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

about the role of westerly wind events in the possible development of an el nino in 2014 similarities between early 1997 and 2014 has prompted climate scientists to wonder if an el nino matching the 1997 el nino of the century could develop in 2014 until april 2014 the equatorial pacific exhibited positive heat content anomalies along with an eastward warm pool displacement similar to those found during the onset of strong el nino events yet in july 2014 the warm pool had retreated back to its climatological positions and equatorial temperature anomalies were much weaker than in mid 1997 dedicated oceanic simulations reveal that these weak interannual anomalies can be attributed to differences in westerly wind event wwe sequences in contrast with 1997 the lack of wwes from april to june significantly limited the growth of eastern pacific anomalies and the eastward warm pool displacement in 2014 with the absence of additional wwe activity prospects for a mature el nino in late 2014 are fading

temperature and salinity effects on alkenone ratios measured in surface sediments from the indian ocean abstract we compare alkenone unsaturation ratios measured on recent sediments from the indian ocean 20 n 45 s with modern sea oceanographic parameters for each of the core sites we estimated average seasonal cycles of sea surface temperature sst and salinity which we then weighted with the seasonal productivity cycle derived from chlorophyll satellite imagery the unsaturation index u37k ranges from 0 2 to 1 and correlates with water temperature but not with salinity theu37k versus sst relationship for indian ocean sediments u37k 0 033 sst 0 05 is similar to what has been observed for core tops from the pacific and atlantic oceans and the black sea a global compilation for core tops givesu37k 0 031 t 0 084 r 0 98 which is close to a previously reported calibration based on particulate organic matter from the water column for temperatures between 24 and 29 c however the slope seems to decrease to about 0 02u37k unit c for indian ocean core tops the ratios of total c37alkenones total c38alkenones and the slope of theu37k sst relationship are similar to those previously observed for cultures ofemiliania huxleyibut different from those previously published forgephyrocapsa oceanica eithere huxleyiis a major producer of alkenones in the indian ocean or strains ofg oceanicaliving in the northern indian ocean behave differently from the one cultured in contrast with coccolithophorid assemblages the ratios of c37alkenones to total c38alkenones lack clear geographic pattern in the indian ocean

northward and southward migrations of frontal zones during the past 40 kyr in the kuroshio oyashio transition area 1 the variation of sea surface temperature sst in the kuroshio oyashio transition area and the okhotsk sea during the last 40 kyr was estimated using long chain unsaturated alkyl ketones alkenones the temperature difference between the present and the last glacial period was about 5 6 c in the kuroshio oyashio transition area slightly larger than the 4 c previously reported moreover alkenones were not detected before 18 kyr b p in or near the okhotsk sea perhaps because of nearly year round sea ice expansion which would have prevented the growth of alkenone producers or because alkenones were less well preserved in surface sediments during the glacial period the northward and southward migrations of frontal zones were evaluated using differences in alkenone temperatures between stations located in the vicinity of the subarctic front saf subarctic boundary sab and kuroshio bifurcation front kbf all three frontal zones migrated southward during the glacial period compared with their present positions and their relative positions were different between the holocene and glacial periods in particular the distance between the saf and the sab was reduced during the glacial period compared with at present the northward and southward migration of the frontal zones may relate to both mid to low atmospheric circulation and polar atmospheric circulation

environmental change in yellow sea during the last deglaciation to the early holocene 15 000 8 000 bp abstract this study is the first reconstruction of the paleoenvironment and paleovegetation during the holocene interglacial and last deglaciation periods of the yellow sea carbon isotope and biomarker n alkane and alkenone compositions of organic carbon matter om from core 11 ys pcl14 collected from the central yellow sea recorded past changes in east asian monsoon eam climates the result shows the variability of the eam affected the sedimentary profile of total organic carbon toc the stable isotopes of bulk organic carbon 13 c org the atomic ratio of carbon and nitrogen c n ratio and biomarker content the oscillations of toc along the sediment core might be associated with the paleoceanographic conditions changes in the sea level related to the contribution of the autochthonous and allochthonous om input two climatic conditions were distinguished warm humid and cold dry based on the n alkane proxy and the observed changes in 13 c of individual n alkane 13 c alk between the holocene and last deglaciation were attributed to changes in plant distribution type a shift in vegetation type between climatic periods occurred as a result of different photosynthetic response to co 2 and temperature among c 3 and c 4 plants the most interesting new finding of this work is the fact that alkenone derived temperature changed independently with global climate change which might be related to the influence of the kuroshio current in the yellow sea the variations in the intensity of the eam could be the main mechanism accounting for the paleoenvironmental and paleoceanographic variation observed in the central yellow sea

changes in biological production in the mixed water region mwr of the northwestern north pacific during the last 27 kyr abstract piston core pc6 40 n 143 e provides the first record of biological production and alkenone sea surface temperature sst in the mixed water region mwr off sanriku japan in the northwestern north pacific over the last 27 kyr biogenic opal content was low until the early holocene and rapidly increased at 6 calendar kiloyears before present cal kyr bp low biological production in the mwr resulted from the reduced duration of the phytoplankton bloom during the glacial period 27 18 cal kyr bp and from nutrient depletion especially silica during the deglaciation 15 9 5 cal kyr bp in spite of the decreased amount of nutrients in the oyashio water biological production increased in the late holocene 6 cal kyr bp present the data revealed that nutrients supplied from deeper levels by eddies played an important role in biological production in the mwr contrary to the conventional concept that the oyashio current has controlled productivity in this region alkenone sst during the glacial period was on average 13 6 c which is close to the modern sst 14 6 c in june but this timing is not consistent with the climap results 13 4 14 3 c in august this result indicates that alkenone sst recorded not late spring but summer temperatures owing to a bloom shift caused by surface water cooling during the last glacial period alkenone sst was even lower during the deglaciation than during the lgm and reached a minimum 9 4 c at 14 0 cal kyr bp 15 n was very high during the deglaciation implying that nutrients in the euphotic zone were depleted around the core site nutrient stress probably had a physiological impact on coccolithophorids and resulted in the apparent minimum alkenone sst these findings indicate that the reconstruction of sst by alkenones can sometimes be very complex and possibly misleading

biomarker temperature estimates for modern and last glacial surface waters of the california current system between 33 and 42 n sea surface temperature sst estimates were made using data for c37 39 alkenones analyzed in modern and glacial age intervals of sediment cores collected along an east west 42 n from 125 to 132 w and a north south 41 33 n transect of the california current system ccs the prymnesiophyte biomarker results suggest that surface waters warmed significantly throughout this region since the last glacial maximum lgm but the magnitude of warming varied spatially stratigraphic profiles from four sediment cores along the north south transect indicate the warming period was confined to the glacial interglacial transition 15 10 ka with sst reaching a maximum value at 10 ka and maintaining a uniformly high value throughout the holocene comparison of estimates derived from analysis of modern and lgm sediment intervals indicates the magnitude of the sst change was minimal for locations south of about 36 n 1 2 c and increased significantly 3 5 c north of this latitude using a simple heat balance model we calculate from the latitudinal gradient in sst that southward flow in the california current system during the lgm was about 60 of that measured today at 36 n our findings support the conclusion of others based on pollen data that coastal upwelling in the region of the northeast pacific off northern california was significantly reduced or even completely shutdown during the lgm

interhemispheric appraisal of the value of alkenone indices as temperature and salinity proxies in high latitude locations alkenone sediment data from the nordic seas and north atlantic are compared to those from sikes et al 1997 for the southern ocean to evaluate further uk37 and uk37 as proxies to estimate cold temperatures 10 c and the effect of salinity and temperature in the relative abundance of 37 4 to the total abundance of c37 alkenones 37 4 uk37 and uk37 are found to be equally viable as proxies but there are significant regional differences in their cold temperature dependence the measurement of 37 4 in cores from the north atlantic region can be used to identify situations when uk37 is not a reliable paleothermometer variations in salinity are probably responsible for changes in the sedimentary record of 37 4 and a preliminary calibration has been obtained for 37 4 f salinity this new relationship should be further confirmed through field or laboratory experiments but it paves the way to derive a molecular proxy to reconstruct paleosalinity in surface waters

contrasting eastern pacific and central pacific types of enso abstract surface observations and subsurface ocean assimilation datasets are examined to contrast two distinct types of el nino southern oscillation enso in the tropical pacific an eastern pacific ep type and a central pacific cp type an analysis method combining empirical orthogonal function eof analysis and linear regression is used to separate these two types correlation and composite analyses based on the principal components of the eof were performed to examine the structure evolution and teleconnection of these two enso types the ep type of enso is found to have its sst anomaly center located in the eastern equatorial pacific attached to the coast of south america this type of enso is associated with basinwide thermocline and surface wind variations and shows a strong teleconnection with the tropical indian ocean in contrast the cp type of enso has most of its surface wind sst and subsurface anomalies confined in the central pacific and tends to onset develop and decay in situ

organic carbon isotopic composition of phytoplankton and sea surface pco2 reconstructions in the southern indian ocean during the last 50 000 yr simultaneous measurements of chlorophyll and carbon content carboxylase activities in phytoplankton isotopic composition of suspended particulate organic carbon poc and pco2 in surface sea water in the south indian ocean indicate that plankton populations have different carbon metabolisms on both sides of the subtropical convergence stc north of stc communities are dominated by mixo heterotrophic organisms while south of the stc physiological or biomass parameters are diagnostic of autotrophic phytoplankton only phytoplankton 13c values in the southern part showed a strong correlation with co2 aq in surface waters which permitted a relationship between these parameters using this empirical relationship we derive from sedimentary organic carbon soc 13c a reconstruction of the paleo pco2 in surface water of the southern indian ocean for the last 50 kyr during the glacial and deglacial periods the obtained paleo pco2 were higher than those recorded in the vostok ice core suggesting that the southern ocean was a potential source of co2 for the atmosphere these results are consistent with those of soc content and indicate that the biological pump was off during glacial times and unable to lower atmospheric co2 aq moreover these data confirm that stratification of the surface water in summer caused a reduction of gas exchange with the atmosphere during that period copyright

long chain alkenones in qinghai lake sediments abstract long chain methyl and ethyl alkenones c 37 c 40 containing two to four double bonds have been detected in sediments from qinghai lake china this is the first report of the alkenones in lake sediments deposited under a variety of salinity conditions where the lake has not encountered any marine incursions the presence of the alkenones suggests the presence of prymnesiophyceae in the lake which may have reached the lake via eolian transportation or seabirds sediment samples from the more saline areas of the lake contained higher concentrations of the more highly unsaturated compounds widespread use of these compounds as paleotemperature indicators in marine sediments introduces the possibility of extrapolating this approach to lacustrine environments if appropriate calibrations can be undertaken

long chain unsaturated ketones and esters in living algae and marine sediments abstract series of c37 c39 di and triunsaturated ketones and methyl and ethyl esters of hexatriacontadienoic acid c36 2 have been previously identified in marine sediments and the coccolithophorid emiliania huxleyi these compounds have now been found in four further species of the isochrysidales prymnesiophyta which are not known to bear coccoliths suggesting that they are more widely distributed in living algae than previously thought in addition the ketones have been recognised in sediments of eocene age ca 45 ma which greatly extends their known geological time range and increases their potential as molecular markers for algal input heptatriacontatetraen 2 one c37 4 octatriacontatetraen 3 one c38 4 methyl and ethyl esters of hexatriacontatrienoic acid c36 3 and the ethyl ester of hexatriacontatetraenoic acid c36 4 have also been identified in varying amounts in these algae by gas chromatography and computerised gas chromatography mass spectrometry

