seafloor geology of the monterey bay area continental shelf abstract acoustic swath mapping of the greater monterey bay area continental shelf from point ano nuevo to point sur reveals complex patterns of rock outcrops on the shelf and coarse sand bodies that occur in distinct depressions on the inner and mid shelves most of the rock outcrops are erosional cuestas of dipping tertiary rocks that make up the bedrock of the surrounding lands a mid shelf mud belt of holocene sediment buries the tertiary rocks in a continuous 6 km wide zone on the northern monterey bay shelf rock exposures occur on the inner shelf near tectonically uplifting highlands and on the outer shelf beyond the reach of the mud depositing on the mid shelf since the holocene sea level rise the sediment starved shelf off the monterey peninsula and south to point sur has a very thin cover of holocene sediment and bedrock outcrops occur across the whole shelf with salinian granite outcrops surrounding the monterey peninsula coarse sand deposits occur both bounded within low relief rippled scour depressions and in broad sheets in areas like the sur platform where fine sediment sources are limited the greatest concentrations of coarse sand deposits occur on the southern monterey bay shelf and the sur shelf

primary productivity variability on the atlantic iberian margin over the last 70 000 years evidence from coccolithophores and fossil organic compounds 1 this study analyzes coccolithophore abundance fluctuations e g emiliania huxleyi gephyrocapsa specimens and florisphaera profunda in core md01 2444 sediment strata retrieved at the iberian margin northeastern atlantic ocean coccolithophores are calcareous nannofossils a major component of the oceanic phytoplankton which provide information about past ecological and climatological variability results are supported by data on fossil organic compounds sea surface temperatures alkenones and n hexacosan 1 ol index and geochemical analyses benthic 13ccc and planktonic 18occ isotopes three scenarios are taken into account for this location at centennial scale resolution over the last 70 000 years the holocene and the stadial and interstadial modes the different alternatives are described by means of elements such as nutrients upwelling phenomena temperatures at surface and subsurface level or the arrival of surface turbid fresh and cold waters due to icebergs low sea level increased aridity and dust during the holocene moderate primary productivity was observed mainly concentrated in e huxleyi specimens surface temperatures were at maxima while the water column was highly ventilated by northern sourced polar deep waters and warmer subsurface nutrient poor subtropical waters over most of the last glacial stadials surface productivity weakened higher f profunda and reworked specimen percentages and lower diunsaturated and triunsaturated c37 alkenones the arrival of cold arctic surface waters traced by tetraunsaturated c37 peaks and large e huxleyi together with powerful ventilated southern sourced polar deep waters disturbed in all likelihood the delicate vertical equilibrium while preventing significant upwelling mixing finally during the last glacial interstadials lower f profunda percentages nonreworked material and higher diunsaturated and triunsaturated c37 alkenones a combined signal is observed warm surface temperatures were concurrent with generally low oxygenation of the deep sea floor moderate arrival of northern sourced deep waters and subsurface cold nutrient rich recently upwelled waters probably of polar origin these particular conditions may have promoted vertical mixing while enhancing surface primary productivity mainly of gephyrocapsa specimens

