an effect of dissolved nutrient concentrations on alkenone based temperature estimates the ratio of 37 carbon diunsaturated to diunsaturated and triunsaturated alkenones uk 37 produced by some haptophytes is widely used as a proxy for past sea surface temperatures however our isothermal culturing experiments with emiliania huxleyi clone ccmp372 show uk 37 values to also vary with nutrient availability and cell division rate these results provide a reasonable explanation for large isothermal variation in uk 37 values of single coccolithophorid strains grown in culture they also suggest that alkenone based estimates of past sea surface temperatures may have been influenced by dissolved nutrient concentrations as well as by temperature

a meteorological analysis of the 2013 alberta flood antecedent large scale flow pattern and synoptic dynamic characteristics abstractthe 19 21 june 2013 alberta flood was the costliest cad 6 billion natural disaster in canadian history the flood was caused by a combination of above normal spring snowmelt in the canadian rockies large antecedent precipitation and an extreme rainfall event on 19 21 june that produced rainfall totals of 76 mm in calgary and 91 mm in the foothills as is typical of flash floods along the front range of the rocky mountains rapidly rising streamflow proceeded to move downhill eastward into calgary a meteorological analysis traces an antecedent rossby wave train across the north pacific ocean starting with intense baroclinic development over east asia on 11 june subsequently downstream rossby wave development occurred across the north pacific a 1032 hpa subtropical anticyclone located northeast of hawaii initiated a southerly atmospheric river into alaska which contributed to the development of a cutoff anticyclone over alaska and a rex block ridge to the north cyclone to the south in

a new mechanistic model for organic carbon fluxes in the ocean based on the quantitative association of poc with ballast minerals abstract in simulation studies of the ocean s role in the global carbon cycle predicting the depth distribution for remineralization of particulate organic carbon poc is of particular importance following sarmiento et al global biogeochemical cycles 7 1993 417 most simulation models have the power law curve of martin et al deep sea research 34 1987 267 for this purpose the martin et al curve is an empirical fit to data most of which is from shallow floating sediment traps using such a fit implies that all the information necessary for prediction is contained in the carbon flux itself so that the organic carbon flux f oc z at any depth z can be predicted from the flux of organic carbon f oc z 0 at some near surface depth z 0 here we challenge this basic premise arguing that fluxes of ballast minerals silicate and carbonate biominerals and dust determine deep water poc fluxes so that a mechanism based model of poc flux must simultaneously predict fluxes of both poc and ballast minerals this assertion is based on the empirical observation that poc fluxes are tightly linked quantitatively to fluxes of ballast minerals in the deep ocean here we develop a model structure that incorporates this observation and fit this model to us jgofs eqpac data this model structure plus the preliminary parameter estimates we have obtained can be used to explore the implications of our model in studies of the ocean carbon cycle

far upstream precursors of heavy precipitation events on the alpine south side this study examines the upper level flow pattern that foreshadows the comparatively frequent co occurrence of heavy precipitation events on the alpine south side together with potential vorticity pv streamers aloft over western europe it is hypothesized that each streamer is itself preceded by a dynamically distinctive and a thermodynamically active flow associated with the space time development and the ultimate breaking over europe of synoptic scale rossby waves the ecmwf european centre for medium range weather forecasts era 40 dataset is used to examine the nature of a streamer s coherent precursor pattern by deriving seasonal composites of refined hovmoller diagrams the upper level pattern of the pv and its gradient and mid tropospheric diabatic heating for the autumn and winter seasons the composites reveal a significant and coherent wave packet precursor signal in the pv field that can be traced back 1 week to the central and eastern pacific contemporaneously the coherent signatures in the composite pv gradient field and diabatic heating fields are conducive to triggering and or supporting the wave signal and also contribute to subsequent downstream wave breaking in spring the composite precursor pv signal appears over and propagates eastward from the atlantic basin and its limited zonal extent is attributed to the lack of a coherent pv waveguide in summer the signal appears essentially in situ in the hovmoller analysis but extends across the atlantic basin in the pv composite results an indication is also provided of the extent to which the composite characteristics are evident in two individual events and note is made of the study s implications for medium range forecasting copyright 2008 royal meteorological society

identification of dissolution patterns in nannofossil assemblages a high resolution comparison of synchronous records from ceara rise odp leg 154 1 fossil nannoplankton assemblages are controlled by both initial plankton production and dissolution throughout the water column and on the seafloor it is usually assumed that dissolution can be identified by subjective visual assessment of preservation state we have tested this by a quantitative comparison of mid pliocene nannofossil assemblages in two closely located odp sites ceara rise sites 926 and 929 both with apparently good preservation but located respectively above and below the lysocline we demonstrate that despite an absence of obvious qualitative preservation differences dissolution has removed perhaps 80 of the assemblage in the sub lysocline site 929 this has produced consistent distortions in the assemblages and artificially enhanced abundance variations patterns of individual species the results provide strong cautions for palaeoceanographic interpretation of nannofossil data and allow us to uniquely extract a dissolution variation record and provide a detailed ranking of dissolution susceptibility of pliocene nannofossils