large changes in seasonal sea ice distribution and productivity in the sea of okhotsk during the deglaciations changes in the surface environment of the central sea of okhotsk were reconstructed using tex86 paleothermometry facilitated by the bit index in order to investigate paleoenvironmental changes during the glacial interglacial cycles the core top tex86 derived temperature is the same as the present day summer sea surface temperature sst suggesting that tex86 records seasonal rather than annually averaged ssts in this region the tex86 record reveals 3 c lower summer sst during glacial maxima than during interglacial periods and significant warming during the deglaciations 15 10 ka and 136 130 ka this is consistent with previous inferences of more expanded and persistent seasonal sea ice during the glacial periods than the present day and its substantial retreat during the deglaciation timing of the deglacial warming also coincided with a distinct increase in coccolithophorid productivity suggesting a causal relationship between sea surface warming and coccolithophorid blooms during the deglaciations the relationship could reflect an increase in the supply of fresh and warm water from the amur river during deglaciation which significantly impacted hydrology by facilitating sea surface stratification which in turn promoted production of coccolithophids

combined coccolith foraminiferal and biomarker reconstruction of paleoceanographic conditions over the past 120 kyr in the northern north atlantic 59 n 23 w we present data for north atlantic core biogeochemical ocean flux study bofs 16k 59 n 23 w water depth 2370 m including coccolith flora 18o planktonic foraminiferal sea surface temperatures ssts by fa20 and simmax methods and alkenone based u37k and u37k ssts a good correlation exists between the abundances of cold water coccolith species and foraminifera and a broad correlation exists between coccolith and alkenone abundances except in the holocene reworked cretaceous coccoliths at the last glacial maximum are coincident with warm deviations of the u37k signal assessment of various calibrations of u37k and u37k with paleotemperature shows the inappropriateness of a global correlation we have produced a north atlantic u37k calibration on the basis of north atlantic data alone u37k 0 026t 0 186 which produces sst data for summer season at 0 m water depth comparable to the warm season foraminiferal ssts except during the intervals 26 36 58 65 and 100 120 ka when the alkenones indicate somewhat cooler surface waters

miocene evolution of atmospheric carbon dioxide changes in pco2 or ocean circulation are generally invoked to explain warm early miocene climates and a rapid east antarctic ice sheet eais expansion in the middle miocene this study reconstructs late oligocene to late miocene pco2 from ep values based on carbon isotopic analyses of diunsaturated alkenones and planktonic foraminifera from deep sea drilling project sites 588 and 608 and ocean drilling program site 730 our results indicate that highest pco2 occurred during the latest oligocene 350 ppmv but decreased rapidly at 25 ma the early and middle miocene was characterized by low pco2 260 190 ppmv lower intervals of pco2 correspond to inferred organic carbon burial events and glacial episodes with the lowest concentrations occurring during the middle miocene there is no evidence for either high pco2 during the late early miocene climatic optimum or a sharp pco2 decrease associated with eais growth paradoxically pco2 increased following eais growth and obtained preindustrial levels by 10 ma although we emphasize an oceanographic control on miocene climate low pco2 could have primed the climate system to respond sensitively to changes in heat and vapor transport

asymmetric evolution of el nino and la nina the recharge discharge processes and role of the off equatorial sea surface height anomaly observed oceanic and atmospheric anomalies in the tropical pacific are analyzed to understand the symmetric and asymmetric characteristics between el nino and la nina evolutions it is noted that the evolutions are largely symmetric for el nino and la nina prior to and in their mature phase but become asymmetric afterwards it is further demonstrated that this asymmetry is due to the fact that on average the discharge process associated with el nino is stronger than the recharge counterpart associated with la nina the symmetric and asymmetric evolution for different phases of el nino southern oscillation enso is consistent with the associated recharge and discharge processes that are linked with the evolution of anomalous ocean surface current and gradient of sea surface height anomalies sshas it is suggested that the evolution of the meridional gradient of sshas in the central and eastern equatorial pacific is different between el nino and la nina years due to relatively different rates of the ssha changes on and off the equator during the decay of a warm event the equatorial ssha quickly switches from positive to negative meanwhile the off equator areas are occupied by positive sshas such changes on the equator and in the off equatorial regions make the concavity of the meridional ssha favorable for growth and persistence of westward surface zonal current anomaly in the equatorial pacific then for the enso phase transition during the decay of a cold event the slow decrease of the negative ssha on the equator combined with the disappearance of the negative ssha in the off equatorial regions makes the meridional concavity reverse easily and is unfavorable for the steady growth of the eastward surface zonal current anomaly and for the phase transition thus the asymmetric evolution of enso is associated with both the atmosphere and ocean anomalies on the equator and off the equator

spatial and temporal features of enso meridional scales 1 the spatial and temporal features of the el nino southern oscillation enso meridional scales are investigated using the hadley center global sea ice and sea surface temperature hadisst data for the period of 1950 2007 the results show that the meridional scales of the enso warm and cold events are asymmetric and exhibit interdecadal changes the meridional extent of the sea surface temperature anomalies ssta during la nina years is wider than that during el nino years this is because strengthened trades and thus strengthened upwelling and meridional currents during la nina events more effectively spread ssta away from the equator with the walker circulation weakening in recent decades which tends to reduce upwelling and meridional currents over the central and eastern equatorial pacific the meridional scales of both el nino and la nina events also decrease citation zhang w j li and f f jin 2009 spatial and temporal features of enso meridional scales geophys res lett 36 l15605

interhemispheric synchrony of the last deglaciation inferred from alkenone palaeothermometry the relative timings of the last deglacial warming in the southern and northern hemispheres are not well constrained but are a crucial component in understanding the mechanisms of deglaciation1 a clearer picture of the degree of interhemispheric synchrony has been obscured by a dearth of high resolution temperature records that can be tied to the absolute calendar timescale moreover the quantification of tropical temperatures during the last glacial cycle is controversial2 8 here we apply the alkenone method of sea surface temperature reconstruction9 10 to several high resolution sediment cores recovered from the tropical indian ocean between 20 n and 20 s the inferred initial sea surface temperature warming 15 000 calendar years ago at 20 s is in phase with northern hemisphere sea this study and air11 temperature changes but lags antarctic warming12 14 by several millennia this finding along with the results of recent modelling studies15 16 provides strong support for the idea that changes in the ocean s global thermohaline circulation were not the only cause of interhemispheric climate teleconnection during the last deglaciation

climatic change and its influence on human society in western japan during the holocene abstract a continuous reconstruction of quantitative paleotemperatures in the holocene was conducted by using alkenone sea surface temperature sst measurements from coastal sedimentary cores because of the strong correlation of sst with atmospheric temperature at in the coastal bay area this analysis enabled us to estimate a record of temperatures in western japan with high and low time resolution during the last 3000 and 10 000 years respectively the reconstructed ssts were validated by historical documents and records after 600 ad a long term trend of declining ssts can be attributed mainly to changes in solar radiation and sea level and to a lesser extent changes in the asian monsoon interestingly the profile was quite different from those reported from the open ocean during the last three millennia the ssts ats fluctuated by 2 1 c with a maximum in 820 ad 24 3 c 25 9 c and two minima in 760 bc 22 2 c 23 8 c and 990 ad 22 4 c 24 0 c low temperatures were also observed in 220 110 bc 560 620 ad and other periods historical documents suggest a notable cold period from the late 18th to early 19th centuries the overall mean value 23 6 c was comparable to the average value in the mid 20th century whereas the top sediments had an sst of 24 6 c which is higher than the maximum observed in the previous 3000 years although a cold climate was definitely observed in 1440 1730 ad which almost corresponded to the little ice age the medieval warm period was not identified in this study these temperature fluctuations cannot be explained by a single cause but rather by more than one external and internal driver of climate variability e g volcanic forcing ocean atmosphere interactions and solar forcing with respect to the influence of climate on human activity major shifts in social systems appeared to coincide with cold periods in western japan

reversed spatial asymmetries between el nino and la nina and their linkage to decadal enso modulation in cmip3 models abstractthis study examines preindustrial simulations from coupled model intercomparison project phase 3 cmip3 models to show that a tendency exists for el nino sea surface temperature anomalies to be located farther eastward than la nina anomalies during strong el nino southern oscillation enso events but farther westward than la nina anomalies during weak enso events such reversed spatial asymmetries are shown to force a slow change in the tropical pacific ocean mean state that in return modulates enso amplitude cmip3 models that produce strong reversed asymmetries experience cyclic modulations of enso intensity in which strong and weak events occur during opposite phases of a decadal variability mode associated with the residual effects of the reversed asymmetries it is concluded that the reversed spatial asymmetries enable an enso tropical pacific mean state interaction mechanism that gives rise to a decadal modulation of enso intensity and that at least three cmip3 models realistically simu

on the westward shift of tropical pacific climate variability since 2000 a profound westward shift in atmosphere ocean variability in the tropical pacific is observed when 2000 2017 is compared to 1979 1999 this westward displacement is associated with changes in oceanic kelvin wave activity along the equator especially a remarkable reduction in the eastern pacific 175 145 w this coincides with a weakening of low level westerly winds in this region and a westward shift of low level easterly winds in the central and eastern tropical pacific as well as decreased variability of vertical entrainment vertical diffusion in the ocean mixed layer in the eastern pacific the observed enhancement of the zonal contrast of the mean state across the tropical pacific seems to be associated with the westward shift of climate variability along the equator this systematically westward shift of the atmosphere ocean variability in the tropical pacific alters the impact of the tropical pacific on extra tropical climate

a salinity related occurrence of a novel alkenone and alkenoate in late pleistocene sediments from the japan sea abstract the novel alkenoate ethyl tetratriacontadienoate c34 2ee has been found in late quaternary sediments of the japan sea by using gas chromatography mass spectrometry gc ms it accompanied hexatriacontadien 3 one c36 2ek previously found in black sea sediments a linear relationship between c36 2ek and c34 2ee concentrations points to both compounds being derived from the same source most likely a specific haptophyte the relative abundance of c34 2ee in total alkenones and alkenoates was significantly higher during the last glacial maximum when the 18o in planktonic foraminifera was anomalously light strongly suggesting that c34 2ee is associated with low salinity environments as samples with abundant c34 2ee also possessed anomalously high u 37 k values low salinity may have an ecological or physiological influence on both the unsaturation and carbon chain length of alkenones and alkenoates