conflicting coccolithophore and geochemical evidence for productivity levels in the eastern mediterranean sapropel s1 abstract the cyclic development of anoxic conditions in the eastern mediterranean deep sea waters is one of the most fascinating research topics in paleoceanographic studies in combination with bottom water stagnation enhanced primary production is a common explanation for the deposition of organic rich layers sapropels this is supported by extensive evidence from both geochemical and micropaleontological studies the correspondence of recent sapropel layers with peaks of the lower photic zone coccolithophore species florisphaera profunda has been interpreted as a proxy for the development of a deep chlorophyll maximum dcm due to the pycnocline nutricline shallowing into the lower part of the photic zone we present millennial scale data for coccolithophore assemblages from sediments across the most recent sapropel s1 in the odp hole 964b drilled in the ionian sea relative and absolute abundances of taxa are compared with selected elemental composition of the bulk sediments the mn al and ba al profiles are used to determine the original thickness of the s1 interval and show that the upper part of s1 was affected by post depositional oxidation of organic matter the nannofossil accumulation rate defined by the number of coccoliths cm 2 kyr 1 suggests that there is no evidence of increased productivity within most of the sapropel layer in fact coccolithophore production was at its minimum in the lower part minimum coccolith concentrations are reached despite the increase in f profunda in both relative and absolute abundance we suggest that the dcm deduced from the increased productivity of this species did not significantly contribute to the putative overall increased primary productivity during the deposition of most of the sapropel layer within the upper oxidized part of s1 coccolith accumulation was at least five times higher than in the lower part this period of high coccolith productivity finds a counterpart in the increase of the ba al ratio the total concentration of coccoliths is again controlled by the amount of e huxleyi but it is also supported by concomitant increases in all the other groups suggesting that coccolithophore productivity increased throughout the year and through the total vertical extent of the photic zone at site 964 this is apparently the only moment when coccolithophores contributed substantially to the increased primary productivity generally assumed for the s1 layer

phyto_ and zooplankton paleofluxes during the deposition of sapropel s1 eastern mediterranean biogenic carbonate preservation and paleoecological implications abstract the relative and absolute abundances and accumulation rates of foraminifera and calcareous nannofossils were quantified in a box core containing sapropel s1 from the florence rise area se of cyprus 2302 m water depth the main objective of this study was to reconstruct in detail variations in paleoecological conditions of water masses during the deposition of this sapropel in particular we qualitatively evaluated the importance of carbonate dissolution on planktonic assemblages to better interpret the abundance profiles obtained from the two investigated taxa selective carbonate corrosion in the core is shown by 1 the decrease in shell mass weight of selected species of planktonic foraminifera 2 the decrease in accumulation rate of dissolution susceptible holococcoliths and coccolith species and 3 the absence of pteropods however the presence of other relatively dissolution susceptible coccolith species throughout all of the s1 interval suggests moderate dissolution florisphaera profunda shows a marked increase in paleofluxes within the sapropel coupled with a decrease in the accumulation rate of the upper middle photic zone coccoliths suggesting an ecological depth separation of the water column probably characterised by higher nutrient availability at depth and nutrient depleted surface waters between 10 and 6 5 kyr bp in the same interval turborotalita quinqueloba and globigerina bulloides two foraminiferal species frequently occurring during periods of high fertility increase in relative abundance the maximum increase in relative abundance of globigerinoides ruber var alba and rosea marks the climatic optimum phase and the maximum stratification in surface water that occurred at the beginning of sapropel s1 deposition when the bottom waters were anoxic an important change in foraminiferal assemblages occurs at 8 kyr bp and corresponds with a negative shift in caco 3 ba and c org contents this short interval marks the establishment of relatively less anoxic conditions in the bottom water introducing the last phase of sapropel formation after 6 5 kyr bp a progressive re establishment of normal oceanographic conditions occurred before the real end of the sapropel s1 this transition is well recorded by the reoccurrence and major accumulation rate of the mixing indicator foraminiferal species globorotalia inflata and by the gradual decrease in abundance of f profunda

rapid environmental changes in southern europe during the last glacial period oxygen isotope records from greenland ice cores1 2 indicate numerous rapid climate fluctuations during the last glacial period north atlantic marine sediment cores show comparable variability in sea surface temperature and the deposition of ice rafted debris3 4 5 in contrast very few continental records of this time period provide the temporal resolution and environmental sensitivity necessary to reveal the extent and effects of these environmental fluctuations on the continents here we present high resolution geochemical physical and pollen data from lake sediments in italy and from a mediterranean sediment core linked by a common tephrochronology our lacustrine sequence extends to the past 102 000 years many of its features correlate well with the greenland ice core records demonstrating that the closely coupled ocean atmosphere system of the northern hemisphere during the last glacial4 extended its influence at least as far as the central mediterranean region numerous vegetation changes were rapid frequently occurring in less than 200 years showing that the terrestrial biosphere participated fully in last glacial climate variability earlier than 65 000 years ago our record shows more climate fluctuations than are apparent in the greenland ice cores together the multi proxy data from the continental and marine records reveal differences in the seasonal character of climate during successive interstadials and provide a step towards determining the underlying mechanisms of the centennial millennial scale variability