the morphology of northern hemisphere blocking abstract the morphology of regional blocking in the northern hemisphere is discussed using the 40 yr ecmwf re analysis era 40 dataset and a measure of blocking based on the reversal at storm track latitudes of meridional contrasts on a potential vorticity pv surface representative of the tropopause the focus is on cyclonic and anticyclonic rossby wave breaking that is inherent to the blocking development and the extent to which this is determined by the climatological jet position and the ambient shears more generally the importance of the climatological planetary scale is discussed the approach is mainly through composite behavior but informed by consideration of many individual events a diversity of behavior is found with longitude in both winter and summer and there is a striking reversal of the sense of the wave breaking between the two seasons that is generally consistent with the difference in the jet locations preferred behaviors are found in various regions and seasons and retrogre

long lived rossby wave trains as precursors to strong winter cyclones over europe the statistical connection between strong surface cyclones over europe and long lived upper tropospheric rossby wave trains is examined for the northern hemisphere winter season using 45 years of reanalysis data dates are selected for which the surface pressure anomaly over central europe is below a threshold yielding the 5 of lowest values composites of upper tropospheric meridional wind for these dates including a lead or lag in time display clear signs of a wave train the composite wave train lives for over two weeks and propagates eastward over more than 360 longitude the phase speed of individual lows and highs by contrast is close to zero and the same is true for the composite surface low there is a pronounced northward shift of the wave train as it propagates over the north american east coast although this composite wave train is statistically highly significant there is large scatter about the mean an index is defined that quantifies the similarity of the upper tropospheric meridional wind pattern for an arbitrary date with the composite wave train for a certain lead or lag given large positive values of the index there is an enhanced probability of a strong surface cyclone over central europe a few days later comparison with a previous study focusing on pacific cyclones shows noteworthy differences

alkenone and boron based pliocene pco2 records abstract the pliocene period is the most recent time when the earth was globally significantly 3 c warmer than today however the existing pco2 data for the pliocene are sparse and there is little agreement between the various techniques used to reconstruct palaeo pco2 this disagreement coupled with the general low temporal resolution of the published records does not allow a robust assessment of the role of declining pco2 in the intensification of the northern hemisphere glaciation inhg and a direct comparison to other proxy records are lacking for the first time we use a combination of foraminiferal 11b and organic biomarker alkenone derived carbon isotopes proxies to determine the concentration of atmospheric co2 over the past 5 ma both proxy records show that during the warm pliocene pco2 was between 330 and 400 ppm i e similar to today the decrease to values similar to pre industrial times 275 285 ppm occurred between 3 2 ma and 2 8 ma coincident with the inhg and affirming the link between global climate the cryosphere and pco2

phytoplankton mineralization in the tropical and subtropical atlantic ocean organic carbon fluxes to the deep ocean may be enhanced by association with ballast mineral material such as calcite and opal we made simultaneous measurements of the upper ocean production of calcite calcification opal silicification and organic carbon photosynthesis at 14 stations between 42 s and 49 n in the atlantic ocean these measurements confirm the light dependency of calcification and photosynthesis and the substrate dependency of silicification we estimate that mineralizing phytoplankton represent 5 20 of organic carbon fixation with similar contributions from both coccolithophores and diatoms estimates of average turnover times for calcite and phytoplankton carbon are 3 days indicative of their relatively labile nature by comparison average turnover times for opal and particulate organic carbon are 10 days rapid turnover of calcite suggests an important role for the plankton community in removing calcite from the upper ocean comparison of our surface production rates to sediment trap data confirms that 70 of calcite is dissolved in the upper 2 3 km and only a small proportion of total organic carbon 2 reaches the deep ocean

evolution of the eastern tropical pacific through plio pleistocene glaciation a tropical pacific climate state resembling that of a permanent el nino is hypothesized to have ended as a result of a reorganization of the ocean heat budget 3 million years ago a time when large ice sheets appeared in the high latitudes of the northern hemisphere we report a high resolution alkenone reconstruction of conditions in the heart of the eastern equatorial pacific eep cold tongue that reflects the combined influences of changes in the equatorial thermocline the properties of the thermocline s source waters atmospheric greenhouse gas content and orbital variations on sea surface temperature sst and biological productivity over the past 5 million years our data indicate that the intensification of northern hemisphere glaciation 3 million years ago did not interrupt an almost monotonic cooling of the eep during the plio pleistocene sst and productivity in the eastern tropical pacific varied in phase with global ice volume changes at a dominant 41 000 year obliquity frequency throughout this time changes in the southern hemisphere most likely modulated most of the changes observed

