vegetation and climate change fire regime shifts and volcanic disturbance in chiloe continental 43 s during the last 10 000 years abstract disentangling the roles of paleofires and explosive volcanism from climatic drivers of past vegetation change is a subject insufficiently addressed in the paleoecological literature the coastal region of the chiloe continental sector of northwestern patagonia is ideal in this regard considering its proximity to active eruptive centers and the possibility of establishing comparisons with more distal upwind sites where volcanic influence is minimal here we present a fine resolution pollen and macroscopic charcoal record from lago teo with the aim of documenting the local vegetation and climate history and assessing the role of disturbance regimes as drivers of vegetation change during the last 10 000 years the lago teo record shows a conspicuous warm dry interval between 7500 and 10 000 cal yrs bp followed by a cooling trend and increase in precipitation that has persisted until the present in agreement with previous studies in the region and interpretations of past southern westerly wind activity at multi millennial scales the presence of 26 tephras throughout the record allows examination of the relationship between explosive volcanism and vegetation change under contrasting climatic states of the holocene we found consistent statistically significant increases in tepualia stipularis after tephra deposition over the last 10 000 years in eucryphia caldcluvia between 7500 and 10 000 cal yrs bp and in hydrangea over the last 7500 years our results indicate a primary role of climate change as driver of long term vegetation change and as a modulator of vegetation responses to volcanic disturbance at multidecadal and centennial timescales

temporal variation of coda q during hualien earthquake of 1986 in eastern taiwan the may 20 1986 hualien earthquake sequence occurred on the northeastern coast of taiwan them 6 1 gs mb mainshock was followed by a large number of closely clustered aftershocks with the largest being anm 5 5 event one seismic station twd of the taiwan telemetered seismographic network is located in the surface projection of the source region and provides excellent recordings of the entire earthquake sequence these recordings plus events occurring in the same source area preceding the mainshock offer a unique opportunity to study the spatial and temporal variations of codaq in a region of active subduction a simple technique is devised that uses the envelope of the coda waveform to enable a quick determination of the codaq from drum records for recordings with a peak power at about 8 hz the following findings have been obtained 1 the ambient codaq near an active subduction region was as low as 145 2 there was no significant decrease in codaq within the period beginning one year and four months prior to the mainshock 3 there was a significant drop of codaq immediately after the mainshock this drop lasted approximately two days before returning to the ambient level 4 codaq values varied with focal depth

changes in latitudinal sea surface temperature gradients along the southern chilean margin since the last glacial abstract the comparison between different climate model simulations of water hosing experiments under glacial conditions points toward diverging responses in sea surface temperature changes sst especially in the southeast pacific sep this suggests that reconstituting the latitudinal sst gradient in the sep is a critical parameter for a better understanding of the mechanisms behind the abrupt climatic events since the last glacial period here we present high resolution records of sst using planktonic foraminiferal assemblages and alkenone temperature reconstructions and stable oxygen and carbon isotopes from three deep sea sediment cores along a latitudinal transect off the southern chilean coast this allowed us to reconstruct the variations of the latitudinal sst gradient and the subtropical front movements in the sep the sst results suggest a clear antarctic timing consistent with the bipolar seesaw control especially during the late glacial and the deglaciation our records do not suggest a complete oceanic heat transfer signal highlighting the implication of an atmospheric component in the heat transfers between the two hemispheres controlled by the latitudinal movements of the intertropical convergence zone in the atlantic and the associated weaker south pacific westerly split jet furthermore our records indicate variable conditions during the holocene and also emphasize the influence of local fresh water inputs from the patagonian ice sheet and or precipitation on the sst fresh water input estimates along the chilean margin north and south of 49 s from the onset of the deglaciation until 8 kyr cal bp

lhasa terrane in southern tibet came from australia the u pb age and hf isotope data on detrital zircons from paleozoic metasedimentary rocks in the lhasa terrane tibet defi ne a distinctive age population of ca 1170 ma with e hf t values identical to the coeval detrital zircons from western australia but those from the western qiangtang and tethyan himalaya terranes defi ne an age population of ca 950 ma with a similar e hf t range the ca 1170 ma detrital zircons in the lhasa terrane were most likely derived from the albany fraser belt in southwest australia whereas the ca 950 ma detrital zircons from both the western qiangtang and tethyan himalaya terranes might have been sourced from the high himalaya to the south such detrital zircon connections enable us to propose that the lhasa terrane is exotic to the tibetan plateau system and should no longer be considered as part of the qiangtang greater india tethyan himalaya continental margin system in the paleozoic reconstruction of the indian plate as current models show rather it should be placed at the northwestern margin of australia these results provide new constraints on the paleogeographic reconstruction and tectonic evolution of southern tibet and indicate that the lhasa terrane evolved as part of the late precambrian early paleozoic evolution as part of australia in a different paleogeographical setting than that of the qiangtang greater india tethyan himalaya system

the evolution of the patagonian ice sheet from 35 ka to the present day patice abstract we present patice a gis database of patagonian glacial geomorphology and recalibrated chronological data patice includes 58 823 landforms and 1 669 geochronological ages and extends from 38 s to 55 s in southern south america we use these data to generate new empirical reconstructions of the patagonian ice sheet pis and subsequent ice masses and ice dammed palaeolakes at 35 ka 30 ka 25 ka 20 ka 15 ka 13 ka synchronous with the antarctic cold reversal 10 ka 5 ka 0 2 ka and 2011 ad at 35 ka the pis covered of 492 6 x103 km2 had a sea level equivalent of 1 496 mm was 350 km wide and 2090 km long and was grounded on the pacific continental shelf edge outlet glacier lobes remained topographically confined and the largest generated the suites of subglacial streamlined bedforms characteristic of ice streams the pis reached its maximum extent by 33 28 ka from 38 s to 48 s and earlier around 47 ka from 48 s southwards net retreat from maximum positions began by 25 ka with ice marginal stabilisation then at 21 18 ka which was then followed by rapid irreversible deglaciation by 15 ka the pis had separated into disparate ice masses draining into large ice dammed lakes along the eastern margin which strongly influenced rates of recession glacial readvances or stabilisations occurred at least at 14 13 ka 11 ka 6 5 ka 2 1 ka and 0 5 0 2 ka we suggest that 20th century glacial recession a 1 is occurring faster than at any time documented during the holocene

full glacial late glacial palaeoclimate of the southern andes evidence from pollen beetle and glacial records palaeoecological studies carried out in the chilean lake district and chilotan archipelago 41 43 s record full glacial and late glacial pollen assemblages beginning just after 21000 and beetle assemblages after 18000 both sets extending until 10000 14c yr bp pollen records indicate that subantarctic parkland the vegetation of the early millennia of record changed after about 14000 yr bp to become open woodland and later north patagonian evergreen forest assemblages of plants and beetles responding more or less in unison to a strong rise in temperature 6 c behaved in accord at around 14000 until 13000 12500 yr bp the beetle fauna displaying a marked increase in obligate forest types during full glacial conditions 17400 16100 and 15300 and 14400 yr bp and in the late glacial interval after about 13000 yr bp however climate evidently coerced populations dissimilarly the pollen sequence showing an increase in plant taxa indicative of colder climate whereas the beetle fauna underwent little or no variation contrasting climate modes implied by plants and beetles may be attributed to differential responses to apparent low order temperature changes 2 3 c

