific was blocked by blocks of northern Central America and by the Caribbean plate. There were no deep-water passages to the Arctic. Until the Late Cretaceous the Atlantic-Indian Ocean complex was a long, narrow, sinuous ocean basin extending off the Tethys and around Africa. Deep passages connecting the western Tethys with the Central Atlantic, the Central Atlantic with the Pacific, and the South Atlantic with the developing Indian Ocean appeared in the Late Cretaceous. There were many island land areas surrounded by shallow epicontinental seas at high sea-level stands

Research perspectives of sediment waves and drifts: Monitors of global change in deepwater circulation

The purpose of this special section in Paleoceanography is to present interdisciplinary approaches for contributing to the reconstruction of ocean circulation and its response to climate changes. A high-priority objective for understanding the causes and mechanisms of climate change is the monitoring of past ocean circulation and oceanic heat and nutrient transport. Lehman and Keigwin [1992] have shown that cooling, for example, during the younger Dryas event, may have culminated in a cessation of the oceans conveyor circulation. The cooling in the North Atlantic was apparently the result of reduced northward heat transport in the upper water masses of the North Atlantic conveyor belt. In contrast, intervals with a strong surface and deepwater circulation were marked by a high northward heat transport. For the understanding of the causes and the timing of such rapid,highfrequency events, marine records of high deposition ratecores are needed. These cores should provide evidence for changes in abyssal circulation and heat transport, as well as arecord of surface and deepwater characteristics. The sediment drifts of the North Atlantic and in other ocean basins are one of the major targets for the recovery of sediments with high deposition rates (>10 cm/kyr) and for reconstructing the role of both intermediate and deepwater production in the conveyor belt, that is drawing low-latitude heat northward. We stress the need for international programs targeting high deposition rate areas on sediment drifts and sediment waves in order to understand (1) the evolution of the conveyor belt and (2) its dynamics and variability. The North Atlantic, where sediment drifts are concentrated, will provide ideal study areas with time resolutions comparable to those of ice core records but with records linked directly to the record of changing bottom water flow. Therefore one can address the changes in circulation, heat and carbon budget on high and ultrahigh resolution records

The curious activity in the nucleus of NGC 4151: jet interaction causing variability?

A key characteristic of many active galactic nuclei (AGNs) is their variability, but its origin is poorly understood, especially in the radio domain. Williams et al. (2017) reported a ∼50 per cent increase in peak flux density of the AGN in the Seyfert galaxy NGC 4151 at 1.5 GHz with the e-MERLIN array. We present new high-resolution e-MERLIN observations at 5 GHz and compare these to archival MERLIN observations to investigate the reported variability. Our new observations allow us to probe the nuclear region at a factor three times higher resolution than the previous e-MERLIN study. We separate the core component, C4, into three separate components: C4W, C4E, and X. The AGN is thought to reside in component C4W, but this component has remained constant between epochs within uncertainties. However, we find that the Eastern-most component, C4E, has increased in peak flux density from 19.35 ± 1.10 to 37.09 ± 1.86 mJy beam−1, representing an 8.2σ increase on the MERLIN observations. We attribute this peak flux density increase to continue interaction between the jet and the emission line region (ELR), observed for the first time in a low-luminosity AGNs such as NGC 4151. We identify discrete resolved components at 5 GHz along the jet axis, which we interpret as areas of jet–ELR interaction

Western Indian Ocean marine and terrestrial records of climate variability: a review and new concepts on land-ocean interactions since AD 1660

We examine the relationship between three tropical and two subtropical western Indian Ocean coral oxygen isotope time series to surface air temperatures (SAT) and rainfall over India, tropical East Africa and southeast Africa. We review established relationships, provide new concepts with regard to distinct rainfall seasons, and mean annual temperatures. Tropical corals are coherent with SAT over western India and East Africa at interannual and multidecadal periodicities. The subtropical corals correlate with Southeast African SAT at periodicities of 16–30 years. The relationship between the coral records and land rainfall is more complex. Running correlations suggest varying strength of interannual teleconnections between the tropical coral oxygen isotope records and rainfall over equatorial East Africa. The relationship with rainfall over India changed in the 1970s. The subtropical oxygen isotope records are coherent with South African rainfall at interdecadal periodicities. Paleoclimatological reconstructions of land rainfall and SAT reveal that the inferred relationships generally hold during the last 350 years. Thus, the Indian Ocean corals prove invaluable for investigating land–ocean interactions during past centuries

A review of elliptical and disc galaxy structure, and modern scaling laws

A century ago, in 1911 and 1913, Plummer and then Reynolds introduced their models to describe the radial distribution of stars in `nebulae'. This article reviews the progress since then, providing both an historical perspective and a contemporary review of the stellar structure of bulges, discs and elliptical galaxies. The quantification of galaxy nuclei, such as central mass deficits and excess nuclear light, plus the structure of dark matter halos and cD galaxy envelopes, are discussed. Issues pertaining to spiral galaxies including dust, bulge-to-disc ratios, bulgeless galaxies, bars and the identification of pseudobulges are also reviewed. An array of modern scaling relations involving sizes, luminosities, surface brightnesses and stellar concentrations are presented, many of which are shown to be curved. These 'redshift zero' relations not only quantify the behavior and nature of galaxies in the Universe today, but are the modern benchmark for evolutionary studies of galaxies, whether based on observations, N-body-simulations or semi-analytical modelling. For example, it is shown that some of the recently discovered compact elliptical galaxies at 1.5 < z < 2.5 may be the bulges of modern disc galaxies.Comment: Condensed version (due to Contract) of an invited review article to appear in "Planets, Stars and Stellar Systems"(www.springer.com/astronomy/book/978-90-481-8818-5). 500+ references incl. many somewhat forgotten, pioneer papers. Original submission to Springer: 07-June-201

Galaxy bulges and their massive black holes: a review

With references to both key and oft-forgotten pioneering works, this article starts by presenting a review into how we came to believe in the existence of massive black holes at the centres of galaxies. It then presents the historical development of the near-linear (black hole)-(host spheroid) mass relation, before explaining why this has recently been dramatically revised. Past disagreement over the slope of the (black hole)-(velocity dispersion) relation is also explained, and the discovery of sub-structure within the (black hole)-(velocity dispersion) diagram is discussed. As the search for the fundamental connection between massive black holes and their host galaxies continues, the competing array of additional black hole mass scaling relations for samples of predominantly inactive galaxies are presented.Comment: Invited (15 Feb. 2014) review article (submitted 16 Nov. 2014). 590 references, 9 figures, 25 pages in emulateApJ format. To appear in "Galactic Bulges", E. Laurikainen, R.F. Peletier, and D.A. Gadotti (eds.), Springer Publishin