characteristics of alkenones synthesized by a bloom of emiliania huxleyi in the bering sea abstract we investigated the characteristics of the alkenones produced by a bloom of emiliania huxleyi in the eastern bering sea in 2000 alkenones were detected in surface waters between 57 n and 63 n where phosphate concentrations were low and the ammonium nitrate ratio was high the total alkenone content c37 2 c37 3 and c37 4 ranged from 22 0 to 349 g g 1 in suspended particles and from 0 109 to 1 42 g g 1 in surface sediments this suggests that a large proportion of the particulate alkenones synthesized in the surface water rapidly degraded within the water column and or at the water sediment interface of the bering shelf the change in the stable carbon isotopic composition 13c of c37 3 alkenone could not be explained only by variation in co2 aq in the surface water but also depended on the growth rate of e huxleyi the alkenone unsaturation index uk 37 was converted into an alkenone temperature with three equations prahl et al 1988 sikes et al 1997 muller et al 1998 sikes et al s 1997 equation gave the best correlation with the observed sea surface temperature sst in the eastern bering sea however some temperatures estimated by sikes et al s 1997 equation from the uk 37 varied from the observed sst possibly because of the rapidly changing rate of alkenone synthesis in the logarithmic growth stage or the low rate of alkenone synthesis when nutrients were limiting temperatures estimated from uk 37 in the surface sediments 6 8 8 2 c matched the observed sst in september 7 8 c but differed from the annual average sst of 4 to 5 c suggesting that most of the alkenone in the eastern bering sea was synthesized during limited periods for instance in september the relative amounts of c37 4 alkenone as proportions of the total alkenones referred to as c37 4 were high ranging from 18 3 to 41 4 low salinity water

widespread occurrence of distinct alkenones from group i haptophytes in freshwater lakes implications for paleotemperature and paleoenvironmental reconstructions abstract alkenones are c35 c42 polyunsaturated ketone lipids that are commonly employed to reconstruct changes in sea surface temperature however their use in coastal seas and saline lakes can be hindered by species mixing effects we recently hypothesized that freshwater lakes are immune to species mixing effects because they appear to exclusively host group i haptophyte algae which produce a distinct distribution of alkenones with a relatively consistent response of alkenone unsaturation to temperature to evaluate this hypothesis and explore the geographic extent of group i haptophytes we analyzed alkenones in sediment and suspended particulate matter samples from lakes distributed throughout the mid and high latitudes of the northern hemisphere n 30 our results indicate that group i type alkenone distributions are widespread in freshwater lakes from a range of different climates mean annual air temperature range 17 3 10 9 c mean annual precipitation range 125 1657 mm yr 1 latitude range 40 81 n and are commonly found in neutral to basic lakes ph 7 0 including volcanic lakes and lakes with mafic bedrock we show that these freshwater lakes do not feature alkenone distributions characteristic of group ii lacustrine haptophytes providing support for the hypothesis that freshwater lakes are immune to species mixing effects in lakes that underwent temporal shifts in salinity we observed mixed group i ii alkenone distributions and the alkenone contributions from each group could be quantified with the rik37 index additionally we observed significant correlations of alkenone unsaturation u 37 k with seasonal and mean annual air temperature with this expanded freshwater lakes dataset with the strongest correlation occurring during the spring transitional season u 37 k 0 029 t 0 49 r 2 0 60 p 0 0001 we present new sediment trap data from two lakes in northern alaska toolik lake 68 632 n 149 602 w lake e5 68 643 n 149 458 w that demonstrate the highest sedimentary fluxes of alkenones in the spring transitional season concurrent with the period of lake ice melt and isothermal mixing together these data provide a framework for evaluating lacustrine alkenone distributions and utilizing alkenone unsaturation as a lake temperature proxy

the alkenone temperature signal in western north atlantic surface waters abstract haptophyte algae derived long chain c 37 c 39 alkenones and alkyl alkenoates were analyzed in euphotic zone particulate matter collected over a 7 yr period at the oceanic flux program bermuda atlantic time series ofp bats site in the western sargasso sea surface water temperatures at the site range annually from 19 to 29 c alkenone concentrations ranged from 1 in summer to 100 ng l 1 following the passage of storms highest seasonal concentrations occurred during the late winter and spring under stratified conditions alkenone concentrations in the surface mixed layer 0 20 m were generally 2 to 4 times higher than in the deep fluorescent maximum 75 110 m consistent with emiliania huxleyi concentration profiles haidar and thierstein 2001 and indicated that alkenone production primarily occurs within the upper euphotic zone in this region alkenone compound distributions and the temperature calibrations of c 37 and c 38 methyl and ethyl alkenone unsaturation u 37 k u 38me k and u 38et k respectively were remarkably similar to that observed in an e huxleyi strain previously isolated from the same area conte et al 1998 providing strong evidence that e huxleyi is the predominant alkenone synthesizer and that characteristics exhibited by randomly isolated clones in culture are in many cases consistent with those of populations in the region of origin the bermuda calibration of u 37 k vs water temperature u 37 k 1 9835 0 2004t 0 0034t 2 r 2 0 95 n 91 is nonlinear and falls along the same trendline as euphotic zone particulates from warm 15 c waters of the eastern north atlantic conte and eglinton 1993 and mediterranean ternois et al 1997 the combined north atlantic temperature calibration u 37 k 1 1365 0 1257t 0 0018t 2 r 2 0 963 n 134 differs significantly from published coretop sediment calibrations rosell mele et al 1995 muller et al 1998 based on sea surface temperature maps levitus and boyer 1994 having a steeper slope at temperatures 24 c the reasons are not clearly apparent and manifest a need for detailed studies linking production patterns in surface waters with the signal arriving at the seafloor to fully understand the generation of the sedimentary signal

photosynthetic fractionation of 13c and concentrations of dissolved co2 in the central equatorial pacific during the last 255 000 years carbon isotopically based estimates of co2 levels have been generated from a record of the photosynthetic fractionation of 13c is equivalent to epsilon p in a central equatorial pacific sediment core that spans the last approximately 255 ka contents of 13c in phytoplanktonic biomass were determined by analysis of c37 alkadienones these compounds are exclusive products of prymnesiophyte algae which at present grow most abundantly at depths of 70 90 m in the central equatorial pacific a record of the isotopic composition of dissolved co2 was constructed from isotopic analyses of the planktonic foraminifera neogloboquadrina dutertrei which calcifies at 70 90 m in the same region values of epsilon p derived by comparison of the organic and inorganic delta values were transformed to yield concentrations of dissolved co2 is equivalent to c e based on a new site specific calibration of the relationship between epsilon p and c e the calibration was based on reassessment of existing epsilon p versus c e data which support a physiologically based model in which epsilon p is inversely related to c e values of pco2 the partial pressure of co2 that would be in equilibrium with the estimated concentrations of dissolved co2 were calculated using henry s law and the temperature determined from the alkenone unsaturation index u k 37 uncertainties in these values arise mainly from uncertainties about the appropriateness particularly over time of the site specific relationship between epsilon p and 1 c e these are discussed in detail and it is concluded that the observed record of epsilon p most probably reflects significant variations in delta pco2 the ocean atmosphere disequilibrium which appears to have ranged from approximately 110 microatmospheres during glacial intervals ocean atmosphere to approximately 60 microatmospheres during interglacials fluxes of co2 to the atmosphere would thus have been significantly larger during glacial intervals if this were characteristic of large areas of the equatorial pacific then greater glacial sinks for the equatorially evaded co2 must have existed elsewhere statistical analysis of air sea pco2 differences and other parameters revealed significant p 0 01 inverse correlations of delta pco2 with sea surface temperature and with the mass accumulation rate of opal the former suggests response to the strength of upwelling the latter may indicate either drawdown of co2 by siliceous phytoplankton or variation of co2 si oh 4 ratios in upwelling waters

alkenone sea surface temperatures in the japan sea over the past 36 kyr warm temperatures at the last glacial maximum the japan sea experienced bottom water anoxia at the last glacial maximum lgm since it is surrounded by four shallow straits the sill depths of which are close to or shallower than the drop in sea level 120 m that occurred then a distinctive negative d 18 o excursion of planktonic foraminifera also took place during the lgm this excursion has been interpreted from foraminiferal data as recording a drop in the paleosalinity of surface waters on the assumption of a constant low sea surface temperatures between 34 and 11 ka we present here a profile of alkenonebased sea surface temperatures alkenone ssts over the past 36 kyr our results suggest that ssts during the lgm were much higher than those previously assumed after considering the factors that might aaect estimation of alkenone ssts and comparisons of core top alkenone ssts values with values for modern seawater we conclude that the higher alkenone ssts during the lgm are reliable and reasonable these warm ssts were probably caused by radiative equilibrium associated with the development of stable water stratification in the japan sea during the lgm 2001 elsevier science ltd all rights reserved

quantitative reconstruction of temperature at a jōmon site in the incipient jōmon period in northern japan and its implications for the production of early pottery and stone arrowheads abstract the first emergence and development of pottery is an important archeological research topic climate change and associated ecological changes likely promoted the development of pottery however little is known about these environmental factors at the regional scale sedimentary core md01 2409 was collected off the coast of northern honshu japan and provided an excellent opportunity to quantitatively estimate temperature using an alkenone proxy this estimation is based upon the positive correlation between the sea surface temperature sst and the atmospheric temperature at near the core collection site the j mon began to produce the earliest pottery found in japan during this period this corresponds to a climatic anomaly that could be attributed to one of the global effects of the heinrich event i the event s origin in the northern north atlantic consequently weakened the asian monsoon because the two are linked via atmospheric circulation japan experienced its coldest summer sst of 8 7 c at of 5 2 c around 15 68 cal kyr bp these summer temperatures were approximately 7 11 c lower than they are currently 15 7 c and 16 7 c respectively the summer environment was a little colder than those experienced in the present day cities of nemuro and or nosappu in hokkaido subsistence in a terrestrial environment would have been difficult for the j mon people however marine products such as fish and shellfish would have been plentiful these conditions are consistent with the evidence that the earliest pottery was predominantly used for cooking marine and freshwater resources and increased diversification in the range of aquatic products used the bolling allerod and pre boreal warm episodes during deglaciation warmed climatic environments and enhanced marine biogenic production the maximum sst during this period is comparable to the modern sst despite its short duration of approximately a century or less even though the relationship between climate and the appearance of pottery in japan may not be direct the earliest pottery and projectile points stone arrows in the world are associated with the coldest period that homo sapiens experienced since arriving in the colder regions of the japanese archipelago

the very strong coastal el nino in 1925 in the far eastern pacific the 1925 el nino en event was the third strongest in the twentieth century according to its impacts in the far eastern pacific fep associated with severe rainfall and flooding in coastal northern peru and ecuador in february april 1925 in this study we gathered and synthesised a large diversity of in situ observations to provide a new assessment of this event from a modern perspective in contrast to the extreme 1982 1983 and 1997 1998 events this very strong coastal el nino in early 1925 was characterised by warm conditions in the fep but cool conditions elsewhere in the central pacific hydrographic and tide gauge data indicate that downwelling equatorial kelvin waves had little role in its initiation instead ship data indicate an abrupt onset of strong northerly winds across the equator and the strengthening weakening of the intertropical convergence zones itcz south north of the equator observations indicate lack of external atmospheric forcing by the panama gap jet and the south pacific anticyclone and suggest that the coupled ocean atmosphere feedback dynamics associated with the itczs northerly winds and the north south sst asymmetry in the fep lead to the enhancement of the seasonal cycle that produced this en event we propose that the cold conditions in the western central equatorial pacific through its teleconnection effects on the fep helped destabilize the itcz and enhanced the meridional ocean atmosphere feedback as well as helping produce the very strong coastal rainfall this is indicated by the nonlinear relation between the piura river record at 5 s and the sst difference between the fep and the western central equatorial pacific a stability proxy in summary there are two types of en events with very strong impacts in the fep both apparently associated with nonlinear convective feedbacks but with very different dynamics the very strong warm enso events like 1982 1983 and 1997 1998 and the very strong coastal en events like 1925