abrupt vegetation changes during the last glacial to holocene transition in mid latitude south america a pollen record from the huelmo site ca 41 30 s shows that vegetation and climate changed at millennial time scales during the last glacial to holocene transition in the mid latitude region of western south america the record shows that a nothofagus parkland dominated the landscape between 16 400 and 14 600 14c yr bp along with magellanic moorland and cupressaceous conifers evergreen north patagonian rainforest taxa expanded in pulses at 14 200 and 13 000 14c yr bp following a prominent rise in nothofagus at 14 600 14c yr bp highly diverse closed canopy rainforests dominated the lowlands between 13 000 and 12 500 14c yr bp followed by the expansion of cold resistant podocarps and nothofagus at ca 12 500 and 11 500 14c yr bp local disturbance by fire favoured the expansion of shade intolerant opportunistic taxa between 10 900 and 10 200 14c yr bp subsequent warming pulses at 10 200 and 9100 14c yr bp led to the expansion of thermophilous summer drought resistant valdivian rainforest trees until 6900 14c yr bp our results suggest that cold and hyperhumid conditions characterised the final phase of the last glacial maximum lgm between 16 400 and 14 600 14c yr bp the last ice age termination commenced with a prominent warming event that led to a rapid expansion of north patagonian trees and the abrupt withdrawal of andean ice lobes from their lgm positon at ca 147 000 14c yr bp hyperhumid conditions prevailed between 16 400 and 13 000 14c yr bp what we term the extreme glacial mode of westerly activity this condition was brought about by a northward shift and or intensification of the southern westerlies the warmest driest conditions of the last glacial interglacial transition occurred between 9100 and 6900 14c yr bp during this period the westerlies shifted to an extreme interglacial mode of activity via a poleward migration of stormtracks our results indicate that a highly variable climatic interval lasting 5500 14c years separate the opposite extremes of vegetation and climate during the last glacial interglacial cycle i e the end of the lgm and the onset of the early holocene warm and dry period copyright 2003 john wiley sons ltd

chironomid and pollen evidence for climate fluctuations during the last glacial termination in nw patagonia abstract we present chironomid and pollen records from the huelmo site 41 30 s nw patagonia to examine in detail the timing and structure of climate changes during the last glacial termination in the southern mid latitudes the chironomid record has the highest temporal and taxonomic resolution for this critical interval and constitutes the first account of midge faunas at the culmination of the last glacial maximum lgm for the region the chironomid record suggests cold and wet conditions during the lgm followed by deglacial warming between 17 6 and 16 8 cal kyr bp relatively warm conditions prevailed between 15 14 cal kyr bp followed by a reversal in trend with cooling pulses at 14 and 13 5 cal kyr bp and warming at the beginning of the holocene cool temperate conditions prevailed during the huelmo mascardi cold reversal hmcr which according to chironomid data exhibits a wet phase 13 5 12 8 cal kyr bp followed by a conspicuous drier phase 12 8 11 5 cal kyr bp the chironomid and pollen records from the huelmo site indicate step wise deglacial warming beginning at 17 6 cal kyr bp in agreement with other paleoclimate records from nw patagonia and isotopic signals from antarctic ice cores peak warmth during the last glacial termination was achieved by 14 5 cal kyr bp followed by a cooling trend that commenced during the antarctic cold reversal which later intensified and persisted during the hmcr 13 5 11 5 cal kyr bp we observe a shift toward drier conditions at 12 8 cal kyr bp superimposed upon the hmcr coeval with intense fire activity and vegetation disturbance during younger dryas time

in situ cosmogenic 10be production rate at lago argentino patagonia implications for late glacial climate chronology abstract when calculated with the commonly accepted average northern hemisphere production rate 10 be dates of surface boulders on moraines in the lago argentino area of patagonia are younger than minimum limiting 14 c ages for the same landforms this disagreement could result from the lack of a regional 10 be production rate calibration site to assess this possibility we here present high precision measurements of 10 be in samples collected from surface boulders on the herminita and puerto bandera moraine complexes deposited alongside lago argentino on the eastern flank of the andes at 50 s in patagonia together with maximum and minimum limiting 14 c ages for the two moraine systems these measurements confine the local 10 be production rate to between 3 60 and 3 82 atoms g yr midpoint 3 71 0 11 atoms g yr when using a time dependent scaling method that incorporates a high resolution geomagnetic model this range includes upper and lower error bounds of acceptable production rates derived from both the herminita and the puerto bandera sites the upper limit of this range is more than 12 below the average northern hemisphere production rate as calculated using the same scaling method given in balco et al quat geochron 3 2008 174 195 other scaling models yield production rates with similarly large offsets from the balco et al 2008 rate on the other hand the range of acceptable production rate values determined from patagonia overlaps at 1 with and encompasses the production rate recently derived in macaulay valley in the southern alps of new zealand a putnam et al quat geochron 5 2010a 392 409 within uncertainties i e overlap at 1 sigma this patagonian production rate range also agrees with a recently determined production rate from low elevation sites in northeastern north america and northern norway when the macaulay production rate is used to calculate patagonian exposure dates 14 c and 10 be chronologies are mutually compatible for late glacial moraine systems both chronologies then indicate that outlet glaciers of the southern patagonian icefield achieved a late glacial maximum in the western reaches of lago argentino at 13 000 cal yr bp at the end of the antarctic cold reversal 14 500 12 900 cal yr bp outlet glaciers subsequently receded to near present day ice margins during the younger dryas stadial 12 900 11 700 cal yr bp this general retreat was interrupted about 12 200 cal yr bp when upsala glacier constructed an interlobate complex of moraine ridges on herminita peninsula mountain glaciers in patagonia and new zealand on both sides of the south pacific ocean exhibited a coherent pattern of late glacial ice margin fluctuations

mw estimation from crustal coda waves recorded on analog seismograms abstract accurate magnitude determinations are important issues when producing seismicity catalogs aimed at assessing seismic hazard especially in moderate seismicity regions when only a few seismic stations are available the stability of coda wave amplitudes presents great advantages as compared to s lg wave amplitudes for estimating magnitude we develop a method for processing coda waves to determine the moment magnitude m w that is valid both for recent digital short period records and old analog short period seismograms because spectral analyses of paper records are most often not possible we fit the coda envelopes of the raw time signal our empirical representation of the coda envelope is tested with synthetics and its parameters are determined using 109 earthquakes digitally recorded at 12 stations of the laboratoire de detection et de geophysique ldg french velocimetric network between 1997 and 2013 the coda parameters are adapted to the four broad geological zones that can be defined in france within each zone this model matches the observed coda wave envelope for m w between 3 4 and 5 3 synthetic coda signals computed from the regional quality factors q c f within the 0 3 7 hz frequency band of the instrument show that the frequency and regional variation of q c are enough to explain the coda shape of the raw signal this empirical coda model is only valid for events with corner frequency larger than the 1 hz cutoff frequency of the ldg instrument when applying this raw signal envelope model to actual data the site effect at each station must be accounted for from this empirical coda model we obtain stable corrected coda amplitudes that can be directly converted into m w by linear regression

lg coda q variation across eurasia and its relation to crustal evolution an extensive set of broadband and short period seismograms from regional seismic events has been used to derive a tomographic image of broad scale variations of lg coda q for most of eurasia the image indicates that lg coda q at a frequency of 1 hz varies between about 200 and 1000 lowest q values 800 are found in four regions the east european shield the siberian shield the indian shield and the southwestern and oldest portion of the altaid belt the pattern of lg coda q variation across eurasia suggests that crustal q in any region is directly proportional to the length of time that has elapsed since the most recent episode of large scale compressional tectonic activity or upper mantle heating that occurred there we interpret the low q as resulting largely from hydrothermal fluids generated by tectonic activity or heating that now reside in cracks and permeable portions of the eurasian crust crustal q increases with time after that activity as fluids are lost to the surface or absorbed by retrograde metamorphism

