Nitrogen isotope variations along the northeast Pacific margin

Glacial-interglacial changes in sedimentary d15N over the last 120 kyr display a remarkably similar pattern in timing and amplitude in core records extending from the denitrification zone in the eastern tropical North Pacific (ETNP), where subsurface denitrification is active, to the Oregon margin, where no denitrification occurs today. Low d15N values (4-6 per mil) generally characterize glacial stages 2 and 4, and higher d15N values (7-10 per mil) are representative of the Holocene, millennial-scale periods within stage 3, and stage 5. The inferred synchroneity of d15N variations along the entire margin implies that the nitrate isotopic signal produced in the oxygen-poor subsurface waters in the ETNP is rapidly advected northward and recorded at sites far beyond the boundaries of the modern denitrification zone. Similar to d15N, primary production indicators (percent Corg, Ba/Al, and percent opal) show glacial-interglacial as well as millennial-scale variations along the NE Pacific margin, with higher primary production during warm periods. However, the relative phasing between d15N and paleoproduction tracers within individual records changes latitudinally. Whereas d15N and primary production vary approximately synchronously in the midlatitudes, production lags d15N in the ETNP by several kiloyears. This lag calls for a new understanding of the processes driving denitrification in the ETNP. We suggest that oxygen input by the Equatorial Undercurrent as well as local organic matter flux controls denitrification rates in the ETNP. Moreover, the differences in relative timing point to a time-transgressive development of upwelling-favorable winds along the NE Pacific margin after the last glaciation, with those in the north developing several kiloyears earlier.

Half-degree gridded nitrogen and phosphorus fertilizer use for global agriculture production during 1900-2013

In addition to enhance agricultural productivity, synthetic nitrogen (N) and phosphorous (P) fertilizer application in croplands dramatically altered global nutrient budget, water quality, greenhouse gas balance, and their feedbacks to the climate system. However, due to the lack of geospatial fertilizer input data, current Earth system/land surface modeling studies have to ignore or use over-simplified data (e.g., static, spatially uniform fertilizer use) to characterize agricultural N and P input over decadal or century-long period. We therefore develop a global time-series gridded data of annual synthetic N and P fertilizer use rate in croplands, matched with HYDE 3,2 historical land use maps, at a resolution of 0.5º latitude by longitude during 1900-2013. Our data indicate N and P fertilizer use rates increased by approximately 8 times and 3 times, respectively, since the year 1961, when IFA (International Fertilizer Industry Association) and FAO (Food and Agricultural Organization) survey of country-level fertilizer input were available. Considering cropland expansion, increase of total fertilizer consumption amount is even larger. Hotspots of agricultural N fertilizer use shifted from the U.S. and Western Europe in the 1960s to East Asia in the early 21st century. P fertilizer input show the similar pattern with additional hotspot in Brazil. We find a global increase of fertilizer N/P ratio by 0.8 g N/g P per decade (p< 0.05) during 1961-2013, which may have important global implication of human impacts on agroecosystem functions in the long run. Our data can serve as one of critical input drivers for regional and global assessment on agricultural productivity, crop yield, agriculture-derived greenhouse gas balance, global nutrient budget, land-to-aquatic nutrient loss, and ecosystem feedback to the climate system.

(Table 1) Alkenone concentration, UK'37 index and derived sea surface temperatures for ODP Site 167-1020

Uk'37 sea-surface temperature (SST) estimates obtained at ~2.5-k.y. resolution from Ocean Drilling Program Site 1020 show glacial-interglacial cyclicity with an amplitude of 7°-10°C over the last 780 k.y. This record shows a similar pattern of variability to another alkenone-based SST record obtained previously from the Santa Barbara Basin. Both records show that oxygen isotope Stage (OIS) 5.5 was warmer by ~3°C relative to the present and that glacial Uk'37 temperatures warm in advance of deglaciation, as inferred from benthic d18O records. The alkenone-based SST record at Site 1020 is longer than previously published work along the California margin. We show that warmer than present interglacial stages have occurred frequently during the last 800 k.y. Alkenone concentrations, a proxy for coccolithophorid productivity, indicate that sedimentary marine organic carbon content has also varied significantly over this interval, with higher contents during interglacial periods. A baseline shift to warmer SST and greater alkenone content occurs before OIS 13. We compare our results with those from previous multiproxy studies in this region and conclude that SST has increased by ~5°C since the last glacial period (21 ka). Our data show that maximum alkenone SSTs occur simultaneously with minimum ice volume at Site 1020, which is consistent with data from farther south along the margin. The presence of sea ice in the glacial northeast Pacific, the extent of which is inferred from locations of ice-rafted debris, provides further support for our notion of cold surface water within the northern California Current system, averaging 7°-8°C cooler during peak glacial conditions. The cooling of surface water during glacial stages most likely did not result from enhanced upwelling because alkenone concentrations and terrestrial redwood pollen assemblages are consistently lower during glacial periods.

Pollen record from Eifel maar

A new interglacial pollen sequence from the Döttinger dry maar in the Eifel region of the Rheinish Schield is presented. Palynology is used to correlated to several classical north German Holsteinian sites. The lake sediments reveal the complete interglacial and also 60 m of laminated sediments from the glacial preceding the Holsteinian. The interglacial section indicates limnic conditions in its lower part and telmatic conditions in its upper part with an intermediate episode of peat formation. Ash layers document internsive volcansim during the interglacial in the Eifel region. Some of the north German Holsteinian sites reval spikes of high abundance of Pinus, Beutal and Poaceae and/or setbacks of more demanding taxa during the interglacial, often interpreted as cold events. The Döttingen profile shows similar pattern, but with little response from the thermophilous pollen taxa. In the Döttingen sequence these vegetation 'anomalies' are preceded, or accompanied by phases of active volcanism. The role/interaction of climate and/or volcanism as a likely cause for these vegetation 'anomalies' ist still to be quantified.