alkenone based reconstruction of late holocene surface temperature and salinity changes in lake qinghai china china the alkenone temperature proxy u k 0 37 indicates up to a 1 c change in mean annual air temperature or a 2 c change in summer lake water temperature during the late holocene oscillating warm and cold periods could be related to the 20th century warm period the little ice age the medieval warm period the dark ages cold period and the roman warm period the relative importance of c37 4 alkenone to total c37 alkenone production c37 4 fluctuated between 15 45 with higher values during warm periods suggesting that lake water was also fresher during these periods the coupled late holocene surface temperature and salinity changes suggest that asian monsoons strongly influenced the climate of the lake qinghai region citation liu z a c g henderson and y huang 2006 alkenone based reconstruction of lateholocene surface temperature and salinity changes in lake qinghai china geophys res lett 33 l09707 doi 10 1029 2006gl026151

holocene mg ca alkenones and light stable isotope measurements on the outer north iceland shelf md99 2269 a comparison with other multi proxy data and sub division of the holocene to evaluate whether proxies that record surface near surface and bottom water conditions from the north iceland shelf have similar trends and periodicities we examine holocene century scale pale

physical processes associated with the tropical atlantic sst gradient during the anomalous evolution in the southeastern ocean abstract this work is focused on the evolution of the dominant air sea coupled mode in the equatorial and southeastern tropical atlantic and the associated physical processes it is shown that in june august jja the evolution of the dominant mode is mainly dynamically driven and displays a coherent warming or cooling pattern extending from the angola coast toward the equator in the gulf of guinea for anomalies peaking in jja the warming cooling is initiated near the angola coast in march may it is suggested that sst anomalies along the coast and near the equator are physically connected the air sea interaction along the coast may be a major factor in triggering the development of sst anomalies near the equator which is intensified by local positive feedbacks that may include bjerknes and ekman processes in return the warming or cooling near the equator weaken the sst anomalies along the coast by changing the direction of anomalous wind slow westward rossby wave propagation may also play a role

alkenone temperature anomalies in the brazil malvinas confluence area caused by lateral advection of suspended particulate material alkenone temperatures derived from suspended particulate organic material which was collected in austral summer 2001 from surface waters 5 m south of the brazil malvinas confluence deviate from measured temperatures by 4 to 7 c when uk 37 ratios are converted to temperature using the muller et al 1998 calibration and up to 3 c when using the calibration of conte et al 2006 in contrast alkenone temperatures determined from particulate material sampled north of the confluence reveal close correspondence to in situ temperatures or show slightly higher values we suggest that the southern samples are biased by suspended organic detritus originating from the cold subpolar waters of the northward flowing malvinas current whereas the northern samples carry an uk 37 signal of tropical subtropical origin transported southward with the brazil current on the basis of surface ocean transport pathways and velocities simulated with the large scale geostrophic lsg ocean general circulation model we identify areas of the world ocean where alkenone temperatures are potentially biased to higher or lower values due to long particle residence times and lateral advection by surface currents

why were some la ninas followed by another la nina this paper investigates why some la nina events are followed by another la nina and some others are not we propose two preconditions that result in continuation of a la nina the first one is that la nina must be a strong event a major la nina this ensures that the reflected rossby wave signal at the eastern boundary of the pacific has a strong westward propagating cold ocean temperature anomaly over the off equatorial region the off equator cold anomaly may not be conducive to the equatorial recharge process and as a result may favor the persistence of cold ocean subsurface temperature anomaly and prevent the transition from la nina to el nino the second precondition is whether there are eastward propagating downwelling kelvin waves during the decay phase of a major la nina eastward propagating downwelling kelvin waves could lead to demise for a tendency for a follow up la nina the equatorial kelvin wave activities are associated with fluctuations of surface wind in the equatorial far western pacific the analysis suggests that both the surface wind in the equatorial far western pacific and the recharge discharge of the equatorial pacific are indicators for occurrence or no occurrence of a follow up la nina event

characteristics of alkenone distributions in suspended and sinking particles in the northwestern north pacific abstract we investigated alkenones recorded in suspended particles and a settling particle time series collected at three stations 40n 40 n 165 e knot 44 n 155 e and 50n 50 n 165 e in the northwestern north pacific from december 1997 to may 1999 emiliania huxleyi the most abundant alkenone producer in this area is present in surface to subsurface to 50 m depth waters the alkenone concentrations recorded in the suspended particles indicated that the seasonal alkenone particle distribution differed significantly interannually alkenone export fluxes at the three sediment trap stations ranged from 0 16 to 49 3 g m 2 day 1 and the maximum export flux which occurred in summer to fall july november was associated with a high organic carbon export flux the amount of alkenone produced during the maximum export season accounted for 60 80 of the total annual amount of alkenone and the alkenones accumulated in the sediment below the traps had characteristics corresponding to subsurface waters during the summer autumn season alkenone derived temperatures recorded in suspended particles corresponded to the in situ temperature within 2 c although alkenone derived temperatures corresponded approximately to the temperatures observed in the stratified subsurface waters at the three trap stations during the high export season large differences were observed during the low export winter spring period for example the alkenone derived temperatures observed at stations knot and 50n were much higher than the in situ subsurface temperatures reported in the world ocean atlas 2001 relatively large differences between alkenone derived temperatures and in situ temperatures in the subarctic might be due to 1 a low light limitation or 2 contributions of allochthonous alkenones in particulate material transported from subtropical areas within a warm core ring

enhancement of coccolithophorid blooms in the bering sea by recent environmental changes 1 since 1997 ocean color satellite images have revealed large scale blooms of the coccolithophorid emiliania huxleyi in the eastern bering sea the blooms are often sustained over several months and have caused ecosystem changes in the arctic ocean as well as in the bering sea we examined continental shelf sediment profiles of alkenone a biomarker for e huxleyi covering the past 70 years the alkenone records suggest that large e huxleyi blooms are a novel feature in the bering sea as they have occurred only since the late 1970s recent changes in alkenone content were closely related to the 1976 77 climatic regime shift in the north pacific implying that warming and freshening of bering sea waters promoted e huxleyi blooms the production rate of diatoms total valves in sediment samples the dominant primary producers in the bering sea also increased during the past several decades however the ratio of alkenone content to total diatom valves in the sediments increased as e huxleyi production increased suggesting that the increase in the e huxleyi production rate frequently exceeded the increase in the diatom production rate overall our results indicate a possible subarctic region ecosystem shift driven by climate change

freshwater impacts recorded in tetraunsaturated alkenones and alkenone sea surface temperatures from the okhotsk sea across millennial scale cycles 1 we present records of phytoplankton produced alkenones down a long piston core which reveal changes of sea surface temperature sst and sea surface salinity sss in the southwestern okhotsk sea over the past 120 ka between 20 and 60 ka b p alkenone derived temperatures typically increased by 6 c 8 c from periods corresponding within a few hundred years to stadials to those corresponding to interstadials recorded in greenland ice cores the abundance of c37 4 alkenone relative to total c37 alkenones percent c37 4 a possible proxy for salinity indicated that during most low sss was associated with high sst the warm freshwater events might be related to 1 a decline in the supply of saline water entering the okhotsk sea through the soya strait 2 strengthening of the freshwater supply from the amur river and precipitation over the okhotsk sea associated mainly with increased asian summer monsoon activity and 3 the effect of melting sea ice these findings increase our understanding of the close linkage between high and low latitudes in relation to climate change and the synchronicity of climate changes within a few centuries between the pacific and the atlantic sides of the northern hemisphere

ecological and environmental factors affecting alkenone distributions in seawater and sediments 1 the use of alkenones to estimate past sea surface temperatures has gained wide acceptance but there are still some issues that need to be resolved before alkenone proxies can be used confidently in all environmental settings a particular concern is defining what seawater temperature is recorded by the alkenone distributions preserved in sediments does it for example reflect a seasonal average or a snapshot of bloom conditions or some other combination of environmental effects this paper reviews some of the environmental and ecological factors that might affect alkenone distributions and in particular the influence of depth and seasonality on alkenone production in the water column

high resolution uk 37 temperature reconstructions in the south china sea over the past 220 kyr past sea surface temperatures sst in the northern and southern areas of the south china sea have been reconstructed for the past 220 kyr using the uk37 alkenone index the sst profiles follow the glacial interglacial pattern exhibiting differences between last glacial maximum and holocene that are 1 3 c larger than those observed at the same latitudes in the atlantic and pacific oceans in termination i both planktonic foraminiferal 18o and sst exhibit well defined bolling allerod and younger dryas events with temperature differences between both periods of 0 8 and 0 4 c in north and south respectively ssts record a constant north south difference of 1 c in the interglacials and nearly 2 5 c in the glacial stages these differences define two distinct climatic and water circulation patterns that correspond with glacial interglacial sea level oscillations which opened and closed water exchange with the tropical indo pacific ocean through the present sunda shelf

microbial degradation of the marine prymnesiophyte emiliania huxleyi under oxic and anoxic conditions as a model for early diagenesis long chain alkadienes alkenones and alkyl alkenoates to investigate the effect of bacterial diagenesis on the distributions of algal lipids the marine haptophyte emiliania huxleyi was incubated with estuarine sediment slurries under defined conditions oxic sulfate reducing and methanogenic rapid initial degradation of lipids corresponded to increased bacterial populations both of which subsequently declined under oxic conditions the algal c31 dienes were rapidly and completely degraded within 178 days extensive degradation of the characteristic c37 methyl alkenones occurred under all conditions up to 85 under oxic conditions however the u37k index remained essentially constant except for a slight increase at the longest oxic incubation time under anoxic conditions the alkyl alkenoates were preferentially degraded relative to the alkenones and changes in the aa36 index occurred these results demonstrate that lipids are part of the labile organic matter however they were generally degraded at multiple rates which slowed during incubation resulting in their partial preservation hence laboratory experiments conducted over only short periods cannot predict the preservation potential of lipid components furthermore preservation differed between sulfate reducing and methanogenic conditions so the roles of anaerobic processes need to be considered individually with regard to oxic vs anoxic preservation

on the variety of coastal el nino events we examine the connection between interannual anomalies of sea surface temperature sst in the central and far eastern equatorial pacific associated with basin scale and coastal el ninos variations of the sst anomalies in these two regions are largely coherent meaning coastal el ninos mostly occur together with the commonly studied basin scale el ninos of particular interest for this study though is the understanding of the coastal el ninos that are not accompanied by basin scale el ninos or that follow basin scale el ninos such coastal el ninos can have catastrophic societal consequences in western south america we identify seven coastal el ninos during 1979 2017 namely 1983 1987 1998 2008 2014 2015 and 2017 these coastal el ninos are driven by different mechanisms the coastal el ninos in 1983 1987 and 1998 occurred after basin scale el ninos a unique feature of such extreme basin scale el ninos like in 1982 1983 1986 1987 and 1997 1998 is an equatorially centered intertropical convergence zone during its decaying phase as a result positive sst anomalies persist and sometimes even strengthen in the eastern pacific in the subsequent boreal spring early summer leading to coastal el ninos the coastal el ninos in 2014 and 2015 on the other hand resulted from westerly wind bursts in the western pacific that forced downwelling kelvin waves and a thermocline depression in the far eastern pacific the formation of coastal el ninos in 2008 and 2017 were associated with westerly surface wind anomalies in the eastern equatorial pacific and largely driven by ocean surface heat flux anomalies these two coastal el ninos occur during the warm phase of the seasonal cycle so that warm ssts are amplified and or the warm season is extended along the west coast of south america thus there is a wide variety of the coastal el ninos in terms of evolution mechanism and timing