late quaternary vegetation of southern isla grande de chiloe chile late glacial holocene forest history of southern isla chiloe latitude 43 10 s was reconstructed on the basis of pollen analysis in three profiles laguna soledad laguna chaiguata puerto carmen prior to 12 500 yr b p pollen records are dominated by plant taxa characteristic of open habitats zone i from 12 500 yr b p to the present tree species predominate in the pollen records zones ii v between 12 500 and 9500 yr b p ombrophyllous taxa nothofagus podocarpus nubigena myrtaceae fitzroya pilgerodendron and drimys are frequent in all pollen diagrams suggesting a wetter and colder climate than the present between 9000 and 5500 yr b p valdivian forest elements such as nothofagus dombeyi type weinmannia and eucryphia caldcluvia dominate indicating a period of drier and warmer climate from 5500 yr b p onward the expansion of mixed north patagonian subantarctic forest elements and the increased frequence of tepualia suggest increased rainfall and temperatures oscillating around the modern values the change from open to forest vegetation ca 12 500 yr b p probably represents the most pronounced climatic change in the record and can be interpreted as the glacial postglacial transition in the study area

high resolution marine record of climatic change in mid latitude chile during the last 28 000 years based on terrigenous sediment parameters abstract marine sediment cores from the continental slope off mid latitude chile 33 s were studied with regard to grain size distributions and clay mineral composition the data provide a 28 000 yr14c accelerator mass spectrometry dated record of variations in the terrigenous sediment supply reflecting modifications of weathering conditions and sediment source areas in the continental hinterland these variations can be interpreted in terms of the paleoclimatic evolution of mid latitude chile and are compared to existing terrestrial records glacial climates 28 000 18 000 cal yr b p were generally cold humid with a cold semiarid interval between 26 000 and 22 000 cal yr b p the deglaciation was characterized by a trend toward more arid conditions during the middle holocene 8000 4000 cal yr b p comparatively stable climatic conditions prevailed with increased aridity in the coastal range the late holocene 4000 0 cal yr b p was marked by more variable paleoclimates with generally more humid conditions variations of rainfall in mid latitude chile are most likely controlled by shifts of the latitudinal position of the southern westerlies compared to the holocene the southern westerly wind belt was located significantly farther north during the last glacial maximum less important variations of the latitudinal position of the southern westerlies also occurred on shorter time scales

an assessment and calibration of formulations for bagnold s bedload equation abstract bagnold s bedload equation in the form q u ucr 3 has frequently been employed to predict sediment mass transport rates in tidal flows and to assist with the interpretation of ancient tidal deposits however physical considerations suggest that the form q u2 u2cr u is more correct this latter formulation is therefore calibrated with experimental data and the coefficient of proportionality is shown to be strongly dependent on the sediment grain size

climatic controls of holocene fire patterns in southern south america holocene fire climate vegetation linkages are mostly understood at individual sites by comparing charcoal and pollen records with other paleoenvironmental proxy and model simulations this scale of reconstruction often obscures detection of large scale patterns in past fire activity that are related to changes in regional climate and vegetation a network of 31 charcoal records from southern south america was examined to assess fire history along a transect from subtropic to subantarctic biomes the charcoal data indicate that fire activity was greater than present at ca 12 000 cal yr bp and increased further and was widespread at 9500 cal yr bp fire activity decreased and became more spatially variable by 6000 cal yr bp and this trend continued to present atmospheric circulation anomalies during recent high fire years show a southward shift in westerlies and paleoclimate model simulations and data syntheses suggest that such conditions may have prevailed for millennia in the early holocene when the pole to equator temperature gradients were weaker and annual temperatures were higher than present in response to orbital time scale insolation changes

climatic and disturbance influences on the temperate rainforests of northwestern patagonia 40 s since 14 500 cal yr bp abstract we present a detailed record from lago pichilafquen to unravel the vegetation climate and disturbance history of the lowlands of northwestern patagonia 40 s since 14 500 cal yr bp the presence of 30 tephras throughout the record attest for the proximity of the site to active volcanic centres and allows assessment of the role of volcanic disturbance on past vegetation and fire regime shifts we interpret alternations in dominance between north patagonian and valdivian rainforests driven by changes in temperature and precipitation of westerly origin at multi millennial and millennial timescales these trends were punctuated by centennial scale changes most of which were coeval with or immediately followed the deposition of tephras and or paleofires we identify departures of the local vegetation from the regional trend between 2400 and 7100 cal yr bp which we interpret as a response of rainforest vegetation and local fire regimes to the disturbance effect of tephra deposition near lago pichilafquen we also find that volcanic disturbance promoted consistent increases in eucryphia caldcluvia within 30 years and paleofires between 60 and 120 years following tephra deposition comparisons with palynological records having similar span time resolution and age control suggest that regional climate has played a central role on the establishment composition and maintenance of temperate rainforests this influence is overprinted by disturbance regimes at the local and landscape level driving divergences and heterogeneity especially at times of relatively weak climatic forcing

reconciling the onset of deglaciation in the upper rangitata valley southern alps new zealand abstract enquiry into the detailed timing of paleoclimate events depends on well resolved and reliable chronologies a recently published set of 10be surface exposure ages for moraine boulders in the upper rangitata valley was interpreted to indicate a gradual reduction in glacier surface height between c 21 and c 17 ka without rapid glacier recession beginning c 18 ka as reported from other valleys the dating results were suggested to be consistent with moraine geomorphology and an interpreted lack of post glacial lake formation in the valley in contrast we argue that the geomorphology is consistent with sustained glacier recession and we highlight evidence for a post glacial lake furthermore the upper rangitata moraine chronology was encumbered by inaccurate altitude values assigned to many of the sample sites recalculation of the 10be ages using accurate elevations produces values that are as much as 3000 years younger than originally reported the recalculated values indicate no significant age difference across the c 300 m relative altitudinal spread of sample locations with mean age of all samples c 17 7 0 3 ka the previous inference of slow late glacial ice retreat is not supported by the recalculated chronology rather the revised glacial chronology implies that substantial ice surface lowering of the last glacial maximum rangitata glacier was in progress shortly after c 18 ka the revised upper rangitata chronology is compatible with dating from other eastern valleys of the southern alps indicating moraine formation at c 18 ka followed by sustained glacier recession associated with regional climatic amelioration

site amplification factors in central and southern california determined from coda waves abstract site amplification factors at frequencies of 1 5 3 6 and 12 hz were determined for 158 stations of the southern california seismic network scsn from coda waves of 306 local earthquakes using a recursive stochastic inverse method our results for southern california are consistent with those of central california obtained by su et al 1992 in that the site amplification at a station is systematically related to the surface geology of the station site the site amplification is high for young quaternary sediments and decreases with increasing geologic age at all frequencies between 1 5 and 12 hz this decreasing rate is higher for younger rock sites gradually becomes lower with increasing geologic age and appears to be insignificant when the site reaches mesozoic age or older the relationship between site amplification and geologic age obtained for southern california agrees with that for central california amplification factors at 158 sites in southern california were combined with those at 132 sites in central california through a common reference site the result is a unique data base of site specific uniformly referenced amplification factors throughout central and southern california

temporal and spatial variation on coda q 1 associated with the north palm springs earthquake of july 8 1986 a temporal and spatial change of codaq 1 associated with the occurrence of the north palm springs earthquake of july 8 1986 was studied by using 242 small local earthquakes in the vicinity of the mainshock we found that the codaq 1 of earthquakes which occurred before the mainshock was significantly higher than that of the aftershocks in the mainshock area while the codaq 1 for the surrounding area remained almost constant throughout 1986 codaq 1 was determined separately for the lapse time windows of 10 to 20 sec and 15 to 40 sec for the period from 1981 to 1987 the result for the time window 10 to 20 sec showed a peak in codaq 1 before the time of mainshock at all frequencies the peak appeared earlier at lower frequencies there was no significant change in codaq 1 for the time window 15 to 40 sec probably because the change was restricted to a small area