sea surface temperature and productivity records for the past 240 kyr in the arabian sea abstract deep sea sediments of two cores from the western ty93 929 p and the southeastern md900963 arabian sea were used to study the variations of the indian monsoon during previous climatic cycles core ty93 929 p was located between the sw monsoon driven upwelling centres off somalia and oman which are characterized by large seasonal sea surface temperature sst and particle flux changes by contrast core md900963 was situated near the maldives platform an equatorial ocean site with a rather small sst seasonality less than 2 c for both cores we have reconstructed sst variations by means of the unsaturation ratio of c37 alkenones which is compared with the 18o records established on planktonic foraminifera in general the sst records follow the 18o variations with an sst maximum during oxygen isotope stage 5 5 the last interglacial at about 120 130 kyr and a broad sst minimum during isotope stage 4 and 3 3 approximately 40 50 kyr the sst difference between the holocene and the last glacial maximum lgm is of the order of 2 c in both cores the ssts during isotope stage 6 are distinctly higher by 1 2 c than the cold sst minima during the last glacial cycle lgm and stage 3 to reconstruct qualitatively the past productivity variations for the two cores we used the concentrations and fluxes of alkenones and organic carbon together with a productivity index based on coccolith species florisphaera profunda relative abundance within each core there is a general agreement between the different palaeoproductivity proxies in the southeastern arabian sea core md900963 glacial stages correspond to relatively high productivity whereas warm interstadials coincide with low productivity all time series of productivity proxies are dominated by a cyclicity of about 21 23 kyr which corresponds to the insolation precessional cycle a hypothesis could be that the ne monsoon winds were stronger during the glacial stages which induced deepening of the surface mixed layer and injection of nutrients to the euphotic zone by contrast the records are more complicated in the upwelling region of the western arabian sea core ty93 929 p this is partly due to large changes in the sedimentation rates which were higher during specific periods isotope stages 6 5 4 5 2 3 and 2 unlike core md900963 no simple relationship emerges from the comparison between the 18o stratigraphy and productivity records the greater complexity observed for core ty93 929 p could be the result of the superimposition of different patterns of productivity fluctuations for the two monsoon seasons the sw monsoon being enhanced during interglacial periods whereas the ne monsoon was increased during glacial intervals a similar line of reasoning also could help explain the sst records by the superimposition of variations of three components global atmospheric temperature and sw and ne monsoon dynamics

long chain alkenones and alkyl alkenoates and the fossil coccolith record of marine sediments long chain n c37 c39 alkenones and alkyl alkenoates are biological markers for sediment inputs of algae from the class prymnesiophyceae which includes the coccolithophorids these compounds have been recognized in many recent and ancient marine sediments but in only a few living algal species notably the ubiquitous coccolithophorid emiliania huxleyi the proven value of long chain alkenones in palaeotemperature assessment prompts an evaluation of their sedimentary record especially their correspondence with coccolithophorid fossils in ancient marine sediments synthesis of available micropalaeontological and molecular data suggests that morphologically related species of the genera crenalithus dictyococcites emiliania gephyrocapsa pseudoemiliania and reticulofenestra all belonging to the family gephyrocapsaceae were potential biological sources of alkenones and alkyl alkenoates in marine sediments deposited since the eocene 45 ma the occurrence of alkenones in cenomanian and albian sediments devoid of nannofossils may be presumed to reflect contributions from ancestors of the gephyrocapsaceae although an investigation of cretaceous samples containing both coccoliths and alkenones would provide further evidence of this proposed correspondence the combination of palaeontological and molecular chemotaxonomic information offers a novel approach to the evaluation of the phylogenetic lineages that link living and extinct algae

glacial interglacial productivity changes recorded by alkenones and microfossils in late pliocene eastern equatorial pacific and atlantic upwelling zones oceanic upwelling regions are highly productive systems that dominate global ocean new production with important implications for cycling of nitrogen and carbon as well as for climate many proxy methods have been proposed to reconstruct past changes in ocean productivity but uncertainties are associated with the interpretation of each here we report new records of calcareous nannofossil assemblages and siliceous fragment abundance from the late pliocene eastern equatorial pacific and atlantic oceans and compare them with records of total c37 alkenone content from the same sediment samples our data show prominent coherent glacial interglacial timescale variability among all three of these time series with remarkable inter correlation lending support to their interpretation as records of climate coupled changes in productivity we infer that prior to the dominance of the relatively well understood modern alkenone synthesising coccolithophores reticulofenestra spp were the principal calcifying alkenone synthesisers during the late pliocene our records suggest that in upwelling areas on orbital timescales total c37 alkenone concentration tracks productivity not only of the alkenone synthesising coccolithophores but also of the wider phytoplankton community including siliceous diatoms these results lend new significance to pre pleistocene records of total c37 alkenone concentration from upwelling regions particularly those from the eastern equatorial pacific today this region accounts for the majority of global ocean to atmosphere co2 efflux and through biological pump invigoration has the capacity to have contributed significantly to oceanic opal burial and drawdown of atmospheric carbon dioxide the strong correlations that we demonstrate between c37 alkenone concentration and other palaeoproductivity proxies suggest that alkenone accumulation may represent a useful means of inferring pre pleistocene carbon cycle changes