a detailed comparison of the uk 37 and coccolith records over the past 290 kyears implications to the alkenone paleotemperature method the uk 37 record and the coccolithophorid remains in a sediment core from the north atlantic ocean have been compared to assess the possible influence of changes in alkenone producing coccolithophorids on the uk 37 sea surface temperature relationship we have determined three major reversals in the populations of noelaerhabdaceae gephyrocapsa and emiliania species in the central north atlantic over the last 290 kyears 245 260 170 and 40 50 kyears bp a detailed comparison of the uk 37 and coccolithophorid records revealed the absence of significant changes in the uk 37 values despite major changes in coccolithophorid assemblages the data indicate that changes in alkenone producing organisms in the past do not involve significant changes in the uk 37 temperature relationship and that the succession did not primarily depend on climatic change it also supports the fact that the uk 37 derived sst differences observed between glacial stages 2 4 6 and 8 are not related to the succession of coccolithophorid species

western mediterranean planktonic foraminifera events and millennial climatic variability during the last 70 kyr abstract detailed study of associations of planktonic foraminifera in cores md95 2043 and odp 977 located in the alboran sea mediterranean sea has allowed the identification of 29 new faunal events defined by abrupt changes in the abundances of neogloboquadrina pachyderma right and left coiling turborotalita quinqueloba globorotalia scitula globorotalia inflata globigerina bulloides and globigerinoides ruber white and pink varieties the age model for odp 977 was based on that of md95 2043 cacho et al 1999 paleoceanogr 14 698 705 on the isotopic stratigraphy and on two ams 14c measurements sea surface temperatures ssts were estimated for the last 54 kyr using the modern analog technique mat and were compared with the ssts provided by the uk 37 method the uk 37 record is very similar to the mat annual mean temperature record for the last 8 kyr however for older times alkenone derived temperatures are consistently higher than the annual mat temperatures this offset may be due to an underestimation of the sst provided by the planktonic foraminiferal method for glacial times to an overestimation of the uk 37 record or to changes in the seasonal production of alkenones most of the variability in the fauna is related to the millennial variability of heinrich and dansgaard oeschger d o events during heinrich events hes and most of the other d o stadials g bulloides t quinqueloba and g scitula increased while n pachyderma right coiling g inflata and g ruber decreased by contrast n pachyderma left coiling was only abundant in the hes the main component of the associations n pachyderma right coiling follows a general trend similar to that of sea level and 18o this species reached its highest abundance during the last glacial maximum when sea level was at a lower position the occurrence of a shallower nutricline owing to a shallowing of the interface between atlantic inflowing and mediterranean outflowing waters could have favoured the development of neogloboquadrinids in the vicinity of the strait of gibraltar