variability of unusual distributions of alkenones in the surface waters of the nordic seas 1 samples of filtered particulate organic matter pom were obtained during the summers of 1999 and 2000 from the surface waters of the nordic seas to monitor the spatial distribution of long chain alkenones the aim of the study was to appraise existing alkenone based climatic proxies in northern high latitudes unusually high percentages of the tetraunsaturated alkenone were measured in the polar waters of the east greenland current with c37 4 of up to 77 in 80 of sea ice cover values of percent c37 4 across the nordic seas showed a strong association with water mass type analysis of coccoliths in filters indicated that calcified emiliania huxleyi could not be discounted as the biological precursor of alkenones in all the water masses a combined data set of 69 samples of pom revealed a stronger correlation of percent c37 4 to sea surface salinity sss r2 0 72 than to sea surface temperature sst r2 0 50 values of percent c37 4 in sea surface pom were much higher than those in surficial sediments of the northern north atlantic to explain the discrepancy in sedimentary and surface water column percent c37 4 we propose that the alkenone contents in surface sediments underlying arctic and polar waters are a combination of autochthonous and allochthonous inputs of alkenones our results show that percent c37 4 can be used to reconstruct the relative extension of arctic polar water masses in the north atlantic however the results prevent confirmation of percent c37 4 as a paleo sss proxy in the nordic seas given its multivariate nature in our data set and the decoupling between its range of values in surface waters and sediments

evidence for differential degradation of alkenones under contrasting bottom water oxygen conditions implication for paleotemperature reconstruction abstract the successful reconstruction of sea surface temperatures using alkenone paleothermometry u37k has relied on the premise that there is no significant differential degradation of alkenones with different states of unsaturation during diagenetic processes to test this assumption we conducted a comparative study of contemporary sediments in oxic and anoxic bottom waters from the santa monica basin offshore california long chain alkenones were quantified and sea surface temperature were calculated using the calibrated u37k t relationship of prahl et al 1988 our results show that temperature record from the oxic sediments is higher by as much as 4 c compared to those from time equivalent anoxic sediments as a result of differential degradation of long chain unsaturated alkenones and bioturbation mixing in the oxic sediments the differential degradation of c37 3 vs c37 2 alone could account for up to 2 5 c difference between these two records this finding has significant implication in the interpretation of paleo sea surface temperature data using alkenone paleothermometry

wind stress variations and interannual sea surface temperature anomalies in the eastern equatorial pacific abstract vertical advection of temperature is the primary mechanism by which el nino southern oscillation enso time scale sea surface temperature sst anomalies are generated in the eastern equatorial pacific variations in vertical advection are mediated primarily by remote wind forced thermocline displacements which control the temperature of water upwelled to the surface however during some enso events large wind stress variations occur in the eastern pacific that in principle should affect local upwelling rates the depth of the thermocline and sst in this study the impact of these wind stress variations on the eastern equatorial pacific is addressed using multiple linear regression analysis and a linear equatorial wave model the regression analysis indicates that a zonal wind stress anomaly of 0 01 n m 2 leads to approximately a 1 c sst anomaly over the nino 3 region 5 n 5 s 90 150 w due to changes in local upwelling rates wind stress variations of this magnitude occurred in the easte

two types of el nino events cold tongue el nino and warm pool el nino abstract in this study two types of el nino events are classified based on spatial patterns of the sea surface temperature sst anomaly one is the cold tongue ct el nino which can be regarded as the conventional el nino and the other the warm pool wp el nino the ct el nino is characterized by relatively large sst anomalies in the nino 3 region 5 s 5 n 150 90 w while the wp el nino is associated with sst anomalies mostly confined to the nino 4 region 5 s 5 n 160 e 150 w in addition spatial patterns of many atmospheric and oceanic variables are also distinctively different for the two types of el nino events furthermore the difference in the transition mechanism between the two types of el nino is clearly identified that is the discharge process of the equatorial heat content associated with the wp el nino is not efficient owing to the spatial structure of sst anomaly as a result it cannot trigger a cold event it is also demonstrated that zonal advective feedback i e zonal adve

distributions of uk37 and uk37 in the surface waters and sediments of the nordic seas implications for paleoceanography in this paper we revise the application of the u and u indices as sea surface temperature sst proxies in the nordic seas in the summer of 1999 and 2000 we obtained samples of filtered particulate organic matter pom from surface waters 6 m depth of the nordic seas a number of samples were collected from polar waters with up to 80 of sea ice cover alkenones were detected in all of the major water masses of the nordic seas across a spectrum of sst values from 0 5 to 13 c and sss values from 29 6 to 35 6 psu concentrations of alkenones were similar in magnitude to those reported previously for the north atlantic and the southern ocean values of u from the new nordic seas pom data show no correlation with sst below 8 c in contrast below this temperature a linear correlation exists between u and regional sst supporting previous suggestions that overall u may be a more appropriate sst index for the region it must be noted however that u is calculated using the tetraunsaturated alkenone and the dominant control on this compound is not yet fully understood the new data highlight major differences between distributions of u and u in the water column pom and surficial sediments of the nordic seas we also examine the geographical dependence of the u versus sst relationship in the region s surficial sediments some areas are associated with unreliable sst estimates whereas in others the u versus sst relationship falls within the range of a global core top calibration it is suggested that the breakdown of the u sst relationship in some regions is due to ecological and sedimentological factors the latter relates to the extension of the habitats of alkenone producers in polar waters the former to the resuspension of sediments and laterally transported alkenone inputs this suggests that accurate alkenone derived sst estimates in the nordic seas are geographically constrained

sea surface temperature changes in the okhotsk sea and adjacent north pacific during the last glacial maximum and deglaciation abstract we estimated sea surface temperatures ssts in the western okhotsk sea during the last glacial maximum lgm and the last glacial termination from measurements of the alkenone unsaturation index u k 37 the t etra e ther inde x of tetraethers consisting of 86 carbon atoms tex 86 and tex 86 l in piston core sediments which reveal the climate response of this region to different types of forcings tex 86 l is a modification of tex 86 proposed for high latitude ocean regions the tex 86 l derived temperatures were not different from the alkenone derived temperatures from the same and nearby sediment samples during the lgm alkenone derived temperatures in the okhotsk sea were relatively warm these and similarly warm alkenone derived temperatures found at many other sites in the western north pacific may reflect a shift in the season of biomarker production from early summer and autumn to mid summer during the lgm as a result of the expansion of the season of sea ice cover empirical orthogonal function eof analysis of alkenone derived temperatures at 14 sites from the north pacific suggested substantial cooling between 20 and 14 cal kyr bp during the deglaciation at 11 of the sites including 4 sites in the okhotsk sea this dominant eof mode suggests either an overall seasonal bias in alkenone derived temperatures or potential shifts in the haptophyseae production season the second eof mode of variability indicated a deglacial warming trend punctuated by millennial scale cold events associated with reorganizations of the atlantic meridional overturning circulation the sst pattern corresponding to this eof mode is indicative of millennial scale meridional shifts of the axis of the westerly jet which may have affected heat transport across the kuroshio reconstructed temperature changes in particular in the okhotsk sea provide insight into the conditions that modulated the ventilation history of intermediate waters in the north pacific

alkenone distributions in the north atlantic and nordic sea surface waters 1 the c37 c39 alkenones were quantified in suspended particulate matter obtained from the surface waters of the north atlantic including the nordic seas over a temperature range of 4 20 c u37k values were linearly correlated to temperature over the entire range covered by our data set i e 4 20 c u37k 0 027t 0 036 r2 0 97 the compilation of water column data from the atlantic pacific and southern ocean and mediterranean sea suggests that the linear model may not be the best function for fitting u37k and in situ temperature values it also shows that suspended matter data from warm waters t 20 c are still needed to constrain the equation of the global curve high abundances of c37 4 were found in the coldest polar waters around 4 c c37 4 represented up to 35 a value that dropped to zero at temperatures above 10 c values of c37 4 were linearly correlated to temperature c37 4 3 7t 43 7 r2 0 50 and salinity c37 4 48 1s 1691 r2 0 78 further investigations from other oceanic basins are necessary to confirm these findings

global temperature calibration of the alkenone unsaturation index uk 37 in surface waters and comparison with surface sediments in this paper we compile the current surface seawater c37 alkenone unsaturation uk 37 measurements n 629 1 to 30 c temperature range to derive a global field based calibration of uk 37 with alkenone production temperature a single nonlinear global surface water calibration of uk 37 accurately predicts alkenone production temperatures over the diversity of modern day oceanic environments and alkenone synthesizing populations t 0 957 54 293 uk 37 52 894 uk 37 2 28 321 uk 37 3 r2 0 97 n 567 the mean standard error of estimation is 1 2 c with insignificant bias in estimated production temperature among the different ocean regions sampled an exception to these trends is regions characterized by strong lateral advection and extreme productivity and temperature gradients e g the brazil malvinas confluence in contrast to the surface water data the calibration of uk 37 in surface sediments with overlying annual mean sea surface temperature anno is best fit by a linear model anno 29 876 uk 37 1 334 r2 0 97 n 592 the standard error of estimation 1 1 c is similar to that of the surface water production calibration but a higher degree of bias is observed among the regional data sets the sediment calibration differs significantly from the surface water calibration uk 37 in surface sediments is consistently higher than that predicted from anno and the surface water production temperature calibration and the magnitude of the offset increases as the surface water anno decreases we apply the global production temperature calibration to the coretop uk 37 data to estimate the coretop alkenone integrated production temperature coretop ipt and compare this with the overlying annual mean sea surface temperature anno we use simple models to explore the possible causes of the deviation observed between the coretop temperature signal as estimated by uk 37 and anno our results indicate that the deviation can best be explained if seasonality in production and or thermocline production as well as differential degradation of 37 3 and 37 2 alkenones both affect the sedimentary alkenone signal

a biomarker approach for assessing marine and terrigenous inputs to the sediments of sea of okhotsk for the last 27 000 years abstract a sediment core taken from the sea of okhotsk which is located in the western north pacific rim with an extensive seasonal sea ice cover was investigated for lipid class compounds total organic carbon total nitrogen and 13 c of bulk organic matter to reconstruct changes in sedimentary regimes of marine and terrestrial organic matter over the last 27 kyrs higher molecular weight n alkanes fatty acids and fatty alcohols showed an increase in terrigenous inputs in glacial and to a greater extent in early deglacial periods the enhanced terrestrial input in the deglaciation stages has for the first time been found and never been reported in the open ocean biomarker profiles together with the coarse grain size distribution in nearby sediment cores suggested that sea ice rafting was the main transport mechanism of continental material to the okhotsk sea sediments however the ice rafting inputs have been weakened from 14 kyrs bp to the holocene probably due to a rapid reduction of the sea ice cover and continental shelf erosion profiles of c 37 alkenones phytol and brassicasterol as well as temporal variation in calcium carbonate and organic carbon contents indicated that the marine inputs were enhanced during the deglaciation the enhanced marine inputs were likely caused by an intensification of the primary production induced by a possibly increased nutrient supply from the continental shelves in early deglaciation and by the deglacial retreat of the sea ice cover at 14 kyrs bp this study demonstrates that biomarkers in the marginal marine sediments had recorded changes in the biogeochemical processes in the sea of okhotsk over the last 27 kyrs which may be significantly affected by changes in the okhotsk water exchange processes such as sea ice activity and sea ice transport of terrigenous materials