lapse time dependence of coda q in the source region of the 1999 chamoli earthquake abstract in the present study the attenuation of seismic wave energy in and around the source area of the chamoli earthquake of 29 march 1999 is estimated using aftershock data most of the analyzed events are from the vicinity of the main central thrust mct which is a well defined tectonic discontinuity in the himalayas the method of a single backscattering model is employed to calculate frequency dependent values of coda q q c a total of 30 aftershock events are used for q c estimation at central frequencies 1 5 3 6 9 12 18 and 24 hz through five lapse time windows from 10 to 50 sec starting at double the travel time of the s wave the observed q c is strongly dependent on frequency which indicates that the region is seismically and tectonically active with high heterogeneities the variation of q c has also been estimated at different lapse times to observe its effect with depth the variation of q c with frequency and lapse time shows that the lithosphere becomes more homogeneous with depth q c values for higher frequencies increase very fast with depth within about the top 63 km of the lithosphere and then become more or less constant beyond this depth this indicates that turbidity at higher frequency decays very fast with depth and the mantle may be transparent to high frequency waves the variation of q c at 1 5 hz with lapse time matches quite well with those predicted by gusev 1995 however the frequency parameter n in the relation q c q 0 f n where q 0 q c at 1 hz does not follow the expected pattern given in his model this could be due to faster depth decay of turbidity as mentioned previously

the deglaciation of the americas during the last glacial termination this paper reviews current understanding of deglaciation in north central and south america from the last glacial maximum to the beginning of the holocene together with paleoclimatic and paleoceanographic data we compare and contrast the pace of deglaciation and the response of glaciers to major climate events during the global last glacial maximum glgm 26 5 19 ka average temperatures decreased 4 to 8 c in the americas but precipitation varied strongly throughout this large region many glaciers in north and central america achieved their maximum extent during the glgm whereas others advanced even farther during the subsequent heinrich stadial 1 hs 1 glaciers in the andes also expanded during the glgm but that advance was not the largest except on tierra del fuego hs 1 17 5 14 6 ka was a time of general glacier thickening and advance throughout most of north and central america and in the tropical andes however glaciers in the temperate and subpolar andes thinned and retreated during this period during the bolling allerod interstadial b a 14 6 12 9 ka glaciers retreated throughout north and central america and in some cases completely disappeared many glaciers advanced during the antarctic cold reversal acr 14 6 12 9 ka in the tropical andes and patagonia there were small advances of glaciers in north america central america and in northern

a continuous record of vegetation fire regime and climatic changes in northwestern patagonia spanning the last 25 000 years abstract we present a high resolution precisely dated terrestrial paleovegetation paleoclimate record from lago pichilaguna northwestern patagonia 40 44 s which spans continuously from the last glacial maximum lgm to the present we find abundant and continuous presence of arboreal pollen chiefly nothofagus during the lgm accompanied by other trees shrubs and alpine herbs these results suggest subantarctic parkland and or scattered woodlands under a cold and hyperhumid climate during the lgm 25 000 17 800 cal yr bp with expansion of nothofagus under relatively warm interstadial conditions between 25 000 and 19 200 cal yr bp this was followed by cooling and a precipitation increase between 19 200 and 17 800 cal yr bp which was contemporaneous with the youngest lgm advance of andean glaciers in the region and maximum influence of the southern westerly wind sww the last glacial termination t1 started at 17 800 cal yr bp and featured the spread of thermophilous trees and ferns characteristic of north patagonian rainforests along with lake level lowering these results suggest a warm pulse and southward shift of the sww concurrent with a rapid collapse of andean glacier lobes subsequent changes led to the establishment of closed canopy rainforests under peak interstadial warmth between 16 000 and 15 000 cal yr bp we detect a shift to cold wet conditions during the antarctic cold reversal 14 800 12 700 cal yr bp and a precipitation decline during younger dryas time followed by maximum temperature relatively lower lake level and minimum sww influence between 11 300 and 7700 cal yr bp precipitation then rose punctuated by centennial scale variations since 6200 cal yr bp chilean european deforestation and spread of invasive exotic species started at 350 cal yr bp aided by fire we conclude that temperate rainforests have persisted with little interruption since t1 with major changes in floristic composition driven by climate change and fires rainforest composition and heterogeneity declined in response to chilean european disturbance during the 1600s and intensified since the 1800s these events constitute the fastest largest magnitude vegetation changes of the last 25 000 years

glacial geomorphology of the torres del paine region southern patagonia implications for glaciation deglaciation and paleolake history abstract the processes affecting paleoclimate variability and pleistocene glacial landscape development in the southern mid latitudes remain poorly understood in part because of the scarcity of comprehensive well studied records glacial landforms are invaluable for reconstructing past ice sheet climate and associated environmental changes along the southern andes but there are significant spatial and temporal gaps in existing data in this paper we present new geomorphic and sedimentologic analyses including surficial maps for the torres del paine region 51 s 73 w southern south america our findings provide a new framework for understanding changes in the regional glacier history and pleistocene landscape development glacial extent during the local last glacial maximum lgm remains unknown but new chronological data supported by geomorphic evidence afford evidence for a larger ice sheet at torres del paine than previously assumed deglaciation from the local lgm was underway by 17 400 200 1 cal yr bp as opposed to previous suggestions we have found that most of the moraines fringing the lakes in the torres del paine national park were deposited during a late glacial expansion that occurred between 14 100 and 12 500 cal yr bp late glacial advances also have been documented recently for the ultima esperanza and lago argentino basins to the south and north of torres del paine respectively suggesting an overall regional ice response to a climate signal the tehuelche paleolake accompanied each of the ice sheet fluctuations in torres del paine new data document at least three main phases of this paleolake which drained eastward to the atlantic ocean while the andes gaps were blocked with ice during the late phase of glacial lake formation when water levels reached 125 155 m a s l the lake likely merged with paleolake consuelo in the ultima esperanza area at the end of the last glaciation lake tehuelche in torres del paine had drained into the pacific ocean by the late glacial period suggesting that ice southwest of torres del paine may have retreated back into the mountains by this time

late glacial holocene climate of the lake district of chile pollen evidence from a 350 cm section of a fen in a moraine belt at rucanancu 39 33 s 72 18 w bears on the controversy regarding interpretation of late glacial and holocene climate in midlatitude chile earlier pollen studies indicating a cooling trend between approximately 11 000 and 10 000 yr b p disagreed with observations of glacier fluctuations which show continuous glacier wastage and by inference warming after 12 500 yr b p and possibly earlier up until neoglaciation beginning after 6850 yr b p fossil beetle assemblage data in this time range support the interpretation of climate made from the observed glacier behavior at rucanancu a pollen assemblage containing upper montane podocarp podocarpus andinus in quantities reaching 34 and dating between 10 440 and 10 000 yr b p implies a cold climate with summer temperatures possibly 5 8 c lower than today s holocene warming began afterward later than the glacier and beetle records indicate and continued until at least 8350 yr b p as suggested by the sequence of assemblages dominated by myrtaceae by aextoxicon punctatum and by gramineae a subsequent assemblage of nothofagus obliqua type implies an increase of moisture until 6960 yr b p following which n dombeyi type under a cool and humid neoglacial climate became dominant

trans pacific glacial response to the antarctic cold reversal in the southern mid latitudes abstract elucidating the timing and regional extent of abrupt climate events during the last glacial interglacial transition 18 11 5 ka is critical for identifying spatial patterns and mechanisms responsible for large magnitude climate events the record of climate change in the southern hemisphere during this time period however remains scarce and unevenly distributed we present new geomorphic chronological and equilibrium line altitude ela data from a climatically sensitive mountain glacier at monte san lorenzo 47 s central patagonia twenty four new cosmogenic 10be exposure ages from moraines provide a comprehensive glacial record in the mid latitudes of south america which constrain the timing spatial extent and magnitude of glacial fluctuations during the antarctic cold reversal acr 14 5 12 9 ka rio tranquilo glacier advanced and reached a maximum extent at 13 9 0 7 ka three additional inboard moraines afford statistically similar ages indicating repeated glacier expansions or marginal fluctuations over the acr our record represents the northernmost robust evidence of glacial fluctuations during the acr in southern south america documenting not only the timing of the acr maximum but also the sequence of glacier changes within this climate event based on ela reconstructions we estimate a cooling of 1 6 1 8 c at the peak of the acr the rio tranquilo record along with existing glacial reconstructions from new zealand 43 s and paleovegetation records from northwestern 41 s and central west 45 s patagonia suggest an uniform trans pacific glacier climate response to an acr trigger across the southern mid latitudes we posit that the equatorial migration of the southern westerly winds provides an adequate mechanism to propagate a common acr signal across the southern hemisphere