mediterranean coccolith ecobiostratigraphy since the penultimate glacial the last 145 000 years and ecobioevent traceability abstract the mediterranean sea is a miniature ocean ideal to test the response of marine ecosystems to amplified orbital and suborbital climate changes here we present coccolith data from a sardinia channel gravity core arcose c 33 analysed over the last 145 000 years with a mean resolution of about 900 years the study highlights that regional phytoplankton assemblages underwent significant modifications between the penultimate glacial and the last interglacial as well as between the last glacial and the holocene the n ratio palaeoproductivity index suggests reduced productivity levels and the development of a deep nutricline during the last interglacial and the holocene within the last glacial period many taxa exhibit abundance fluctuations that parallel oscillations in 18 o values of globigerina bulloides tests heinrich events and stadials seem to be associated with drops in primary productivity levels as already observed in the alboran sea and the sicily channel a total of 19 ecobioevents were identified in the sardinia channel sediments including abundance fluctuations of emiliania huxleyi 4 m florisphaera profunda and gephyrocapsa oceanica the comparison of events across the mediterranean sea suggests that traceability applies to the sicily channel balearic and tyrrhenian seas supporting the adoption of a common ecobiostratigraphic scheme less certain is the correlation with the alboran sea although peaks of helicosphaera carteri and syracosphaera histrica during heinrich events and stadials suggest similar nutrient dynamics in response to suborbital climatic variations in the sicily channel southern tyrrhenian and alboran seas the traceability of events within eastern mediterranean cores is strongly limited possibly due to different physico chemical properties and nutrient dynamics

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

abrupt shoaling of the nutricline in response to massive freshwater flooding at the onset of the last interglacial sapropel event a detailed assessment of the respective roles of production export and subsequent preservation of organic carbon corg in the eastern mediterranean emed sediments during the formation of sapropels remains elusive here we present new micropaleontological results for both surface samples taken at several locations in the emed and last interglacial sapropel s5 from core lc21 in the southeastern aegean sea a strong exponential anticorrelation between relative abundances of the lower photic zone coccolithophore florisphaera profunda in the surface sediments and modern concentrations of chlorophyll a chl a at the sea surface suggests that f profunda percentages can be used to track past productivity changes in the emed prior to s5 deposition an abrupt and large increase of f profunda percentages in lc21 coincided within the multidecadal resolution of the records with the marked freshening of emed surface waters this suggests a strong coupling between freshwater bound surface to intermediate water density stratification and enhanced upward advection of nutrients to the base of the photic zone fuelling a productive deep chlorophyll maximum dcm underneath a nutrient starved surface layer our findings imply that at least at the onset of sapropel formation physical and biogeochemical processes likely operated in tandem enabling high corg accumulation at the seafloor

living coccolithophores from the gulf of sirte southern mediterranean sea during the summer of 2008 the gulf of sirte is a largely unexplored area in the southernmost mediterranean sea we are presenting here 2008 sum mer data on the distribution pattern of living coccolithophores a main phytoplankton calcifying group in 105 samples from 20 stations the survey includes coastal and offshore stations enabling us to provide indications on the dynamics of phytoplankton productivity in relation to oceanographic processes the total coccosphere concentrations show higher values in the offshore stations and lower ones for coastal sites umbellosphaera tenuis emiliania huxleyi florisphaera profunda syracosphaera pulchra hol calyptrosphaera oblonga and rhabdosphaera spp dominate the assemblages the coccolithophore community shows the typical vertical zonation with k strategist taxa among others u tenuis rhabdosphaera spp and discosphaera tubifera in the upper 75 meters depth and lower photic zone taxa dominated by f profunda below the latter species shows its maximum development in the deep chlorophyll maximum layer which occurs in the up per part of the levantine intermediate water where the nutrient content is higher than in the overlying layers the mesoscale oceanographic circulation significantly affects the spatial and vertical distribution of coccolithophores with the thermocline and halocline depth shaping the vertical zonation of coccolithophore taxa and resulting in a strong lateral gradient within the gulf in the eastern sector under the influence of the gulf of sirte anticyclone the dcm is deeper and so is the occurrence of k strat egist taxa and f profunda