alkenones and alkenes in surface waters and sediments of the southern ocean implications for paleotemperature estimation in polar regions abstract the concentration of c37 c39 long chain alkenones and alkenes were determined in surface water and surface sediment samples from the subpolar waters of the southern ocean distributions of these compounds were similar in both sample sets indicating little differential degradation between or within compound classes the relative amounts of the tri to tetra unsaturated c37 alkenones increased with increasing temperature for temperatures below 6 c similar to the di and tri unsaturated c37 alkenones the c37 di tri and tetra unsaturated methyl alkenones are used in paleotemperature calculations via the u37k and the u37k ratios in these datasets the relative abundances of the c37 2 and the c37 3 alkenones as a proportion of the total c37 alkenones were opposite and strongly related to temperature the latter with more scatter but the abundance of the c37 4 alkenone showed no relationship with temperature the original definition of u37k includes the abundance of 37 4 in both the numerator and denominator and thus it is perhaps not surprising that there is considerable scatter in the values obtained for u37k at low temperatures of the two we suggest that u37k is the better parameter for use in paleotemperature estimations even in cold locations u37k values in the sediments fall on virtually the same regression line obtained for the water column samples of sikes and volkman 1993 indicating that their calibration is suitable for use in southern ocean sediments the comparison of water column data with sedimentary temperature estimates suggests that the alkenone distributions are dominated by contributions from the summer when the biomass of emiliania huxleyi and presumably flux to the sediment is expected to be high

millennial scale climate change and intermediate water circulation in the bering sea from 90 ka a high resolution record from iodp site u1340 1 millennial scale climate events in the north pacific are thought to be related to changes in the circulation of north pacific intermediate water which may have formed in the bering sea in the past to advance our understanding of the mechanisms that underlie millennial scale events bering sea sediment cores from the integrated ocean drilling program site u1340 were used to construct high resolution multiproxy climate records of the last 90 000 years sediment density records show millennial scale events resembling dansgaard oeschger events several of which are laminated interstadials were characterized by 3 5 c warming increased productivity driven by upwelling and reduced benthic oxygenation bering sea intermediate water also changed over longer timescales our records show the presence of intermediate water with lower salinity and higher oxygen content than modern beginning around 60 ka and persisting until the beginning of the deglaciation the bolling allerod was characterized by high productivity laminated sediments and strong denitrification signature our data support the idea that productivity derived changes in oxygenation at intermediate water source regions may have contributed to the intensification of the north pacific wide oxygen minima during the bolling allerod

el nino modoki and its possible teleconnection 1 using observed data sets mainly for the period 1979 2005 we find that anomalous warming events different from conventional el nino events occur in the central equatorial pacific this unique warming in the central equatorial pacific associated with a horseshoe pattern is flanked by a colder sea surface temperature anomaly ssta on both sides along the equator empirical orthogonal function eof analysis of monthly tropical pacific ssta shows that these events are represented by the second mode that explains 12 of the variance since a majority of such events are not part of el nino evolution the phenomenon is named as el nino modoki pseudo el nino modoki is a classical japanese word which means a similar but different thing the el nino modoki involves ocean atmosphere coupled processes which include a unique tripolar sea level pressure pattern during the evolution analogous to the southern oscillation in the case of el nino hence the total entity is named as el nino southern oscillation enso modoki the enso modoki events significantly influence the temperature and precipitation over many parts of the globe depending on the season the impacts over regions such as the far east including japan new zealand western coast of united states etc are opposite to those of the conventional enso the difference maps between the two periods of 1979 2004 and 1958 1978 for various oceanic atmospheric variables suggest that the recent weakening of equatorial easterlies related to weakened zonal sea surface temperature gradient led to more flattening of the thermocline this appears to be a cause of more frequent and persistent occurrence of the enso modoki event during recent decades

salinity control on long chain alkenone distributions in lake surface waters and sediments of the northern qinghai tibetan plateau china abstract long chain alkenones in lacustrine settings are potentially excellent biomarkers for the reconstruction of past terrestrial environmental conditions and have been found in many different types of lakes around the globe a wider range of factors influence the occurrence and distribution of alkenones in lake sediments and waters when compared to marine systems lake environmental conditions such as temperature in particular and salinity are among the key factors controlling alkenone distributions in lacustrine settings here we investigated alkenone distribution patterns in lakes of the northern qinghai tibetan plateau china and their possible relationship with environmental conditions by analyzing paired samples of suspended particulate matter in surface waters and surface sediments salinity of investigated lake waters ranges from almost 0 to 100 g l while temperature variation among the lakes is minimal effectively eliminating temperature effects on the alkenone distribution patterns observed here we show that 1 alkenone concentrations vary substantially between the lakes yet controlling mechanisms remain elusive 2 c37 c38 ratios are substantially lower in the lakes of the qaidam basin than in the lake qinghai region probably indicating different alkenone producers in the two regions and 3 large variations in c37 4 the percentage of the c37 4 alkenone determined from both surface waters and sediments are negatively correlated with salinity we suggest that the c37 4 index could be used as a salinity indicator at least on a regional scale with careful considerations of other potentially complicating factors however potential reasons for why salinity could significantly affect c37 4 values need further investigation

review of alkenone calibrations culture water column and sediments 1 i review the status of alkenone unsaturation parameters as proxies for growth temperature and the potential for pco2 estimates using the carbon isotopic composition of alkenones culture studies allow investigators to manipulate parameters that could influence the relative proportions of c37 and c38 ketones in producing organisms and to assess the possible influence of genetic variability on the calibration of unsaturation to growth temperature culture studies suggest large variability in the relation of unsaturation indices to growth temperature and hint that growth rate may play a role along with temperature in controlling unsaturation water column studies match the unsaturation index measured in particulate matter to ambient temperature providing a snapshot of unsaturation temperature relationship in comparison to culture work assemblages of regional water column data sets give more consistent relations of the unsaturation index to temperature although the argument can be made for regional rather than basin wide or global calibrations a much simpler picture emerges from analyzing a global array of core top sediments regressions show that the sedimentary unsaturation indices follow a linear trend that is best correlated to mean annual temperature in the upper 10 m of the overlying water column the regression is indistinguishable from the original prahl et al 1988 culture calibration of the u37k index to growth temperature exceptions occur at high latitudes where the effects of highly seasonal production and the possible influence of salinity may affect the unsaturation index in sediments core top analyses also fail to reveal the variability of other alkenone parameters for example the ratio of c37 to c38 ketones which have been found in culture studies much of the variance that appears in culture and water column calibrations is thus apparently removed in sediments perhaps by temporal averaging the promising paleo pco2 approach based on the isotopic composition of alkenones awaits the arrival of a significant number of core top and stratigraphic studies that will determine the extent to which physiological factors compromise the alkenone paleobarometer

holocene sea surface temperature and sea ice extent in the okhotsk and bering seas accurate prediction of future climate requires an understanding of the mechanisms of the holocene climate however the driving forces mechanisms and processes of climate change in the holocene associated with different time scales remain unclear we investigated the drivers of holocene sea surface temperature sst and sea ice extent in the north pacific ocean and the okhotsk and bering seas as inferred from sediment core records by using the alkenone unsaturation index as a biomarker of sst and abundances of sea ice related diatoms f cylindrus and f oceanica as an indicator of sea ice extent to explore controlling mechanisms in the high latitude pacific temporal changes in alkenone content suggest that alkenone production was relatively high during the middle holocene in the okhotsk sea and the western north pacific but highest in the late holocene in the eastern bering sea and the eastern north pacific the holocene variations of alkenone ssts at sites near kamchatka in the northwest pacific as well as in the western and eastern regions of the bering sea and in the eastern north pacific track the changes of holocene summer insolation at 50 n but at other sites in the western north pacific in the southern okhotsk sea and the eastern bering sea they do not in addition to insolation other atmosphere and ocean climate drivers such as sea ice distribution and changes in the position and activity of the aleutian low may have systematically influenced the timing and magnitude of warming and cooling during the holocene within the subarctic north pacific periods of high sea ice extent in both the okhotsk and bering seas may correspond to some periods of frequent or strong winter spring dust storms in the mongolian gobi desert particularly one centered at 4 3 thousand years before present kyr bp variation in storm activity in the mongolian gobi desert region may reflect changes in the strength and positions of the aleutian low and siberian high we suggest that periods of eastward displacement or increased intensity of the aleutian low correspond with times of increased extent of sea ice in the western okhotsk sea and eastern bering sea

depth ranges of alkenone production in the central pacific ocean we report analytical results of long chain c 37 c 39 alkenones in the surface sediments taken along a latitudinal transect at 175 e from 48 n to 15 s unsaturation degree of c 37 alkenones u k 37 indicated that alkenone temperature is the highest about 28 3 c in the tropical pacific and decreases toward 48 n about 10 1 c although the latitudinal trend of the alkenone temperature is generally similar to that of the observed sea surface temperature of the surface mixed layer the former exhibits markedly lower values than the latter does in the midlatitude 35 19 n on the basis of the comparisons between water column temperatures and alkenone temperatures in the surface sediments we estimated that in the midlatitudes alkenones are produced in the thermocline waters whereas in the high 48 40 n and low 10 n 2 s latitudes they are produced in the surface mixed layer this result is supported by the depth distribution of emiliania huxleyi and gephyrocapsa oceanica along a 155 w transect in the central pacific the latitudinal distribution of the alkenone production layers estimated from u k 37 is found to be consistent with that of the nitrate suggesting that the depth of alkenone production is mainly controlled by the nutrient supply from deeper waters alkenones in the sediments exhibited relatively large abundances in 43 27 n with a maximum at 30 n which may be explained by high productivity of haptophyte algae in kuroshio extension

on the connection between benguela and equatorial atlantic ninos and the role of the south atlantic anticyclone for the eastern tropical atlantic two recurring el nino like phenomena with high interannual sst anomalies have been described one centered in the equatorial region as part of the atlantic zonal mode and one off angola referred to as benguela nino both events are supposed to be generated not locally but by a relaxation of the trade winds in the western equatorial atlantic here the connection between sst variations in the two regions is investigated with observational data sets as well as ocean model simulations they are correlated to such an extent that joint events should rather be viewed as one atlantic nino an intriguing feature counterintuitive in view of the remote forcing mechanism is that sst anomalies off angola precede those in the equatorial atlantic we show this behavior to be related to the difference in thermocline depths and a different seasonality of interannual sst variability in the two regions while benguela ninos peak in austral fall due to the angola benguela front being located furthest to the south and high interannual variability in coastal kelvin wave activity warm events at the equator are phase locked to austral winter when the thermocline is shallow perturbation experiments confirm the importance of remote forcing from the equator for sst variability off angola and demonstrate the leading role of wind stress in the generation of sst anomalies in the eastern tropical atlantic these wind stress variations are shown to be linked to fluctuations in the strength of the south atlantic anticyclone a connection that might be important with respect to the predictability of atlantic ninos