climatically forced organic carbon burial in equatorial atlantic and pacific oceans over the past ten years sedimentary geochemists have noted that climate changes associated with pleistocene glaciations have had a pronounced effect on the rate of organic carbon burial found in the tropical oceans1 4 in particular two to five times higher organic carbon accumulation rates have been observed for the 18 kyr bp glacial maximum than for the holocene in several short sediment cores from both oceans see fig 1 here i present 300 kyr time series for organic carbon mass accumulation rate from four sediment cores two each from the equatorial pacific and atlantic and show that orbital forcing of global climate has strongly affected the rate of organic carbon burial in the equatorial oceans

ocean surface water response to short term climate changes revealed by coccolithophores from the gulf of cadiz ne atlantic and alboran sea w mediterranean the response of coccolithophore assemblages to short term millennial and centennial climatic changes over the last 50 kyr is studied in core m39029 7 from the gulf of cadiz atlantic ocean and core md95 2043 from the alboran sea western mediterranean sea the nannoplankton data are compared with oxygen isotopes u37k sst and other biogeochemical and sedimentological proxies to obtain a new perspective of the paleoceanography and paleoecology of the area during these short term climatic changes coccolithophores indicate that heinrich events he were characterised by the presence of cold low salinity and turbid water masses on both sides of the strait of gibraltar high abundances of the lower photic zone lpz species florisphaera profunda in the gulf of cadiz synchronous with he are interpreted as being an evidence of upper water column stratification on the atlantic side these episodes coincided with input of terrigenous material especially during h2 surface waters during dansgaard oeschger do stadials were also cold and turbid while most of do interstadials were characterised by warm water flora the increase in small placoliths small gephyrocapsa and emiliania huxleyi 4 m which is considered here as a cold water indicator the sharp decrease in large specimens of e huxleyi related to the warming trend in the last deglaciation can be used as a biostratigraphic reference level that marks at least approximately the deglaciation and the beginning of the holocene peaks of f profunda are observed during termination 1 t1 in the alboran sea they are isochronous with the organic rich layer 1 recognised in the western mediterranean in this interval the water column of the region was stratified as a consequence of the global increase in the sea level following the deglaciation quantitative analyses of the coccolithophore assemblage allow us to interpret that coccolithophore production has been higher in the alboran sea than in the gulf of cadiz during the holocene

comparison of logistic regression and random forests techniques for shallow landslide susceptibility assessment in giampilieri ne sicily italy abstract the aim of this work is to define reliable susceptibility models for shallow landslides using logistic regression and random forests multivariate statistical techniques the study area located in north east sicily was hit on october 1st 2009 by a severe rainstorm 225 mm of cumulative rainfall in 7 h which caused flash floods and more than 1000 landslides several small villages such as giampilieri were hit with 31 fatalities 6 missing persons and damage to buildings and transportation infrastructures landslides mainly types such as earth and debris translational slides evolving into debris flows were triggered on steep slopes and involved colluvium and regolith materials which cover the underlying metamorphic bedrock the work has been carried out with the following steps i realization of a detailed event landslide inventory map through field surveys coupled with observation of high resolution aerial colour orthophoto ii identification of landslide source areas iii data preparation of landslide controlling factors and descriptive statistics based on a bivariate method frequency ratio to get an initial overview on existing relationships between causative factors and shallow landslide source areas iv choice of criteria for the selection and sizing of the mapping unit v implementation of 5 multivariate statistical susceptibility models based on logistic regression and random forests techniques and focused on landslide source areas vi evaluation of the influence of sample size and type of sampling on results and performance of the models vii evaluation of the predictive capabilities of the models using roc curve auc and contingency tables viii comparison of model results and obtained susceptibility maps and ix analysis of temporal variation of landslide susceptibility related to input parameter changes models based on logistic regression and random forests have demonstrated excellent predictive capabilities land use and wildfire variables were found to have a strong control on the occurrence of very rapid shallow landslides

relationship between atmospheric blocking and warm season thunderstorms over western and central europe a statistically significant link is presented between atmospheric blocking located over the eastern north atlantic and northern europe and warm season thunderstorm activity over western and central europe lightning data from 2001 to 2014 were used to identify thunderstorm days and blocking events were extracted from the era interim reanalysis using an objective identification algorithm the statistical link between the two phenomena is established through odds ratio analysis two areas one over the eastern part of the north atlantic and one over the baltic sea were identified as locations where blocking influences the occurrence of deep moist convection in parts of western and central europe based on the mean ambient conditions on days with blocking in these two areas well known dynamic and thermodynamic mechanisms supporting or suppressing the development of thunderstorms were confirmed the anticyclonic circulation of a block over the eastern part of the north atlantic leads to a northerly to northwesterly advection of dry and stable air masses into europe on the eastern flank of the block in addition these environmental conditions are on average associated with large scale subsidence of air masses convection inhibiting conditions in contrast the southerly to southwesterly advection of warm moist and unstable air masses on the western flank of a block over the baltic sea results in convection favouring conditions over western and central europe both blocking situations are on average associated with weak wind speeds at mid tropospheric levels and with weak wind shear as a consequence thunderstorms related to atmospheric blocking over the baltic sea tend to be on average less organised