productivity modes in the mediterranean sea during dansgaard oeschger 20 000 70 000 yr ago oscillations abstract the study of planktonic organisms during abrupt climatic variations of the last glacial period dansgaard oeschger oscillations d o may reveal important insights on climatic oceanographic and biological interactions here we present planktic foraminifera and coccolithophore data collected at the ocean drilling program site 963 sicily channel with a mean sampling resolution of respectively 43 5 and 98 9 yr over the interval between 70 000 and 20 000 yr ago the paleoenvironmental reconstruction suggests that three different scenarios can be seen across each d o cycle 1 oligotrophic surface water and a deep thermocline for the early interstadials 2 a deep chlorophyll maximum and coccolithophore winter spring blooming in the late interstadials 3 reduced productivity together with the shallowing of the nutricline depth during stadials and heinrich events the unique mode of productivity dynamics is corroborated by comparing our paleoecological results with those published from high resolution cores in the alboran sea clearly indicating reduced trophic levels during stadials and heinrich events finally we argue that the density contrast between the atlantic water inflow and subsurface water may have affected productivity dynamics in such a large area the strong vertical density gradient may have hampered the vertical convection of the water column producing a negative effect on biological productivity especially during stadial phases

millennial climate oscillations over the course of the ice ages the climate oscillated with a period of about 20 000 to 100 000 years superimposed on these variations were millennial oscillations of 1000 to 2000 years these oscillations also occurred in the holocene which began 11 000 years ago and has been thought to be a time of a relatively stable climate as shown on p 1257 of this issue by bond et al the perspective by oppo discusses these results obtained from marine sediments and the possible mechanisms underlying these relatively rapid changes in climate

variability of the large scale general circulation of the mediterranean sea from observations and modelling a review abstract in this paper we present an overview of the most recent findings about the mediterranean sea present day circulation structure both historical observations and numerical model simulations are presented outlining the differences and agreement the model simulations are presented for both an eddy resolving and a coarse resolution numerical model and the results are intercompared the importance of the mesoscales in modifying the large scale flow field is elucidated the critical point is the discovery of the large amplitude interannual variability of the circulation and water mass structure associated with the anomalies of atmospheric forcing over the basin the seasonal variability can be strictly related to changes in heat and momentum fluxes while the interannual variability has a component which is related to the mesoscale field the latter is very intense in the algerian current region and levantine basin but different in structure in the two regions results are shown which confirm the importance of wind driving in establishing the kinetic energy of the flow field by comparing the current transport at the strait of corsica with observations in conclusion the essential characteristics of the present day circulation are associated with the atmospheric forcing and the basin topographic structure results from palaeoceanographic simulations for the last 20 000 years show that changing the atmospheric forcing can cause large changes in the circulation structure which may have affected sapropel formation

abrupt temperature changes in the western mediterranean over the past 250 000 years a continuous high resolution western mediterranean sea surface temperature sst alkenone record spanning the past 250 000 years shows that abrupt changes were more common at warming than at cooling during marine isotope stage mis 6 sst oscillated following a stadial interstadial pattern but at lower intensities and rates of change than in the dansgaard oeschger events of mis 3 some of the most prominent events occurred over miss 5 and 7 after prolonged warm periods of high stability climate during the whole period was predominantly maintained in interglacial interstadial conditions whereas the duration of stadials was much shorter