radiocarbon chronology of the late glacial puerto bandera moraines southern patagonian icefield argentina abstract we report radiocarbon dates that constrain the timing of the deposition of the late glacial puerto bandera moraine system alongside the western reaches of lago argentino adjacent to the southern patagonian icefield close maximum limiting radiocarbon ages n 11 for glacier advance into the outer moraines with a mean value of 11 100 60 14 c yrs bp 12 990 80 cal yrs bp were obtained from wood in deformation soft till exposed beneath flow and lodgment till in bahia del quemado on the northeast side of brazo norte north branch of western lago argentino other exposures of this basal deformation till in bahia del quemado reveal incorporated clasts of peat along with larger inclusions of deformed glaciofluvial and lacustrine deposits radiocarbon dates of wood included in these reworked peat clasts range from 11 450 45 14 c yrs bp to 13 450 150 14 c yrs bp 13 315 60 to 16 440 340 cal yrs bp the implication is that during this interval glacier fronts were situated inboard of the puerto bandera moraines with the peat clasts and larger proglacial deposits being eroded and then included in the basal till during the puerto bandera advance minimum limiting radiocarbon ages for ice retreat come from basal peat in cores sampled in spillways and depressions generated during abandonment of the puerto bandera moraines glacier recession and subsequent plant colonization were initiated close behind different frontal sectors of these moraines prior to 10 750 75 14 c yrs bp 12 660 70 cal yrs bp east of brazo rico 10 550 55 14 c yrs bp 12 490 80 cal yrs bp in peninsula avellaneda and 10 400 50 14 c yrs bp 12 280 110 cal yrs bp in bahia catalana in addition a radiocarbon date indicates that by 10 350 45 14 c yrs bp 12 220 110 cal yrs bp the brazo norte lobe or former upsala glacier had receded well up the northern branch of lago argentino to a position behind the herminita moraines furthermore glacier termini had receded to just outboard of the outer holocene moraines at lago frias and lago pearson anita prior to 10 400 40 14 c yrs bp 12 270 100 cal yrs bp and 9040 45 14 c yrs bp 10 210 50 cal yrs bp respectively the most extensive recession registered during the early holocene was in agassiz este valley where the upsala glacier had pulled back behind the outer holocene moraine reaching close to the present day glacier terminus before 8290 40 14 c yrs bp 9300 80 cal yrs bp the radiocarbon dated fluctuations of the lago argentino glacier in late glacial time given here are in accord with changes in ocean mixed layer properties predominately temperature derived from the isotopic record given here of odp core 1233 taken a short distance off shore of the chilean lake district it also matches recently published chronologies of late glacial moraines in the southern alps of new zealand on the opposite side of the pacific ocean from lago argentino finally the timing of the late glacial reversal of the lago argentino glacier fits the most recent chronology for the culmination of the antarctic cold reversal acr in the deuterium record of the epica dome c ice core from high on the east antarctic plateau therefore we conclude that the climate signature of the acr was widespread in both the ocean and the atmosphere over at least the southern quarter of the globe

glacier expansion in central patagonia during the antarctic cold reversal followed by retreat and stabilisation during the younger dryas abstract the spatial temporal footprint of millennial scale climate events during the last glacial interglacial transition can yield insights into the underlying drivers of climate change but remains poorly resolved in patagonia here we assess the glacier response to abrupt cold events and palaeolake evolution using geomorphological mapping along with 10 b e ages and optically stimulated luminescence ages from near lago belgrano 47 9 s on the eastern side of monte san lorenzo the former belgrano glacier was sustained by a climatically sensitive ice cap making the site ideal for investigating the glacier response to abrupt cold reversals our data reveal an extensive re advance at 13 1 0 6 ka consistent with cooling and increased precipitation during the antarctic cold reversal acr subsequently ice retreated by at least 10 km and created an ice dammed proglacial lake in the belgrano valley rapid recession was punctuated by smaller advances still stands sufficient to maintain an ice dam for the palaeolake and deposit a lateral moraine dated at 12 4 0 3 ka during the younger dryas yd the final withdrawal of glaciers to the mountains allowed the palaeolake to drain and resulted in an atlantic pacific drainage reversal this marks the final separation of the patagonian ice sheet into the individual ice fields at the yd holocene transition our data demonstrate the dominant acr climate signal in central patagonia but also reveals a co occurrence of the northern hemisphere yd signal albeit of smaller magnitude the acr re advance was primarily climatically controlled but its relative magnitude was likely a consequence of ice divide migration and ice flow re routing during the break up of the patagonian ice sheet

late quaternary tephrostratigraphy of southern chile and argentina abstract the southern and austral volcanic zones of the andes comprise 74 volcanic centres with known post glacial activity at least 21 of these have had one or more large explosive eruptions in the late quaternary dispersing tephra over vast areas these tephra layers therefore have great potential as tephrochronological marker horizons in palaeoenvironmental studies in southern chile and argentina a region that is particularly useful to study climate dynamics of the southern hemisphere however to date tephrochronology has rarely been fully utilised in this region as a correlation and dating tool here we review the existing post glacial tephrostratigraphic record of the southern and austral volcanic zones and compile a database of known occurrences of tephra from these volcanoes in ice and lacustrine marine peat and cave sediment records we address the inconsistencies in and revisions of the tephrostratigraphies presented in prior literature and discuss the challenges in correlating tephras and the limitations of the tephrostratigraphic record in this area this study highlights the many gaps that still exist in our knowledge of the eruptive histories of these volcanoes but also reveals the largely under utilised potential of tephra as a correlation tool in this region this is exemplified by the severe lack of adequate geochemical analysis of tephra layers preserved in many lacustrine and peat sediment sections which are particularly important tephrostratigraphic records in southern chile and argentina due to the paucity of surface preservation

source parameters of the 1980 mammoth lakes california earthquake sequence from the more than 1500 mammoth lakes earthquakes recorded on three component digital seismographs spudich et al 1981 150 were used in an analysis of the locations mechanism and source parameters a composite fault plane solution of nine earthquakes 3 9 m 5 1 defines a right lateral strike slip mechanism on a steeply dipping nearly east west plane striking s75 e or left lateral strike slip on a nearly north south plane striking n10 e vertical cross sections of well located aftershocks indicate possibly three east west planes that coincide with the locations of the four largest earthquakes with ml 6 0 using the spectral analysis of s waves brune 1970 source parameters for 67 earthquakes were determined forty eight had magnitudes greater than or equal to 3 0 seismic moments ranged from 9 20 1018 dyn cm to 2 33 1024 dyn cm earthquakes with seismic moment greater than about 1 0 1021 dyn cm had nearly constant stress drops 50 bars earthquakes with seismic moment less than about 1 0 1021 dyn cm had stress drops that apparently decrease as seismic moment decreases