northern hemisphere rossby wave initiation events on the extratropical jet a climatological analysis abstracta climatology of rossby wave initiation rwi events on the northern hemisphere mid latitude jet is compiled by applying an objective rwi identification algorithm to the era interim re analysis dataset in winter rwi events occur most frequently over the northwestern pacific and less often over the north atlantic in summer the total number of rwi events is lower than in winter and the north pacific rwi region shifts towards the tibetan plateau composite analysis of the large scale flow prior to during and after winter north pacific rwi events shows an upstream wave train propagating across asia on the arctic waveguide prior to rwi the composite wave forms on a relatively weak zonal jet streak exhibits a baroclinic structure and is strongly amplified by latent heat release in the warm conveyor belt of a deepening surface cyclone moreover the wave forms in a region of large scale upper level deformation upstream of a pre existing ridge further active tropical convection affects the longit

the impact of wave packets propagating across asia on pacific cyclone development abstract in this paper ecmwf 40 yr reanalysis data have been examined to study the influence of upper level wave packets propagating across asia into the pacific on surface cyclone development over the pacific previous studies have shown that in winter wave packets propagate across asia over two branches a northern branch over siberia and a southern branch along the subtropical jet across southern asia results presented here show that subsequent to the presence of wave packets on either branch the frequency of occurrence of deep cyclones defined as cyclones with central pressure below 960 hpa as well as explosively deepening cyclones those with a deepening rate of 1 bergeron or more are significantly enhanced this enhancement also clearly follows the wave packet eastward as it propagates across the pacific wave packets from the two branches are found to interfere with each other such that if wave packets of the appropriate configuration are present on both the northern and southern branch s

the structure and evolution of heat waves in southeastern australia abstractthe underlying large scale dynamical processes responsible for the development of heat waves in victoria southeastern australia in summer are presented here heat waves are defined as periods of at least three days and two nights for which daily maximum and minimum temperatures exceed the 90th percentile for a particular location and month using a station daily temperature dataset composites of upper level potential vorticity anomalies from the interim ecmwf re analysis era interim reveal that heat waves in southeastern australia are associated with propagating rossby waves which grow in amplitude and eventually overturn the process of overturning generates an upper level anticyclone over southern australia and an upper level trough to the northeast with maximum amplitudes near the tropopause the northerly flow associated with the circulation around the surface anticyclone advects hot air from the continental interior over the southeast of australia leading to extreme surface temperatur

rossby wave packets on the midlatitude waveguide a review abstractrossby wave packets rwps are rossby waves for which the amplitude has a local maximum and decays to smaller values at larger distances this review focuses on upper tropospheric transient rwps along the midlatitude jet stream their central characteristic is the propagation in the zonal direction as well as the transfer of wave energy from one individual trough or ridge to its downstream neighbor a process called downstream development these rwps sometimes act as long range precursors to extreme weather and presumably have an influence on the predictability of midlatitude weather systems the paper reviews research progress in this area with an emphasis on developments during the last 15 years the current state of knowledge is summarized including a discussion of the rwp life cycle as well as rossby waveguides recent progress in the dynamical understanding of rwps has been based in part on the development of diagnostic methods these methods include algorithms to identify and track rwps

physiological impacts on alkenone paleothermometry we conducted isothermal 15 c batch culture experiments with the coccolithophorid emiliania huxleyi strain nepcc 55a to evaluate the extent to which nutrient and light stress contribute to variability in the alkenone unsaturation index u37k alkenone content and composition were constant throughout exponential growth in both experiments when nutrients nitrate and orthophosphate were replete stationary phase nutrient starved cells continued to produce alkenones amassing concentrations alk 3 times higher than those dividing exponentially 1 5 2 pg cell 1 and the u37k of excess alkenone dropped by 0 11 units in contrast 5 days of continuous darkness resulted in a 75 decrease in cellular alk and a significant u37k increase 0 11 units given an established 0 034 unit c response for exponentially growing cells of this strain the observed range of u37k variability at 15 c corresponds to an uncertainty of 3 2 c in predicted growth temperature this level of variability matches that of the global u37k annual mean sea surface temperature calibration for surface marine sediments begging the question what is the physiological condition of alkenone producing cells exported to marine sediments comparison of our laboratory results for a strain of e huxleyi isolated from the subarctic pacific ocean with depth profiles for alkenones in surface waters from two contrasting sites in the northeast pacific ocean suggests that the answer to this question depends on the ocean regime considered a possibility with significant bearing on how stratigraphic u37k records in marine sediments are to be interpreted paleoceanographically