late quaternary oceanic fronts along chatham rise indicated by phytoplankton assemblages and refined calcareous nannofossil stratigraphy for the mid latitude sw pacific abstract a quantitative analysis was carried out of planktonic diatoms biogenic opal and calcareous nannofossils biogenic calcite in late quaternary sediments mis 1 6 from four cores along a n s transect east of new zealand from 39 50 s to 50 04 s across the e w trending submarine ridge the chatham rise this was done to trace movements of oceanic fronts and to improve calcareous nannofossil stratigraphy for the last 130 000 yr in the sw pacific sites odp 1123 and q 858 are below present day subtropical surface waters north of chatham rise site dsdp 594 is below present day mixed temperate subantarctic surface water south of the rise and site odp 1120 is below subantarctic surface water the more diverse and opportunistic planktonic diatoms provided marker species for subtropical surface waters alveus marina fragilariopsis doliolus rhizosolenia bergonii and azpeitia nodulifer and others for subantarctic surface waters nitzschia kerguelensis thalassiosira lentiginosa application of these tracers permits the following conclusions 1 subtropical conditions persisted north of chatham rise throughout the past 130 000 yr in spite of the cooling of surface waters during colder periods 2 during warm times mis 5 and mis 3 and in mis 1 the sporadic occurrence of subtropical species south of chatham rise indicates occasional admixture of subtropical surface waters that far south 3 subantarctic waters extended to the southern slopes of the chatham rise during mis 5b late mis 5a to early mis 4 during the warmer time intervals in early mis 3 and during latest mis 3 to early mis 2 4 subantarctic frontal conditions existed over southern chatham rise during early mis 4 and late mis 3 to early mis 2 and 5 it is probable that during cooler times mis 6 mis 5b and in mis 2 intensified particle transport from the bounty trough to the northern flank of chatham rise occurred by intensified boundary currents the larger abundance fluctuations in both microfossil groups at the sites south of chatham rise than north of chatham rise reflect northward shifts of the circumpolar subantarctic water csw and a contemporaneous disappearance of australasian subantarctic water asw implying an elevated temperature gradient between the surface water masses north and south of the chatham rise at the times of such northward shifts of csw calcareous nannofossils are less diverse than diatoms and are less specialised some calcareous nannofossil species show abundance shifts at the same time at different latitudes two of these abundance shifts can be used for correlation between subtropical and subantarctic sediments in the sw pacific 1 reversal in the relative abundance of calcidiscus leptoporus and coccolithus pelagicus associated with the mis 2 1 boundary and 2 drop in abundance of gephyrocapsa muellerae or medium sized gephyrocapsa at the mis 4 3 boundary an additional abundance shift seems to be restricted to subtropical to mixed temperate subtropical subantarctic surface waters 3 increase in abundance of g muellerae or medium sized gephyrocapsa at the beginning of mis 2 below the okareka tephra

coccolithophore export production species composition and coccolith caco3 fluxes in the ne atlantic and abstract coccolithophores were examined in two sediment traps deployed for one year april 1989 to april 1990 at approximately 1 km water depth in the subtropical ne atlantic at 34 n 21 w station nabe 34 and in the temperate ne atlantic 48 n 21 w station nabe 48 as part of the jgofs north atlantic bloom experiment nabe at both stations maximum coccolith and coccosphere fluxes were recorded during local spring bloom periods the average coccolith and coccosphere fluxes at nabe 34 were 1 12 10 9 m 2 d 1 and 4 90 10 6 m 2 d 1 respectively at this station coccoliths from 51 taxa were identified a marked seasonal change was noticed in relative abundances of emiliania huxleyi and deep photic zone species e huxleyi dominated during spring while in late autumn the coccolith assemblage was dominated by florisphaera profunda and the coccosphere assemblage by g flabellatus and algirosphaera spp emiliania huxleyi was the most abundant species in the overall coccolith and coccosphere assemblages with 69 and 64 respectively at nabe 48 the average daily fluxes were significantly lower with 3 88 10 8 coccoliths m 2 d 1 and 8 45 10 5 coccospheres m 2 d 1 and only 36 taxa were recorded in the trap samples emiliania huxleyi was the dominant species in the coccolith assemblage throughout the year with 72 and showed maximum fluxes during spring 1990 coccolithus pelagicus exhibited a distinct seasonal pattern with maximum fluxes in early june 1989 probably related to the development of a mesoscale cyclonic eddy in the vicinity of the trap site holococcolithophore fluxes were highest during maximum sea surface temperatures in summer the coccosphere assemblage was dominated by gephyrocapsa spp syracosphaera spp and e huxleyi estimated caco3 fluxes of coccoliths coccospheres and calcareous dinophytes were compared with the caco3 content in the fine m fraction the annual mass estimated caco3 flux of coccoliths and coccospheres was 5 1 g m 2 yr at nabe 34 and 2 7 g m 2 yr at nabe 48 and that of calcareous dinophytes 0 9 and 0 1 g m 2 yr respectively these summed mass estimated values contributed on average only 55 at nabe 34 and 60 at nabe 48 to the fine fraction caco3