changes in fire regimes since the last glacial maximum an assessment based on a global synthesis and analysis of charcoal data fire activity has varied globally and continuously since the last glacial maximum lgm in response to long term changes in global climate and shorter term regional changes in climate vegetation and human land use we have synthesized sedimentary charcoal records of biomass burning since the lgm and present global maps showing changes in fire activity for time slices during the past 21 000 years as differences in charcoal accumulation values compared to pre industrial there is strong broad scale coherence in fire activity after the lgm but spatial heterogeneity in the signals increases thereafter in north america europe and southern south america charcoal records indicate less than present fire activity during the deglacial period from 21 000 to 11 000 cal yr bp in contrast the tropical latitudes of south america and africa show greater than present fire activity from 19 000 to 17 000 cal yr bp and most sites from indochina and australia show greater than present fire activity from 16 000 to 13 000 cal yr bp many sites indicate greater than present or near present activity during the holocene with the exception of eastern north america and eastern asia from 8 000 to 3 000 cal yr bp indonesia and australia from 11 000 to 4 000 cal yr bp and southern south america from 6 000 to 3 000 cal yr bp where fire activity was less than present regional coherence in the patterns of change in fire activity was evident throughout the post glacial period these complex patterns can largely be explained in terms of large scale climate controls modulated by local changes in vegetation and fuel load

the last glacial termination a major puzzle of paleoclimatology is why after a long interval of cooling climate each late quaternary ice age ended with a relatively short warming leg called a termination we here offer a comprehensive hypothesis of how earth emerged from the last global ice age a prerequisite was the growth of very large northern hemisphere ice sheets whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation the southern hemisphere westerlies shifted poleward during each northern stadial producing pulses of ocean upwelling and warming that together accounted for much of the termination in the southern ocean and antarctica rising atmospheric co2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres

the magnitude frequency distribution of earthquakes recorded with deep seismometers at cajon pass southern california abstract the cumulative b value the slope of the gutenberg richter relationship between earthquake occurrence rate and magnitude is commonly found to be constant 1 network catalogues however reveal a decrease at small magnitudes b value is not just an artifact of catalogue incompleteness but that small earthquakes are really not as numerous as a constant b value extrapolated from larger events would predict in the cajon pass area southern california the b value of seismicity recorded by the local network scsn appears to decrease below about m l 1 6 in order to investigate whether this decrease is real or simply represents the network detection threshold we use seismicity recorded by the deep 1 5 and 2 5 km seismometers deployed in the cajon pass scientific drillhole between april 1992 and october 1994 the maximum amplitudes recorded downhole are compared to scsn magnitudes for events recorded by the network to determine the relationship between amplitude and m l as a function of hypocentral distance from the borehole magnitudes are then calculated for 1300 earthquakes which occurred within 40 km of the borehole magnitude frequency curves are calculated for those events within 18 km of the borehole and a constant b value is observed to m l 0 5

scale dependence in earthquake phenomena and its relevance to earthquake prediction abstract the recent discovery of a low velocity low q zone with a width of 50 200 m reaching to the top of the ductile part of the crust by observations on seismic guided waves trapped in the fault zone of the landers earthquake of 1992 and its identification with the shear zone inferred from the distribution of tension cracks observed on the surface support the existence of a characteristic scale length of the order of 100 m affecting various earthquake phenomena in southern california as evidenced earlier by the kink in the magnitude frequency relation at about m3 the constant corner frequency for earthquakes with m below about 3 and the sourcecontrolled fmax of 5 10 hz for major earthquakes the temporal correlation between coda q 1 and the fractional rate of occurrence of earthquakes in the magnitude range 3 3 5 the geographical similarity of coda q 1 and seismic velocity at a depth of 20 km and the simultaneous change of coda q 1 and conductivity at the lower crust support the hypotheses that coda q 1 may represent the activity of creep fracture in the ductile part of the lithosphere occurring over cracks with a characteristic size of the order of 100 m the existence of such a characteristic scale length cannot be consistent with the overall self similarity of earthquakes unless we postulate a discrete hierarchy of such characteristic scale lengths the discrete hierarchy of characteristic scale lengths is consistent with recently observed logarithmic periodicity in precursory seismicity

renewed glacial activity during the antarctic cold reversal and persistence of cold conditions until 11 5 ka in southwestern patagonia resolving the timing direction and magnitude of paleoclimate changes in the southern midlatitudes is a prerequisite for determining the mechanisms underlying abrupt and widespread climate changes between the hemispheres during the last glacial interglacial transition lgit this issue is still debated with previous studies producing apparently discordant fi ndings here we show evidence for a glacial readvance and a cold episode between ca 14 8 and 12 6 ka in southwestern patagonia 50 s contemporaneous with the antarctic cold reversal this was followed by ice recession under cold but relatively milder conditions until ca 11 5 ka when paleovegetation records indicate the onset of warm interglacial conditions these fi ndings differ from those reported in northern patagonia 40 s where deteriorating conditions before 13 5 ka were followed by the coldest part of the lgit that lasted until ca 11 5 ka we interpret the apparent blend of greenlandic and antarctic cold phases as evidence for their co occurrence in the southern middle latitudes in patagonia and hypothesize that the position of the antarctic polar front modulated the strength of these cold events in regions to the north or south of it

timing and structure of vegetation fire and climate changes on the pacific slope of northwestern patagonia since the last glacial termination abstract by virtue of its location in the southern mid latitudes northwestern patagonia 40 44 s offers the opportunity to unravel the mechanisms involved in the initiation and propagation of paleoclimate signals of hemispheric and global significance of particular importance is deciphering the evolution of the southern westerly winds sww considering their influence at continental zonal hemispheric and global scale here i present a multi decadal record from lago proschle a small closed basin lake located on the pacific slope of northwestern patagonia to examine the timing and structure of vegetation fire and climate change along a continuum since the onset of the last glacial termination t1 the record shows rapid glacier recession during t1 reaching the western andean foothills in 400 years or less nothofagus dominated forests established between 17 4 17 ka followed by closed canopy north patagonian rain forests nprf with shade tolerant thermophilous trees between 16 3 15 4 ka these changes suggest an abrupt warming trend and an increase in precipitation at 16 3 ka associated with a northward shift of the sww subsequent increases in cold tolerant hygrophilous trees between 15 4 12 8 ka imply a shift to cold more humid conditions during the antarctic cold reversal suggesting stronger sww influence this was followed by stand replacing fires brought by a sudden decline in summer precipitation at 12 8 ka associated with a millennial scale southward shift of the sww which was contemporaneous with the onset of the younger dryas dominance of thermophilous summer drought tolerant valdivian rainforest trees and high fire activity ensued between 10 3 7 8 ka suggesting peak warmth and overall decline in annual precipitation associated with weakening of the sww during the early holocene a multi millennial cooling and wetting trend started at 7 8 ka brought by stronger sww influence followed by recurrent centennial scale variations in temperature and precipitation starting at 6 4 ka deforestation fire and spread of non native herbs by chilean european settlers began during the late 18th century abrupt vegetation changes in the lago proschle record were driven by rapid climate changes over the last 17 400 years amplified in some instances by fire disturbance

attenuation models qp and qs in three dimensions of the southern california crust inferred fluid saturation at seismogenic depths we analyze high dynamic range waveform spectra to determine t values for both p and s waves from earthquakes in southern california we invert the t values for three dimensional 3 d frequency independent q p and q s regional models of the crust the models have 15 km horizontal grid spacing and an average vertical grid spacing of 4 km down to 22 km depth and extend from the u s mexico border to the coast ranges in the south and sierra nevada in the north in general qp and qs increase rapidly with depth consistent with crustal densities and velocities the 3 d q p and q s models image the major tectonic structures and to a much lesser extent the thermal structure of the southern california crust the near surface low q p and q s zones coincide with major sedimentary basins such as the san bernardino chino san gabriel valley los angeles ventura and santa maria basins and the salton trough in contrast at shallow depths beneath the peninsular ranges southern mojave desert and southern sierras we image high q p and q s zones which correspond to the dense and high velocity rocks of the mountain ranges several clear transition zones of rapidly varying q p and q s coincide with major late quaternary faults and connect regions of high and low q p and q s at midcrustal depths the q p and q s exhibit modest variation in slightly higher and lower qp or qs zones which is consistent with reported crustal reflectivity in general for the southern california crust q s q p is greater than 1 0 suggesting partially fluid saturated crust a few limited regions of q s q p less than 1 0 correspond to areas mostly outside the major sedimentary basins including areas around the san jacinto fault suggesting a larger reduction in the shear modulus compared to the bulk modulus or almost complete fluid saturation