a quantitative assessment of diatom dissolution and late quaternary primary productivity in the eastern equatorial pacific the eastern equatorial pacific eep is an important area for ocean atmosphere carbon exchange and yields different opal accumulation records for sites influenced by equatorial divergence and peru upwelling the divergence zone is characterized by a lower opal accumulation rate during the last glacial compared with the holocene but the reverse is true for the peru upwelling zone as a gauge of opal production versus preservation in the eep differential diatom preservation was investigated via a quantitative four stage preservation index using the vellum of the ubiquitous tropical centric diatom azpeitia nodulifer we find similar dissolution records at both sites from the last glacial maximum lgm through the holocene despite differing accumulation rates implying that production not preservation controlled the accumulation rates thus the increased silica accumulation in the peru upwelling region is related to increased production suggesting higher availability of silica in the photic zone in accord with the silica leakage hypothesis described by matsumoto et al 2002 silicic acid leakage from the southern ocean a possible explanation for glacial atmospheric co global biogeochemical cycles 5 doi 10 1029 2001gb001442 and discussed by richaud et al 2007 furthermore we suggest an ecological control on opal preservation due to silica recycling by diatoms in the water column most likely in the photic zone increased production causes rapid silica recycling and thinner walled frustules resulting in enhanced water column dissolution in this setting diatom dissolution is independent of the rate of accumulation of silica or sediment high opal productivity does not necessarily lead to high preservation as proposed for southern ocean sediments sayles f martin w chase z anderson r 2001 benthic remineralization and burial of biogenic sio2 caco3 organic carbon and detrital material in the southern ocean along a transect at 170 west deep sea research ii 48 4323 4383 our observations are compatible with a production increase in the late deglacial and early holocene as reported by loubere 2001 nutrient and oceanographic changes in the eastern equatorial pacific from the last full glacial to the present global and planetary change 29 77 98 and inferred by spero h and lea d 2002 the cause of carbon isotope maximum events on glacial terminations science 296 522 525 and rickaby r and osborne a 2006 oceanic redistribution of phosphate during the last deglaciation in preparation

identifying rossby wave trains and quantifying their properties a novel method is introduced to automatically identify upper level rossby wave trains and to objectively diagnose their properties based on the envelope of the upper tropospheric meridional wind represented in a hovmoller diagram the algorithm identifies individual rossby wave trains as objects these depend to some extent on user defined parameters the utility of the method is demonstrated in two areas of application first the skill of a particular numerical weather prediction model is analysed for a specific case of a long lived rossby wave train for this purpose a novel diagnostic is designed based on a hovmoller diagram of the rossby wave train objects that contains forecast data with the same lead time throughout the diagram automatically calculated properties of the different forecast rossby wave trains are compared second the climatological behaviour of rossby wave train objects is investigated in long time series from reanalysis data there are preferred regions for the generation and the decay of rossby wave trains and these regions show significant differences for rossby wave trains of different minimum lifetimes in addition there are substantial differences between the seasons

representation of the scandinavia greenland pattern and its relationship with the polar vortex in s2s forecast models the strength of the stratospheric polar vortex is a key contributor to subseasonal prediction during boreal winter anomalously weak polar vortex events can be induced by enhanced vertically propagating rossby waves from the troposphere driven by blocking and wave breaking here we analyse a tropospheric pattern the scandinavia greenland s g pattern associated with both processes the s g pattern is defined as the second empirical orthogonal function eof of mean sea level pressure in the northeast atlantic the first eof is a zonal pattern resembling the north atlantic oscillation we show that the s g pattern is associated with a transient amplification of planetary wavenumber2 and meridional eddy heat flux followed by the onset of a weakened polar vortex which persists for the next 2 months we then analyse 10 different models from the s2s database finding that while all models represent the structure of the s g pattern well some models have a zonal bias with more than the observed variability in their first eof and accordingly less in their second eof this bias is largest in models with the lowest resolution skill in predicting the s g pattern is not high beyond week 2 in any model in contrast to the zonal pattern we find that the relationship between the s g pattern and enhanced eddy heat flux and a weakened polar vortex is initially well represented but significantly decays with lead time in most s2s models our results motivate improved representation of the s g pattern and its stratospheric response at longer lead times for improved subseasonal prediction of the stratospheric polar vortex

the dynamics of euro atlantic blocking onsets the mechanisms leading to euro atlantic blocking are investigated using 31 winters of 500 hpa geopotential height from nmc and ecmwf daily analyses and a 30 000 day perpetual winter run from a simple 3 level quasi geostropic model a composite analysis of the atmospheric flow during days preceding blocking events is carried out it indicates that euro atlantic blocking events have two simultaneous main precursors a high latitude retrograding wave number 1 pattern at planetary scale and an enhanced baroclinic wavetrain travelling across the north atlantic at synoptic scale these phenomena are identified both in observed and in simulated data the nonlinear interactions between small scale large scale and the mean flow during the establishment of the blocking anomaly are examined by a budget analysis of the quasi geostrophic potential vorticity equation these diagnostics demonstrate that wave wave interactions contribute to about 50 of the local amplification of the blocking anomaly while wave mean flow interactions contribute to propagation of the large and small scale anomalies and their phase locking finally the question is addressed as to whether the two precursors are necessary and sufficient conditions for blocking onsets by performing various sets of initial value experiments performed with the quasi geostrophic model these experiments show that the two precursors occur simultaneously but only the synoptic scale baroclinic wavetrain is necessary to trigger euro atlantic blocking

