Contrasting development of Pleistocene warm temperature regimes across the Arctic

Late Pleistocene records from the North Atlantic characterize intervals of major interglacials as times of comparable ocean warmth (+-1-2°C) due to enhanced poleward flow of warm North Atlantic surface waters. A number of recent observations and interpretations from various climate archives would imply varying impacts on the arctic environment during older interglacials. Among warm periods of the past 500 ka, marine isotope stage 11 (MIS 11) is often named as the prominent interglacial phase with a particularly tight global-scale climate connection. For Greenland, it was even suggested that the ice sheet was so strongly reduced in size that trees were able to thrive. And as noted in records from Lake El’gygytgyn in NE Siberia, average temperatures and precipitations exceeded those of the Holocene by far. Indeed, this interpretation of a rather moist and warm climate over Siberia seems to be in line also with assumptions concluded from other lake (Baikal) and speleothem records. In terms of meridional transfer of ocean-atmosphere heat across the North Atlantic, the Nordic Seas comprise the major gateway to the Arctic Ocean. By investigating in detail the oceanic surface ocean warmth during MIS 11 we cannot identify overly enhanced heat flow from the North Atlantic into the Arctic during this interglacial interval. As further deduced from our data, subsequent warm periods (e.g., MIS 5e and MIS 1) appear to have had significantly warmer surface ocean conditions than MIS 11. Moreover, sediment records from close to Greenland would imply a very active eastern ice sheet margin throughout MIS11 with regard to iceberg release rates and occurrence of sea ice. It is therefore proposed that the observation of rather cold surface conditions in the Nordic Seas but comparatively warm temperature regime over the Pacific side of the Arctic either resulted in or caused a distinct cross-arctic climate contrast. That situation significantly changed atmospheric circulation patterns with effects on arctic albedo and associated feedback factors, such as seasonal sea ice extent as well as circum-arctic vegetation, snow cover, and moisture supply

Annual changes in Arctic fjord environment and modern benthic foraminiferal fauna:Evidence from Kongsfjorden, Svalbard

The relationships between modern Arctic benthic foraminifera and their ecological controls, along with their sensitivity to rapid environmental changes, is still poorly understood. This study examines how modern benthic foraminifera respond to annual environmental changes in the glaciated Arctic fjord Kongsfjorden, western Svalbard. Large environmental gradients due to the inflow of warm and saline Atlantic Water and the influence of tidewater glaciers characterise the fjord hydrography. A transect of six multi-corer stations, from the inner to the outer fjord, was sampled in the late summers of 2005 to 2008 to study the distribution of living (rose Bengal stained) benthic foraminifera. Physical properties of the water masses were measured concurrently. In general, nearly the entire Kongsfjorden region was dominated by ubiquitous N. labradorica foraminiferal assemblage that successfully exploited the local food resources and thrived particularly well in the presence of Atlantic-derived Transformed Atlantic Water (TAW). Further, the annual investigation revealed that Kongsfjorden underwent large interannual hydrological changes during the studied years related to variable inflow of warm and saline Atlantic Water. This led to a strong fauna variability particularly at the two marginal sites: the glacially influenced inner fjord and marine influenced shelf region. We also observed significant species shift from the ‘cold’ to ‘warm’ years and an expansion of widespread and sub-arctic to boreal species into the fjord

Experimental investigation of the effects of add-on fan radiators on heat output and indoor air temperature

Conventional panel radiators are widely used to satisfy indoor heating demands thanks to the heat transfer from the radiator by natural convection and radiation. To increase the heat output from an existing radiator without increasing the supply temperature or replacing the radiator with bigger ones, fans can be mounted below the radiator and this installation carries out heat transfer from the radiator by forced convection. The heat output increases and the changes in the rates of heat transfer mechanisms of these radiators, which are called add-on fan radiators, were experimentally investigated under different supply temperature and fan speed conditions. In addition, the effects of add-on fan radiators on the air temperature values in the test room were also examined. The results show that the addition of the fan unit increased the heat output from the radiator considerably. Also, more enhancement was observed at lower supply temperature conditions. It was also concluded that although the rate of heat output by natural convection and radiation decreased in add-on fan radiators, the total heat output from the radiator was higher than the conventional radiators due to the heat output arising from forced convection prevent this decrease

Chapter Eight Diatoms: From Micropaleontology to Isotope Geochemistry

International audienc

North Atlantic sea surface temperatures and their relation to the North Atlantic Oscillation during the last 230 years

August Sea Surface Temperatures (aSSTs) based on fossil diatom assemblages are generated with 2 year average resolution from a 230-year-long sediment core (Rapid 21-12B), from the Reykjanes Ridge in the subpolar North Atlantic. The results indicate a warming trend of ~0.5°C of the surface waters at the Reykjanes Ridge for the last 230 years. Superimposed on this warming trend there is a multidecadal to decadal aSST variability of up to 1°C. The interval from the 1770s to the 1830s represents the coldest period, whereas ~1860–1880 represents the warmest period during the last 230 years. The last 25 years is characterized by a warming trend showing strong decadal aSST variability with several warm years, but also the coldest years since the 1820s. The time of these cold years in the mid-1970s, -1980s and -1990s correspond with the documented great salinity anomalies (GSA) in the North Atlantic suggesting increased fluxes of cold, low-salinity waters from the Arctic during the last decades. The aSST record and the August North Atlantic Oscillation (aNAO) index show similar multidecadal-scale variability indicating a close coupling between the oceanic and atmospheric patterns. The aSST record shows a negative correlation with the aNAO indicating cold aSST during the positive aNAO trend and vice versa. Results suggest that the wind driven variation in volume fluxes of the North Atlantic surface waters could be the major mechanism behind the observed relationship