radiated seismic energy from coda measurements and no scaling in apparent stress with seismic moment 1 the seismic coda consists of scattered waves that leave the earthquake source in a variety of directions the averaging of source radiation that results leads to stable ground motion spectra that we use as the basis for a robust measurement of radiated wave energy we apply an empirical green s function egf method to the seismic coda in order to investigate scaling of the radiated seismic energy we correct for path effects in the spectra of earthquakes by using a stack of closely located small earthquakes as an egf we apply this approach to four earthquake sequences in western north america that span a magnitude range from mw 3 0 mw 7 1 our estimates of scaled energy are consistent with independent measurements where available we find no dependence in individual seismic energy estimates on source station distance which validates the egf approximation we find that a constant scaled energy of 3 5 10 5 provides a reasonable fit to the data with no dependence of the scaled energy on seismic moment

vegetation fire and climate change in central east isla grande de chiloe 43 s since the last glacial maximum northwestern patagonia abstract we present a detailed record from lago lepue to examine vegetation climate and fire regime changes since the last glacial maximum lgm in central east isla grande de chiloe 43 s northwestern patagonia precipitation in this region correlates with the intensity of the southern westerly winds sww allowing reconstruction of past sww behavior through precipitation sensitive sensors recession from the lgm glacier margins exposed the central east sector of isla grande de chiloe by 17 800 cal yr bp followed by the immediate colonization of pioneer cold resistant herbs shrubs and rapid establishment of closed canopy nothofagus forests by 17 000 cal yr bp broad leaved temperate rainforests have persisted since then with compositional changes driven by changes in temperature hydrologic balance and disturbance regimes we detect low lake levels and enhanced fire activity between 800 2000 4000 4300 8000 11 000 and 16 100 17 800 cal yr bp implying southward shifts and or weaker sww flow that alternated with cold humid phases with muted fire activity covariation in paleoclimate trends revealed by the lago lepue record with tropical and antarctic records since the lgm suggests that the sww have been a highly dynamic component of the climate system capable of linking climate changes from low and high southern latitudes during the last glacial termination and the current interglacial

centennial and millennial scale hydroclimate changes in northwestern patagonia since 16 000 yr bp abstract we examine hydroclimate changes at centennial millennial timescales since 16 000 yr bp in northwestern patagonia based on the pollen and charcoal record from lago el salto a small closed basin lake located in the chilean lake district 41 38 48 02 s 73 5 48 42 w we observe cold wet conditions between 14 500 16 000 yr bp followed by further cooling with increased precipitation until 13 000 yr bp enhanced precipitation seasonality and or variability between 11 600 13 000 yr bp and an extended warm and dry interval between 7600 and 11 300 yr bp with peak paleofire activity colder and wetter than present conditions and muted paleofire activity prevail between 5300 and 7600 yr bp followed by alternating cold wet and centennial scale warm dry phases starting at 5300 yr bp with three conspicuous megadroughts since 2500 yr bp the most recent megadrought occurred during the medieval climate anomaly we identify a cold reversal that spans the antarctic cold reversal acr and the younger dryas yd chrons with stronger than present westerly influence during the former and enhanced variability during the latter these results extend the northern limit of strong cooling and increase in precipitation during the acr and the southern limit of influence of strong hydrologic variations during the yd in terrestrial environments suggesting an overlap in the spheres of influence of processes originating from southern and northern polar latitudes an extended warm southern westerly wind sww minimum interval is evident between 7600 and 11 300 yr bp followed by a rapid shift to cool moist conditions between 5300 and 7600 yr bp brought by a mid holocene sww maximum since then we observe centennial scale hydroclimate variability which has driven biodiversity and fire regime shifts of evergreen temperate rainforests

seismic albedo from the total seismic energy dependence on hypocentral distance in southern california abstract scattering and absorption of seismic waves have been studied in southern california to determine their respective contributions to the measured apparent attenuation we measured the total seismic energy from the onset of the s waves for local earthquakes recorded at stations on granitic rock reduced to a common source by eliminating the source and site effect by the coda method then applied wu s method based on the radiative transfer theory which has the facility to separate the intrinsic absorption from the scattering effect the observed total energy as a function of hypocentral distance exhibits a striking behavior increasing to a maximum at about 50 km then decreasing exponentially as a function of hypocentral distance decay of the total energy as a function of distance is remarkably similar for all frequency bands centered at 1 5 3 0 6 0 and 12 0 hz in good agreement with earlier results on q of coda and s waves in southern california comparison with wu s theoretical plots which shows curves that differ in shape because of differences in seismic albedo if b 0 s s a where s and a are the scattering and absorption coefficients respectively leads to the conclusion that the s wave energy is primarily redistributed in space by scattering rather than intrinsically absorbed by the earth our results from southern california agree with those of toksoz et al who found seismic albedo b0 to be 0 8 0 9 in eastern north america coda q in southern california however closely agrees with scattering q using wu s model in disagreement with the conclusions of toksoz et al for eastern north america where coda q is close to the absorptive q obtained from the total energy study the agreement between wu s theoretical curves and our observations is not perfect departure of the observed curves from the theory may be due in part to inhomogeneous distribution of scatterers and absorbers as well as non isotropic scattering we need more realistic models which can also account for inhomogeneous bounded media

stability of coda q in the region of parkfield california view from the u s geological survey parkfield dense seismograph array many investigators have proposed that changes in the rate at which the coda decays may be an intermediate term precursor to moderate to large earthquakes parkfield california on the san andreas fault is a promising location for studying premonitory changes in coda q qc because a large earthquake is likely to occur there we have investigated qc using recordings from the u s geological survey parkfield dense seismograph array which is a digital array with 14 triaxial sensors and an aperture of about 1 km for each earthquake we can measure qc from up to 42 recordings their average is more stable than the measurement from a single station using clustered seismicity we have developed criteria for selecting events and reducing scatter in the measurement the qc value determined from a seismogram depends on the position and length of the analysis window thus qc should always be measured from the same length window starting at the same lapse time regardless of the source location in addition the band limited signal to noise ratio at the end of the analysis window is important qc determined in two frequency bands 4 8 hz and 8 16 hz from a tight cluster of 26 events which occurred between december 1989 and january 1994 has not changed despite m 4 7 and m 4 6 events in october 1992 and november 1993 qc measured from local events 60 km in three frequency bands shows larger scatter but has also not changed during this period for monitoring qc observations should include array averaged measurements from a single lapse time because qc measurements made using an analysis window that starts at a constant multiple of the s wave lapse time depend on epicentral distance a procedure combining the evaluation of the time and distance dependences of qc also gives stable observations

spectral analysis of k net and kik net data in japan part ii on attenuation characteristics source spectra and site response of borehole and surface stations abstract in this study we apply a nonparametric spectral inversion scheme to a data set of accelerograms recorded by the k net and kik net networks in japan in order to derive attenuation characteristics source spectra and site response for this purpose we use a total of more than 67 000 s wave records from 2178 earthquakes m jma 2 7 8 obtained at 1555 stations at the earth s surface and more than 29 000 records from 1826 events recorded at 637 borehole stations at depths of 100 to 3000 m attenuation characteristics are investigated in five separate regions showing that crustal q depicts lower values in central compared to southern japan and a significant frequency dependence is observed in every region the source spectra follow the 2 model with higher stress drops for subcrustal earthquakes as compared with crustal ones while strong amplification effects dominate the site contributions for the surface sensors those for the borehole sensors are characterized by smaller variability nevertheless consistent with observations from deconvolution of borehole surface recording pairs downgoing wave effects are visible in the site contributions for many borehole stations finally the site amplification functions obtained at the surface are compared with surface to borehole s b and horizontal to vertical h v spectral ratios showing that the s b ratios generally provide better estimates of the horizontal amplification than the h v ratios due to amplification of the vertical component of ground motion