Experimental data on photophysiology and growth rates of the invasive foraminifera Amphistegina lobifera showing high thermal tolerance from the Eastern Mediterranean and the Gulf of Aqaba

Invasive species allow an investigation of trait retention and adaptations after exposure to new habitats. Recent work on corals from the Gulf of Aqaba (GoA) shows that tolerance to high temperature persists thousands of years after invasion, without any apparent adaptive advantage. Here we test whether thermal tolerance retention also occurs in another symbiont-bearing calcifying organism. To this end, we investigate the thermal tolerance of the benthic foraminifera Amphistegina lobifera from the GoA (29° 30.14167 N 34° 55.085 E) and compare it to a recent "Lessepsian invader population" from the Eastern Mediterranean (EaM) (32° 37.386 N, 34°55.169 E). We first established that the studied populations are genetically homogenous but distinct from a population in Australia, and that they contain a similar consortium of diatom symbionts, confirming their recent common descent. Thereafter, we exposed specimens from GoA and EaM to elevated temperatures for three weeks and monitored survivorship, growth rates and photophysiology. Both populations exhibited a similar pattern of temperature tolerance. A consistent reduction of photosynthetic dark yields was observed at 34°C and reduced growth was observed at 32°C. The apparent tolerance to sustained exposure to high temperature cannot have a direct adaptive importance, as peak summer temperatures in both locations remain <32°C. Instead, it seems that in the studied foraminifera tolerance to high temperature is a conservative trait and the EaM population retained this trait since its recent invasion. Such pre-adaptation to higher temperatures confers A. lobifera a clear adaptive advantage in shallow and episodically high temperature environments in the Mediterranean under further warming.

Distribution of heavy minerals in sediment cores from the Laptev Sea continental margin and the central Arctic Ocean

Focussing on heavy-mineral associations in the Laptev-Sea continental margin area and the eastern Arctic Ocean, 129 surface sediment samples, two short and four long gravity cores have been studied. By means of the accessory components, heavy-mineral associations of surface sediment samples from the Laptev-See continental slope allowed the distinction into two different mineralogical provinces, each influenced by fluvial input of the Siberian river Systems. Transport pathways via sea ice from the shallow shelf areas into the Arctic Ocean up to the final ablation areas of the Fram Strait can be reconstructed by heavy-mineral data of surface sediments from the central Arctic Ocean. The shallow shelf of the Laptev Sea seems to be the most important source area for terrigenous material, as indicated by the abundant occurence of amphiboles and clinopyroxenes. Underneath the mixing Zone of the two dominating surface circulation Systems, the Beaufort- Gyre and Transpolar-Drift system, the imprint of the Amerasian shelf regions up to the Fram Strait is detectable because of a characteristical heavy-mineral association dominated by detrital carbonate and opaque minerals. Based On heavy-mineral characteristics of the potential circum-Arctic source areas, sea-ice drift, origin and distribution of ice-rafted material can be reconstructed during the past climatic cycles. Different factors controlling the transport of terrigenous material into the Arctic Ocean. The entrainment of particulate matter is triggered by the sea level, which flooded during highs and lows different regions resulting in the incorporation of sediment from different source areas into the sea ice. Additionally, the fluvial input even at low stands of sea level is responsible for the delivery of material of distinct sources for entrainment into the sea ice. Glacials and interglacials of climate cycles of the last 780 000 years left a characteristical signal in the central Arctic Ocean sediments caused by the ice- rafted material from different sources in the circum-Arctic regions and its change through time. Changes in the heavy-mineral association from an amphibole-dominated into a garnet-epidote-assemblage can be related to climate-related changes in source areas and directions of geostrophic winds, the dominating drive of the sea-ice drift. During Marine Isotope Stage (MIS) 6, the central Arctic Ocean is marked by an heavy-mineral signal, which occurs in recent sediments of the eastern Kara Sea. Its characteristics are high amounts of epidote, garnet and apatite. On the other hand, during the Same time interval a continuous record of Laptev Sea sediments is documented with high contents of amphiboles on the Lomonosov Ridge near the Laptev Sea continental slope. A nearly similar Pattern was detected in MIS 5 and 4. Small-scale glaciations in the Putorana-mountains and the Anabar-shield may have caused changes in the drainage area of the rivers and therefore a change in fluvial input. During MIS 3, the heavy-mineral association of central Arctic sediments show similar patterns than the Holocene mineral assemblage which consists of amphiboles, ortho- and clinopyroxenes with a Laptev Sea source. These minerals are indicating a stable Transpolar-Drift system similar to recent conditions. An extended influence of the Beaufort Gyre is only recognized, when sediment material from the Amerasian shelf areas reached the core location PS2757-718 during Termination Ib. Based On heavy-mineral data from Laptev-Sea continental slope Core PS2458-4 the paleo-sea-ice drift in the Laptev Sea during 14.000 years was reconstructed. During Holocene sea-level rise, the bathymetrically deeper parts of the Western shelf were flooded first. At the beginning of the Atlantic stage, nearly the entire shelf was marine influenced by fully marine conditions and the recent surface circulation was established.

Chemical composition of manganese deposits (Birnessite) from Scotland

A manganese pan near Birness contains grains of an optically uniaxial negative mineral near (Na0.7Ca0.3)Mn7O14·2·8H2O, giving an X-ray powder pattern similar to that of synthetic materials described as 'manganous manganite' and delta-MnO2. Material giving a similar pattern has been described from a natural occurrence in Canada, but no mineral name was assigned; the name birnessite is now proposed. The mineral is probably formed by air-oxidation of manganous oxides under alkaline conditions.