coccolithophore export production during the 1997 1998 el nino event in santa barbara basin california the response of coccolithophore export production to non el nino and el nino conditions was monitored during a two year period 26 march 1996 3 april 1998 in the centre of the santa barbara basin 34 14 n 120 02 w california borderland during the 1997 1998 el nino the seasonal cycle of the surface water conditions was altered by the presence of a relatively warm low nutrient and low salinity water mass throughout the studied period the total mass flux is dominated by lithogenic components with terrigenous input being highest during el nino period although the annual biogenic sediment fluxes were largely dominated by silica with diatoms as the major contributor to the opal flux the coccolith flux was high during the entire studied period during winter 1998 carbonate fluxes were unusually high for this time of the year moreover a strong positive correlation between organic carbon and opal flux indicates that siliceous phytoplankton production is the most important factor controlling organic carbon flux in the santa barbara basin a positive correlation between carbonate and organic carbon fluxes existed indeed during the final phase of el nino when the correlation between organic carbon and opal fluxes is poor the sinking coccolithophore assemblage was dominated by emiliania huxleyi followed by florisphaera profunda umbilicosphaera sibogae gephyrocapsa oceanica helicosphaera carteri gephyrocapsa muellerae and calcidiscus leptoporus the intensification of el nino 1997 1998 conditions altered the typical hydrographic structure of the santa barbara basin weakening the spring upwelling as reflected by reduced diatom fluxes in contrast the coccolith flux was relatively high during el nino particularly for the tropical species g oceanica that showed a pronounced increase in its flux when the spring upwelling was reduced under el nino conditions in addition we have found that this species has a strong correlation with nitrite phosphate and iron availability in surface water

holocene millennial scale productivity variations in the sicily channel mediterranean sea 1 the calcareous nannofossil assemblages of ocean drilling program hole 963d from the central mediterranean sea have been investigated to document oceanographic changes in surface waters the studied site is located in an area sensitive to large scale atmospheric and climatic systems and to high and low latitude climate connection it is characterized by a high sedimentation rate the achieved mean sampling resolution is 70 years that allowed the sicily channel environmental changes to be examined in great detail over the last 12 ka bp we focused on the species florisphaera profunda that lives in the lower photic zone its distribution pattern shows repeated abundance fluctuations of about 10 15 such variations could be related to different primary production levels given that the study of the distribution of this species on the sicily channel seafloor demonstrates the significant correlation to productivity changes as provided by satellite imagery productivity variations were quantitatively estimated and were interpreted on the basis of the relocation of the nutricline within the photic zone led by the dynamics of the summer thermocline productivity changes were compared with oceanographic atmospheric and cosmogenic nuclide proxies the good match with holocene master records as with ice rafted detritus in the subpolar north atlantic and the near 1500 year periodicity suggest that the sicily channel environment responded to worldwide climate anomalies enhanced northern hemisphere atmospheric circulation which has been reported as one of the most important forcing mechanisms for holocene coolings in previous mediterranean studies had a remarkable impact on the water column dynamics of the sicily channel

holocene marine 14c reservoir age variability evidence from 230th dated corals in the south china sea the south china sea scs is well connected with the western pacific and influenced by the east asian monsoon we have examined temporal variations in radiocarbon marine reservoir ages r and regional marine reservoir corrections delta r of the scs during the holocene using paired measurements of ams c 14 and tims th 230 on 20 pristine corals the results show large fluctuations in both r and delta r values over the past 7500 years yrs with two distinct plateaus during 7 5 5 6 and 3 5 2 5 thousand calendar years before present cal ka bp the respective weighted mean delta r values of these plateaus are 151 85 and 89 59 yrs which are significantly higher than its modern value of 23 52 yrs this suggests that using a constant modern delta r value to calibrate c 14 dates of the scs marine samples will introduce additional errors to the calibrated ages our results provide the first database for the holocene r and delta r values of the scs for improved radiocarbon calibration of marine samples we interpret the two delta r plateaus as being related to two intervals with weakened el nino southern oscillation enso and intensified east asian summer monsoon easm this is because the c 14 content of the scs surface water is controlled by both the c 14 concentration of the pacific north equatorial current nec which is in turn influenced by enso induced upwelling along the pacific equator and vertical upwelling within the scs as a result of moisture transportation to midlatitude region to supply the easm rainfall