warm upwelling regions in the pliocene warm period 1 given the importance of upwelling processes to coastal productivity and regional climate it is critical to study the role of upwelling regions within the context of global climate change we generated sea surface temperature sst records for the last 5 million years in three important upwelling regions the eastern equatorial pacific the california margin and the peru margin prior to 3 0 ma ssts at all sites were significantly warmer than today by 3 9 c indicating that cold upwelling regions that characterize the modern pacific ocean did not exist in the early pliocene warm period 4 6 to 3 1 ma earth s most recent period of sustained global warmth alkenone phosphorus and organic carbon mass accumulation rate records indicate that changes in productivity and sst were decoupled and that upwelling of nutrient enriched water occurred even when ssts were warm during the early pliocene thus the long term trends in sst are likely explained by changes in the temperature of upwelled water rather than in the strength of upwelling favorable winds alone the fact that gradual cooling of upwelling regions began before the onset of significant northern hemisphere glaciation provides further evidence that the growth of ice sheets and their influence on atmospheric winds alone can not explain the cooling of upwelling regions our results suggest that the long term average ssts of upwelling regions are influenced by global changes in the depth and or temperature of the ventilated thermocline

systematic model forecast error in rossby wave structure diabatic processes can alter rossby wave structure consequently errors arising from model processes propagate downstream however the chaotic spread of forecasts from initial condition uncertainty renders it difficult to trace back from root mean square forecast errors to model errors here diagnostics unaffected by phase errors are used enabling investigation of systematic errors in rossby waves in winter season forecasts from three operational centers tropopause sharpness adjacent to ridges decreases with forecast lead time it depends strongly on model resolution even though models are examined on a common grid rossby wave amplitude reduces with lead 5 days consistent with underrepresentation of diabatic modification and transport of air from the lower troposphere into upper tropospheric ridges and with too weak humidity gradients across the tropopause however amplitude also decreases when resolution is decreased further work is necessary to isolate the contribution from errors in the representation of diabatic processes

proceedings of a workshop on alkenone based paleoceanographic indicators 1 the papers in this theme derive from a workshop on alkenone based paleoceanographic indicators held at the j erik jonsson center of the national academy of sciences in woods hole massachusetts october 3 6 1999 the papers fall into two groups position papers prepared in advance of the workshop by the leaders of six different working groups and reports prepared during and after the workshop by rapporteurs and members of the working groups their publication here is intended to provide a record of the discussions and thus to serve to the paleoceanographic community an overview of the conference and its participants is also provided

factors controlling the flux of organic carbon to the bathypelagic zone of the ocean 1 particle fluxes measured with time series sediment traps deployed below 2000 m at 68 sites in the world ocean are combined with satellite derived estimates of export production from the overlying water to assess the factors affecting the transfer of particulate organic matter from surface to deep water multiple linear regression is used to derive an algorithm suggesting that the transfer efficiency of organic carbon defined as the settling flux of organic carbon normalized to export production increases with the flux of carbonate and decreases with water depth and seasonality the algorithm predicts 80 of the organic carbon transfer efficiency variability in diverse oceanic regions the influence of the carbonate flux suggests that the ballasting effect of this biogenic mineral may be an important factor promoting export of organic carbon to the deep sea by increasing the density of settling particles however the lack of a similar effect for biogenic opal suggests that factors other than particle density also play a role the adverse effect of increasing seasonality on the transfer efficiency of carbon to the deep sea is tentatively attributed to greater biodegradability of organic matter exported during bloom events in high latitude opal dominated regions with high f ratios and seasonality while a higher fraction of net production is exported a higher fraction of the exported organic matter is remineralized before reaching bathypelagic depths on the other hand in warm low latitude carbonate dominated regions with low f ratios and seasonality a higher fraction of the exported organic matter sinks to the deep sea

the relationship between sedimentary organic carbon isotopic composition and organic biomarker compound concentration abstract a study of organic biomarker compounds which could serve as tracers of terrigenous and marine sedimentary organic matter sources was performed on samples from a 208 7 m hydraulic piston core hole dsdp hole 619 from the hemipelagic pigmy basin in the northern gulf of mexico organic carbon normalized concentrations of total long chain c37 c39 alkenones and some individual c27 c29 desmethyl sterols were determined to be useful proportional indicators tracers of preserved marine and terrigenous organic carbon respectively the alkenones whose only known source is marine phytoplankton of the class prymnesiophyceae generally occurred in higher concentrations in interglacial isotope stages 1 and 5a b than in the intervening glacial stages sterols c27 c29 apparently of a dominantly terrigenous origin occurred in lower concentrations during interglacial stages than in glacial stages tracers of both terrigenous and marine organic matter appear to be affected by the differential diagenetic alteration of the biomarker corg ratios as indicated by a simple first order kinetic model the lack of any desmethylor 4a methylsterol which is linearly related to the proportion of marine sedimentary organic matter as scaled by 13corg indicates that either 1 1 sedimentary diagenesis has obscured the biomarker corg vs 13corg record 2 2 phytoplanktonic assemblage changes caused variations in the biomarker corg ratio of the primary input preferential preservation of terrigenous sterols may result in a biased sedimentary record of sterol input which could be misinterpreted as indicating solely terrigenous sterol sources a simple model which characterizes the effects of sedimentary diagenesis on the relationship between corg normalized biomarker ratios and 13corg demonstrates the potential problems of long term differential diagenetic skewing on those tracer records