atmosphere ocean mechanisms of climate anomalies in the angola tropical atlantic sector abstract interannual variations in the large scale atmospheric and oceanic fields over the tropical atlantic are studied in relation to rainfall anomalies on the angola coast departure patterns are constructed by stratification with respect to extremely dry and wet years and by correlation with rainfall in angola which is concentrated in march april the analysis suggests a causality chain of atmospheric oceanic anomalies variations of westward wind stress on the western equatorial atlantic constitute an early link in this chain the annual cycle is characterized by a relaxation of the wind stress from september november to february march anomalous seasonal relaxation of easterly wind stress over the western equatorial atlantic remotely forces the sea surface temperature sst departures in the eastern south atlantic a large relaxation being followed by positive sst departures sea surface temperature modulates the rainfall over downstream angola by controlling the atmospheric moisture and stability

long chain alkenones and alkyl alkenoates as palaeotemperature indicators their production flux and early sedimentary diagenesis in the eastern north atlantic the production and fate of long chain alkenones and alkenoates was examined with regard to their use as palaeotemperature indicators alkenoate abundances were higher than previously reported for other regions and more strongly correlated with temperature than was alkenone unsaturation u37k suggesting biogeographical variability in alkenone and alkenoate production in surface waters we define the aa36 ratio to parameterize alkenoate abundance and present an empirical temperature calibration derived from our euphotic zone samples for use in the north atlantic t 17 35 25 12 u37k 26 73 aa36 93 90 u37k aa36 significant diagenetic losses of alkenones and alkenoates were found within the water column and near surface sediments in spite of diagenetic losses the temperature signal recorded by these compounds in the sediments remains largely unaltered and corresponds to the euphotic zone water temperature during the springtime period of maximum coccolithophorid production and flux rather than the average annual sea surface temperature

alkenones alkenoates and organic matter in coastal environments of nw scotland assessment of potential application for sea level reconstruction reconstruction of late quaternary sea level history in areas of glacioisostatic uplift often relies on sediment archives from coastal isolation basins natural coastal rock depressions previously isolated from or connected to the sea at different times proxy indicators for marine brackish or lacustrine conditions combined with precise dating can constrain the time when the sea crossed the sill threshold and isolated or connected the basin the utility of isolation basins in investigations of sea level change is well known but investigations have been mostly limited to microfossil proxies the application of which can be limited by preservation and nonanalog problems here we investigate the potential of long chain alkenones alkenoates and bulk organic parameters toc corg n for reconstructing past sea level changes in isolation basins in nw scotland we analyze organic biomarkers and bulk parameters from both modern basins at different stages of isolation from the sea and fossil basins with sea level histories reconstructed from established proxies logit regression analysis was employed to find which of the biomarker metrics or bulk organic measurements could reliably characterize the sediment samples in terms of a marine brackish or isolated lacustrine origin the results suggested a good efficiency for the alkenone index c37 4 at predicting the depositional origin of the sediments this study suggests that alkenones could be used as a novel proxy for sea level change in fossil isolation basins especially when microfossil preservation is poor

high time resolution alkenone paleotemperature variations in tokyo bay during the meghalayan implications for cold climates and social unrest in japan abstract the regional paleoenvironmental record of tokyo central japan is required to enrich our understanding of climate change in east asia and its impact on japanese civilizations previous studies have generated paleotemperature records based on the analysis of shell mounds along the coast of tokyo bay and pollen from terrestrial borehole cores however a continuous high time resolution quantitative paleotemperature record does not exist a piston core was recovered from tokyo bay from which 22 mollusk shells were extracted an age model for the core determined via accelerator mass spectroscopy ams 14c dating of the shells and a scoria layer from the hoei eruption 1707 ce showed that the core contains continuous record from ca 2400 bce we analyzed the alkenone unsaturation ratios uk 37 to reconstruct the variations in the paleotemperature the temperature during the meghalayan was generally warmer than that at present exhibiting a declining trend which roughly matches the changes in the orbital forcing summer insolation and the millennial scale latitudinal shift of the subarctic front in the northeastern pacific ocean the largest cold period which occurred ca 2300 bce and had a minimum temperature of 19 5 c interrupted the warm conditions this cold period may correspond to the global cooling drying 4 2 ka bp event which marks the boundary between the northgrippian and meghalayan our results also revealed that several cold periods occurred which may have been caused by decreases in solar activity or large volcanic eruptions particularly large decadal to centennial scale cold periods were observed ca 440 bce and 100 ce during the yayoi era ca 900 bce 300 ce the coldest period after the establishment of a centralized system of government ca 300 ce present was recorded ca 1050 ce which may have been caused by the combination of a strong el nino mode and reduced solar activity these climate change events can all be linked and therefore may be the potential causes of significant periods of famine and civil war in japanese history which eventually led to major shifts in japanese social systems

decreased surface salinity in the sea of okhotsk during the last glacial period estimated from alkenones 1 studies of sediment cores from the sea of okhotsk which is characterized by seasonal sea ice have shown a large variability of sea ice indicators during the glacial interglacial cycles in this study we apply the relative abundance of the c37 4 alkenone to total c37 alkenones c37 4 as a molecular indicator of salinity and water masses to further investigate surface oceanographic condition in the sea of okhotsk in the glacial period we found a large fluctuation of c37 4 4 35 with higher values 20 35 during the last glacial period and lower values 8 during warm periods suggesting a decreased surface salinity in the glacial period the variation of c37 4 was found to be consistent with the ice rafted debris ird in the sediment core correlation coefficient r2 between c37 4 and ird 0 72 this suggests that the duration of seasonal sea ice was longer in the glacial period than today the lowered surface salinity in the glacial might also have been seriously affected by the close off of the shallow soya strait which currently transports massive volumes of saline water from the sea of japan to the sea of okhotsk

asymmetry in zonal phase propagation of enso sea surface temperature anomalies 1 it is often emphasized in the literature that the phase propagation of el nino sea surface temperature sst anomalies along the equator changed from westward to eastward after a mid to late 1970s climate regime shift in the pacific theories have been developed to explain this change of phase propagation in terms of changes in background state on which el nino events develop those theories also suggest that the direction of la nina anomaly phase propagation should have changed from westward to eastward as well however the direction of la nina sst anomaly phase propagation did not change after the mid to late 1970s instead la nina ssts continued to exhibit westward phase propagation along the equator a feature overlooked in both observational analyses and theories this paper highlights the asymmetry in zonal phase propagation between el nino and la nina sea surface temperature anomalies since 1980 and discusses the implications of that asymmetry for understanding el nino southern oscillation enso dynamics

oceanographic considerations for the application of the alkenone based paleotemperature u37k index in the gulf of california abstract alkenone concentrations were determined in sediment trap samples and surficial sediments collected from guaymas basin gulf of california to investigate the factors that control the relationship between the u37k index and sst the results from the sediment trap study reveal a positive correlation r2 0 5 between alkenone fluxes and satellite avhrr sea surface temperature sst and a strong correlation r2 0 9 between u37k and sst over an annual temperature range of 20 c although sst and u37k are tightly coupled throughout two upwelling seasons the relationship deviates from the expression developed by prahl et al 1988 at temperatures higher than 26 c the possible reasons for this deviation are varied but include the observed changes in the coccolithophore species assemblage and the evolution of the thermocline during periods of high sst the seasonal pattern of alkenone fluxes higher fluxes during warm periods observed throughout the 1996 to 1997 study period causes a bias in the annually averaged u37k record resulting in temperature estimates that are 1 c higher than the annual avhrr sst average furthermore the u37k ratios obtained from core top sediments indicate an additional 2 c warm bias in the sedimentary record that may be related to the lateral inputs of alkenones from other regions of the gulf these results highlight the importance of oceanographic processes in determining the alkenone temperature signal that is preserved in sediments after accounting for such effects u37k ratios from a box core were used to reconstruct a sst record extending back to the 18th century for the guaymas basin these results indicate a steady 2 c warming of the surface waters of the gulf from early 1700s to the 1950s followed by a rapid apparent 1 c cooling between the 1950s and the 1980s

controls on alkenone unsaturation ratios along the salinity gradient between the open ocean and the baltic sea abstract alkenone unsaturation ratios of sedimentary lipids are used as a geochemical proxy for sea surface temperatures and interest is growing in their potential as indicators of different water masses and possibly of salinity we analyzed the abundance of unsaturated c37 to c38 ketones in lipid extracts of 57 surface sediment 0 1 cm samples along a salinity gradient from 8 to 33 psu in the transition from the skagerrak to the baltic sea nw europe in addition to surface sediments we analyzed alkenones in suspended particulate matter at 13 stations over a gradient in salinity from 25 to 33 psu during a bloom of the coccolithophore emiliania huxleyi alkenones were detected in all samples suspended matter and sediment with variable contributions of the tetra unsaturated c37 alkenone compound c37 4 range from 2 to 10 of total c37 alkenone content comparing the alkenone unsaturation index u37k and c37 4 data to climatological sea surface temperature and sea surface salinity data sets revealed that sst estimated from u37k of saline end members samples from the skagerrak is in the general range of modern sst during bloom periods of haptophytes at salinities below 30 psu c37 4 increases to above 5 and the unsaturation ratios cease to be related to climatological annual or seasonal sea surface temperatures on the other hand the c37 4 appears to be inversely and significantly correlated to salinity highest c37 4 proportions in the inner baltic sea are caused by an unidentified organism but in the transition area at salinities down to 10 psu the producer apparently is e huxleyi the suspended matter data together with those from the water column support the hypothesis of changing biosynthesis of alkenones under salt stress by the coccolithophore e huxleyi but constrain the maximum of c37 4 attributable to salt stress to 10 of all c37 alkenones

surface and sub surface multi proxy reconstruction of middle to late holocene palaeoceanographic changes in disko bugt west greenland we present new surface water proxy records of meltwater production alkenone derived relative sea surface temperature diatom alkenones and sea ice diatoms changes from the disko bugt area off central west greenland we combine these new surface water reconstructions with published proxy records benthic foraminifera bottom water proxy dinocyst assemblages surface water proxy along with atmospheric temperature from greenland ice core and greenland lake records this multi proxy approach allows us to reconstruct centennial scale middle to late holocene palaeoenvironmental evolution of disko bugt and the western greenland coastal region with more detail than previously available combining surface and bottom water proxies identifies the coupling between ocean circulation west greenland current conditions the atmosphere and the greenland ice sheet centennial to millennial scale changes in the wider north atlantic region were accompanied by variations in the west greenland current wgc during periods of relatively warm wgc increased surface air temperature over western greenland led to ice sheet retreat and significant meltwater flux in contrast during periods of cold wgc atmospheric cooling resulted in glacier advances we also identify potential linkages between the palaeoceanography of the disko bugt region and key changes in the history of human occupation cooler oceanographic conditions at 3 5 ka bp support the view that the saqqaq culture left disko bugt due to deteriorating climatic conditions the cause of the disappearance of the dorset culture is unclear but the new data presented here indicate that it may be linked to a significant increase in meltwater flux which caused cold and unstable coastal conditions at ca 2 ka bp the subsequent settlement of the norse occurred at the same time as climatic amelioration during the medieval climate anomaly and their disappearance may be related to harsher conditions at the beginning of the little ice age