suborbital climate variability during marine isotopic stage 5 in the central mediterranean basin evidence from calcareous plankton record abstract new faunal and floral records from ocean drilling project hole 963a resolved at 80 year spacing provide evidence of suborbital scale climate variability in the central mediterranean sea throughout marine isotope stage mis 5 cold events in the central mediterranean sea indicated by low abundances of warm species and high abundances of cold species are also evident in a planktonic foraminifera paleoclimatic curve they have been linked to ngrip greenland ice core c events and appear correlative with similar sub millennial climate fluctuations identified in the north atlantic region and in the alboran basin westernmost mediterranean low resolution benthic and planktonic oxygen isotope fluctuations parallel trends in the surface records evidenced by planktonic assemblage fluctuations bolstering their interpretation as climate proxies climate events also occur in the mediterranean between named c events and may be coeval with additional climate events identified recently in the western subtropical atlantic hence we propose that frequent climate oscillations during mis 5 characterize both sides of the mid latitude north atlantic perhaps indicating millennial scale variations in mid latitude atmospheric patterns

the dynamics of the sicily strait a comprehensive study from observations and models abstract the dynamics of the sicily strait are investigated in a comprehensive study using recent in situ observations ocean general circulation model ogcm simulations and process model results in particular results of a very high resolution mediterranean model med16 developed in the context of the mercator project are described the circulation in the sicily strait can be described as a two layer exchange of atlantic water aw and eastern mediterranean outflow water eow the algerian current brings aw the upper layer eastwards and splits into two branches at the entrance to the sicily strait one flowing to the tyrrhenian sea the other into the sicily strait the later is composed of two streams referred to as the atlantic ionian stream ais and the atlantic tunisian current atc in winter the atc signature is more pronounced in summer the ais is associated with a number of well known semi permanent features including the intermittent northward extension of the ais called nais at the ionian shelf break which seems to be driven by the surface density contrast between waters of the sicilian and the ionian basins new intermittent patterns are shown by the med16 simulations for example an anticyclonic eddy called mca south of the malta channel and an anticyclonic gyre associated to the nais called naisa upwelling is well developed in august with temperature lower than 24 c along the western and southern coasts of sicily the seasonal transport of the aw through the strait has a maximum value 1 4 sv in winter and a minimum value at the end of summer 0 8 sv in the lower layer at the exit of the sicily strait the eow mainly composed of levantine intermediate water liw outflows into the tyrrhenian sea and veers to the right then as well known the liw flows along the northern coast of sicily before reaching the sardinia channel a new liw path from the sicily strait towards the sardinia channel is shown by the med16 model and is due to intermediate eddy shedding at the exit of the sicily strait the topography of the sill in the sicily strait plays a major role in the circulation a combination of barotropic baroclinic double kelvin waves on both side of the sill provides a mechanism for splitting the algerian current

effect of the emperor seamounts on trans oceanic propagation of the 2006 kuril island earthquake tsunami 1 the effect of tsunami wave scattering by the emperor seamounts on the propagation of the 2006 kuril island earthquake tsunami is demonstrated using the finite difference method the model results indicate that the contribution of the emperor seamounts on the maximum tsunami energy along the pacific coast of japan is found to be as much as 50 or more also analysis of the spectral evolution of observed tsunami records in japan suggests that the scattering waves from the emperor seamounts possibly dominate the wave components at periods of 4 to 17 minutes