high amplitude variations in north atlantic sea surface temperature during the early pliocene warm period 1 we provide the first continuous orbital resolution sea surface temperature sst record from the high latitude north atlantic a region critical to understanding the origin of the plio pleistocene ice ages and proximal to regions that became frequently glaciated after 2 7 ma we analyzed sediments from ocean drilling program site 982 over the last 4 ma for their alkenone unsaturation index and compared this surface water signal to a benthic 18o record obtained from the same section we find that while ocean surface temperatures were significantly warmer 6 c than modern temperatures during the early pliocene they were also as variable as those during the late pleistocene a surprising result in light of the subdued variance of oxygen isotopic time series during the interval of 3 5 ma we propose two possible explanations for the high orbital scale sst variability observed either that a strong high latitude feedback mechanism not involving large continental ice sheets alternately cooled and warmed a broad region of the northern high latitudes or that by virtue of its location near the northern margin of the north atlantic drift the site was unusually sensitive to obliquity driven climate shifts on supraorbital time scales a strong sustained cooling of north atlantic ssts 4 5 c occurred from 3 5 to 2 5 ma and was followed by an interval of more modest cooling an additional 1 5 c from 2 5 ma to the present evolutionary orbital scale phase relationships between north atlantic sst and benthic 18o show that sst began to lead 18o significantly coincident with the onset of strong cooling at site 982 3 5 ma we speculate that these changes were related to the growth and subsequent persistence of a greenland ice sheet of approximately modern size through interglacial states

coccolithophores in the equatorial atlantic ocean response to seasonal and late quaternary surface water variability abstract the present study was initiated to ascertain the significance of coccolithophores as a proxy for paleoceanographic and paleoproductivity studies in the equatorial atlantic data from a range of different samples from the plankton surface sediments as well as sediment cores are shown and compared with each other in general the living coccolithophores in the surface and subsurface waters show considerable variation in cell numbers and distribution patterns cell densities reached a maximum of up to 300 103 coccospheres l in the upwelling area of the equatorial atlantic here emiliania huxleyi is the dominant species with relatively high cell numbers whereas umbellosphaera irregularis and umbellosphaera tenuis are characteristic for oligotrophic surface waters although they are observed in high relative abundances these species only occur in low absolute numbers the lower photic zone is dominated by high abundances and considerable cell numbers of florisphaera profunda the geographical distribution pattern of coccoliths in surface sediments reflects the conditions of the overlying surface water masses however abundances of the oligotrophic species umbellosphaera irregularis and umbellosphaera tenuis are strongly diminished causing an increase in relative abundance of the lower photic zone taxa florisphaera profunda and gladiolithus flabellatus during the past 140 000 years the surface water circulation of the equatorial atlantic has changed drastically as can be seen from changes in the coccolithophore species composition absolute coccolith numbers as well as coccolith accumulation rates significant increases in coccolith numbers and accumulation rates is observed in the southern equatorial atlantic during the last glacial interval oxygen isotope stages 2 4 which we attribute to enhanced upwelling intensities and advection of cool nutrient rich waters at this site in the western equatorial atlantic we observe an opposite trend with decreasing numbers of coccoliths during glacial periods which probably is caused by a deepening of the thermocline

a comparison of multiple proxies for export production in the equatorial pacific 1 several commonly used paleoproductivity proxies were compared to evaluate the validity of assumptions and limitations associated with each proxy export production fluxes cexport over glacial interglacial timescales were calculated from previously developed proxy specific algorithms at ttn013 pc72 and ttn013 pc114 both located in the equatorial pacific comparison of data from the same core intervals yields conflicting results despite calibrations based on the same core top samples the periodicity of marine barite excess ba and excess al based cexport records is similar the relative magnitude of cexport when calculated using excess ba and algorithms based on sediment trap data is significantly different than records based on core top calibrations particularly during glacial intervals at both sites bulk sedimentary al ti and ba ti ratios covary however these ratios do not correspond with the downcore records of their respective excess concentrations and their accumulation rates or with contemporaneous records based on marine barite excess ba and excess al accumulation although downcore records based on sediment mass accumulation rates may be compromised by sediment focusing this process cannot explain all the differences observed among the various data sets presented here this implies that some or all of these proxies do not exclusively respond to changes in export production the contradictions among these data highlight the importance of addressing inconsistencies among paleoproxies and re examining assumptions imbedded in proxy fundamentals prior to applying paleoproductivity proxies and interpreting paleoceanographic records