surface water changes recorded in late quaternary marine sediments of the ulleung basin east sea japan sea abstract in order to reconstruct past sea surface temperature sst and salinity sss in the east sea japan sea this study investigated the oxygen isotopic composition of the planktonic foraminifer globigerina bulloides and the degree of unsaturation of alkenones in bulk sediments of core ty99pc18 recovered from the southeastern part of the ulleung basin east sea between 11 and 15 cal kyr bp the surface waters were 2 4 c cooler than today the surface salinity was 12 lower during 14 15 cal kyr bp than today then increased after 14 cal kyr bp but remained lower during 11 14 cal kyr bp than present values between 14 and 15 cal kyr bp the northern east china sea surface waters were likely to be greatly diluted by fresh water discharge from land and coastal waters would have flowed into the east sea through the korea strait during 11 14 cal kyr bp the southern input waters most likely changed from fresh water influenced coastal water to open ocean water the increased salinity probably enhanced active deep water convection at that time during 7 11 cal kyr bp the surface waters were warmer 1 c and more saline 1 3 than today indicating that the warm and saline kuroshio current became stronger and that one of its branches flowed into the east sea during this time interval the cold 2 c and less saline waters 1 at 3 6 cal kyr bp may indicate a suppression of the kuroshio current the sst and sss values are close to the present values at about 3 cal kyr bp suggesting that the physiological conditions of the east sea approached that of the present at this time

impact of a coccolithophorid bloom on the co2 system in surface waters of the eastern bering sea shelf 1 a bloom of the coccolithophorid e huxleyi occurred on the eastern bering sea shelf during september october 2000 we examined the impact of this bloom on the co2 system in the surface water drawdowns of total alkalinity talk from the values predicted by the talk salinity conservative mixing relationship reached a maximum of 82 0 mol kg 1 but was confined to latitudes 57 0 n 61 0 n surface water partial pressures of co2 pco2 in excess of 400 atm depletion of nitrate nitrite and low concentrations of silicate were also found together with the talk drawdowns the relationship between salinity normalized talk and total co2 suggests that the ratio of calcification to photosynthesis during the bloom was approximately 1 0 implying that any co2 produced from calcification was balanced by photosynthesis we discuss the possible cause of the observed high surface water pco2 in the talk drawdown bloom area

distribution of the c37 tetra unsaturated alkenone in lake qinghai china a potential lake salinity indicator abstract the alkenone unsaturation index u k 37 has been applied to reconstruct past temperature changes in both marine and lacustrine systems however few studies have addressed whether the relative abundance of the c 37 4 alkenone to the total c 37 production c 37 4 can reflect surface salinity changes in lacustrine systems here we present long chain c 37 alkenone distribution patterns in surface sediments from lake qinghai china surface sediments were sampled over a large range of surface salinity changes 1 7 25 g l within lake qinghai and its surrounding lakes while temperature differences at these sampling locations should be relatively small we have found that c 37 4 varies from 15 to 49 as surface salinity decreases we tentatively describe this c 37 4 salinity link with a general linear regression c 37 4 53 4 7 8 1 73 0 45 s n 28 r 2 0 62 although step wise c 37 4 changes in response to salinity variation may exist u k 37 values vary between 0 10 and 0 16 at these sites and the inferred range of lake water temperature changes is 2 3 c suggesting that u k 37 largely reflects temperature signal across a large salinity range consistent with previous findings that u k 37 can indicate temperature changes over a large diversity of environmental settings we have also found that u k 37 values are correlated with salinity changes r 2 0 4 and thus cannot exclude potential temperature effect on c 37 4 and salinity effect on u k 37 in this study however even extreme estimates of temperature differences within the lake are still unable to explain the observed c 37 4 changes we therefore suggest that c 37 4 could be used to infer past lake salinity changes at a regional scale

contrasting the termination of moderate and extreme el nino events in coupled general circulation models as in the observed record the termination of el nino in the coupled ipcc ar4 climate models involves meridional processes tied to the seasonal cycle these meridional processes both precondition the termination of el nino events in general and lead to a peculiar termination of extreme el nino events such as those of 1982 83 and 1997 98 in which the eastern equatorial pacific warm sea surface temperature anomalies ssta persist well into boreal spring early summer the mechanisms controlling the peculiar termination of extreme el nino events which involves to the development of an equatorially centred intertropical convergence zone are consistent across the four models that exhibit extreme el ninos and observational record suggesting that this peculiar termination represents a general feature of extreme el ninos further due to their unusual termination extreme el ninos exhibit an apparent eastward propagation of their ssta which can strongly influence estimates of the apparent propagation of enso over multi decadal periods interpreting these propagation changes as evidence of changes in the underlying dynamical feedbacks behind el nino could therefore be misleading given the strong influence of a single extreme event

molecular stratigraphy a new tool for climatic assessment variations in sea surface temperatures over the past 500 000 years are inferred from the relative abundance behaviour of two organic compounds c37 alkenones over the upper 8 metres of a sediment core from the eastern equatorial atlantic this molecular record ascribed to contributions from prymnesiophyte algae correlates well with the variations in the 18 signal for the calcareous skeletons of certain planktonic foraminifera thus providing the first demonstration of a new stratigraphical technique which may be especially valuable where methods based on carbonate 18 fail

comparison of settling particles and sediments at images coring site in the northwestern north pacific effect of resuspended particles on paleorecords abstract in order to understand settling process of particles in high sedimentation area one mooring of sediment trap was deployed right above the images coring site in the northwestern north pacific in spite of two large maxima of settling particle fluxes in june july 2002 and october early january 2003 organic matter om and carbonate showed higher peaks in june july while lithogenics showed a large peak in october early january with degraded om low aspartic acid beta alanine asp bala and glutamic acid gamma aminobutyric glu gaba ratios fresh om production peaked in june july 2002 and april may 2003 thus a large export production occurred in spring early summer april june alkenone production was enhanced mainly in june july the mean alkenone sst of the settling particles was rather consistent with the observed annual mean sst and alkenone sst determined from the surface sediments on the other hand the maximum lithogenic flux along with the degradation of om indicated that a significant amount of resuspended matter contaminated the bottom sediments based upon idealized model the current and settling speeds make fractionation by size and density of resuspended particles during the settling process accumulation rates of lithogenics were 5 times those in the sediment traps which indicate large contribution of resuspended particles to settling particles especially during october early january when the tsugaru current showed high current speed these observations call our attention to carefully reconstruct paleo environments based upon lithogenics and several other proxies such as biogenic silica which would be biased for example in the record of images core at site shimokita located on the gentle continental slope

surface ocean cooling in the subarctic north pacific during the late pliocene suggests an atmospheric reorganization prior to extensive northern hemisphere glaciation abstract this paper presents records of tex 86 l and u 37 k derived sea surface temperatures ssts from ocean drilling program site 882 in the subarctic north pacific over the last 5 8 million years the tex 86 l derived sst record shows a cooling trend from 17 c at 3 6 ma to 8 c at 2 3 ma this cooling preceded the onset of extensive northern hemisphere glaciation nhg at 2 7 ma coinciding with the intensification of the east asian winter monsoon surface cooling in the north atlantic and the gradual development of nhg the results of this study suggest that the reorganization of atmospheric circulations in the northern high latitudes from 3 6 to 2 3 ma was associated with the early stage development of the ice sheets and sea ice in the arctic and subarctic regions inducing the cooling of the north atlantic and the subarctic north pacific and the intensification of the east asian winter monsoon

el nino la nina and the nonlinearity of their teleconnections the paradigm of an atmospheric system varying linearly with respect to extreme phases of the el nino southern oscillation is questioned it is argued that the global response to tropical pacific sea surface temperature forcing will be inherently nonlinear a physical basis for this intrinsic nonlinearity is the thermodynamic control on deep convection climate statistics for warm and cold events of the tropical pacific are analyzed separately for the northern winter periods during 1950 96 composite analysis of 500 mb heights reveal planetary scale teleconnection patterns as noted in earlier studies a new result is the evidence for an appreciable 358 longitude phase shift between the warm and cold event circulation composites and the two wave trains appear to have different tropical origins a large nonlinear component in north american surface climate anomalies is also found which is consistent with such a phase shift in teleconnections in the tropics rainfall anomalies also show evidence of nonlinear behavior the maximum rain anomalies along the equator are located east of the date line during warm events but west of the date line during cold events the interpretation of this behavior is complicated however by the fact that composite warm event sst anomalies are not the exact inverse of their cold event counterparts idealized atmospheric general circulation model agcm experiments are performed in order to test the question of whether the observed nonlinearity is an intrinsic property of the atmospheric system the model is forced with a composite sst anomaly that undergoes a realistic seasonally varying enso life cycle as described by e rasmusson and t carpenter both positive and negative phases of the sst anomaly are used and a 40 member ensemble of warm and cold event model simulations is conducted a nonlinear climate response in the agcm is found that closely resembles the observed composites including a shift in the equatorial positions of the maxmium rain responses and a phase shift of teleconnection patterns in the upper troposphere barotropic model experiments indicate that the inherent nonlinearity in the tropical rain response may itself be responsible for the phase shift in the extratropical teleconnection patterns

production and turnover rates of c37 alkenones in the eastern bering sea implication for the mechanism of a long duration of emiliania huxleyi bloom abstract production and turnover rates of c37 alkenones were determined by a 13c labeling technique during the emiliania huxleyi blooms in the eastern bering sea the production rates of c37 alkenones are variable in the surface water of the bering sea during emiliania huxleyi blooms ranging from 0 019 0 043 g l 1 day 1 for c37 2 and 0 057 0 16 for g l 1 day 1 c37 3 respectively the temperature difference dt between in situ temperature and uk 37 based temperature estimated by c37 alkenone unsaturation index uk 37 for seston is generally larger than the temperature difference between in situ temperature and pr uk 37 based temperature estimated by the unsaturation index of c37 alkenone production rate therefore the application of pr uk 37 determined by the 13c labeling can be suggested as a more accurate calibration of in situ temperature on the other hand the c37 alkenones concentration 3 1 g l 1 at br 10 middle shelf is 4 16 fold larger than the concentrations 0 19 0 77 g l 1 at other stations in addition the uk 37 based seawater temperature at br 10 4 0 c was much lower than the in situ temperature 7 5 c showing the largest seawater temperature difference dt this low temperature and high abundance of c37 alkenones may be the result of turbulent mixing like that caused by eddies on the continental slope area considering the existence of very low temperature and high ammonium concentration water in the water mass beneath the surface layer the uncoupling between the in situ temperature and uk 37 based seawater temperature in the middle of shelf area br 10 may indicate a link between the nutrient supply mechanism and the sustained emiliania huxleyi bloom from summer through autumn

el nino events and their relation to the southern oscillation 1925 1986 relationships among sea surface temperatures ssts at the coast of peru and offshore river discharge in northern peru and sea level pressure at darwin australia during the period 1925 1986 are investigated using time series plots frequency distributions and a simple statistical analysis it is shown that ssts undergo a larger seasonal cycle offshore than at the coast exhibit more interannual variability during the warm than the cool season are positively skewed during much of the year and exhibit greatest month to month persistence during the cool season many but not all episodes of above normal coastal ssts are accompanied by enhanced river discharge in northern peru comparison of the darwin pressure and coastal sst records during the past 60 years shows that el nino events episodes of above normal ssts along the coast of peru have occurred both in advance of and subsequent to major negative swings of the southern oscillation and associated climatic changes in the central equatorial pacific in addition el nino events and negative swings of the southern oscillation have occurred separately hence el nino and the southern oscillation are more loosely coupled than other studies would imply