comprehensive analysis of earthquake source spectra in southern california we compute and analyze p wave spectra from earthquakes in southern california between 1989 and 2001 using a method that isolates source receiver and path dependent terms we correct observed source spectra for attenuation using both fixed and spatially varying empirical green s function methods estimated brune type stress drops for over 60 000 m l 1 5 to 3 1 earthquakes range from 0 2 to 20 mpa with no dependence on moment or local b value median computed stress drop increases with depth in the upper crust from about 0 6 mpa at the surface to about 2 2 mpa at 8 km where it levels off and remains nearly constant in the midcrust down to about 20 km however the results at shallow depths could also be explained as reduced rupture velocities near the surface rather than a change in stress drop spatially coherent variations in median stress drop are observed with generally low values for the imperial valley and northridge aftershocks and higher values for the eastern transverse ranges and the north end of the san jacinto fault we find no correlation between observed stress drop and distance from the san andreas and other major faults significant along strike variations in stress drop exist for aftershocks of the 1992 landers earthquake which may correlate with differences in main shock slip

warming and glacier recession in the rakaia valley southern alps of new zealand during heinrich stadial 1 abstract the termination of the last ice age featured a major reconfiguration of earth s climate and cryosphere yet the underlying causes of these massive changes continue to be debated documenting the spatial and temporal variations of atmospheric temperature during deglaciation can help discriminate among potential drivers here we present a 10be surface exposure chronology and glaciological reconstruction of ice recession following the last glacial maximum lgm in the rakaia valley southern alps of new zealand innermost lgm moraines at big ben have an age of 17 840 240 yrs whereas ice marginal moraines or ice molded bedrock surfaces at distances up valley from big ben of 12 5 km lake coleridge 25 km castle hill 28 km double hill 43 km prospect hill and 58 km reischek knob have ages of 17 020 70 yrs 17 100 110 yrs 16 960 370 yrs 16 250 340 yrs and 15 660 160 yrs respectively these results indicate extensive recession of the rakaia glacier which we attribute primarily to the effects of climatic warming in conjunction with geomorphological maps and a glaciological reconstruction for the rakaia valley we use our chronology to infer timing and magnitude of past atmospheric temperature changes compared to an overall temperature rise of 4 65 c between the end of the lgm and the start of the holocene the glacier recession between 17 840 and 15 660 yrs ago is attributable to a net temperature increase of 4 0 c from 6 25 to 2 25 c accounting for 86 of the overall warming approximately 3 75 c 70 of the warming occurred between 17 840 and 16 250 yrs ago with a further 0 75 c 16 increase between 16 250 and 15 660 yrs ago a sustained southward shift of the subtropical front stf south of australia between 17 800 and 16 000 yrs ago coincides with the warming over the rakaia valley and suggests a close link between southern ocean frontal boundary positions and southern mid latitude climate most of the deglacial warming in the southern alps occurred during the early part of heinrich stadial 1 hs1 of the north atlantic region because the stf is associated with the position of the westerly wind belt our findings support the concept that a southward shift of earth s wind belts accompanied the early part of hs1 cooling in the north atlantic leading to warming and deglaciation in southern middle latitudes

depth dependent seismic attenuation in the granada zone southern spain abstract coda q estimates for the granada basin southern spain are obtained by analyzing earthquakes occurring within or close to the borders of this area the data set is composed of 54 earthquakes with local magnitudes ranging between 2 2 and 4 0 and with epicentral distances to the nearest station smaller than 10 km a single scattering process is assumed coda q values obtained show a clear dependence on frequency according to the relationship q q o f n where n ranges from 0 81 to 0 89 after removing the main site effects and discussing the possible multiple scattering influence the lapse time dependence is interpreted as due to attenuation variations with depth this result agrees with the variation of coda q obtained by using different sets of events with increasing hypocentral depth ranges

attenuation of high frequency shear waves in the crust measurements from new york state south africa and southern california we compare the attenuation of high frequency 3 30 hz shear waves for crustal paths in new york state south africa and southern california over source receiver distances of about 10 400 km the data consist of digital recordings of s waves 5 100 km and lg waves 100 400 km produced by earthquakes we use a coda normalization method to remove the effects of site amplification and source excitation from the amplitudes of the s and lg waves over the entire distance range studied 10 400 km the amplitude decay of 3 hz shear wave energy is considerably less for the tectonicaily stable areas of new york and south africa than for the tectonicaily active region of southern california high frequency 30 hz s wave attenuation is significantly less for new york and south africa than for southern california for distances between 15 and 90 km we parameterize the decay with distance r of coda normalized shear wave amplitudes with a frequency independent q and geometrical spreading exponent where geometrical spreading is proportional to r for new york state the s wave amplitude decay 3 30 hz is well described by a frequency independent q of 2100 330 490 and of 1 3 0 1 the decay of lg wave amplitudes from 3 to 15 hz in the new york state region is fit with a frequency independent q of 1600 280 330 of 0 70 0 2 the s wave amplitudes 3 30hz in south africa yield a q of 1500 190 380 and of 1 3 0 1 fixing the geometrical spreading at r 0 5 produces an lg wave q estimate at 3 hz in south africa of 360 50 80 this lg wave q is low considering that south africa is a cratonic tectonicaily stable area the s wave amplitudes from southern california are described with a frequency independent q of 800 150 240 and a large geometrical spreading exponent of of 1 9 0 2 we find an lg wave q at 3 hz of 260 30 for southern california after constraining the geometrical spreading at r 0 5

residence time of diffuse waves in the crust as a physical interpretation of coda q application to seismograms recorded in mexico summary we consider a simple model for elastic wave propagation in the earth s litho sphere consisting of a heterogeneous and scattering crust overlying a homogeneous mantle that is we neglect backscattering from the upper mantle this rough condition is not strictly valid everywhere but this model allows us to investigate the effects of variations of diffracting properties between crust and mantle on the coda decay the free parameters describing the wave propagation are the mean free path of the waves and the intrinsic absorption in the crust in the framework of the radiative transfer theory we treat accurately jumps in s wave speed and the mean free path at the moho without intrinsic absorption this configuration yields a synthetic coda decay 1 texp 2 ft qc a form similar to that proposed by aki chouet 1975 to parametrize the observations the exponential decay in our purely elastic model is due to the partial leakage of diffuse energy into the mantle in order to test the applicability of our model we have determined the coda q parameter qc in the 1 15 hz frequency band from data recorded at four stations in mexico in the low frequency regime around 1 hz we suggest that the energy leakage significantly affects coda q whilst at higher frequencies around 10 hz the anelastic attenuation dominates a weak intrinsic absorption expressed by a frequency independent parameter qi of about 1000 accounts satisfactorily for the observed qc values in the whole frequency range our very simple model has only two free parameters and offers an attractive alternative physical interpretation of coda q in mexico this model is sufficient to interpret the coda observations according to our model in regions where the mean free path is much larger than the crustal thickness weakly heterogeneous crust the leakage effect should be small and the observed qc will mainly be due to the intrinsic absorption on the other hand when the mean free path is of the order of the crustal thickness strongly heterogeneous crust we predict a strong sensitivity of the decay rate of the coda to the crustal thickness this dependence may be important for the interpretation of the regional variations of coda q we propose introducing a new parameter d the residence time of diffuse energy in the crust which is physically more meaningful than a quality factor to quantify the leakage effect

temporal change in coda associated with the round valley california earthquake of november 23 1984 seven thousand seismograms of small earthquakes in the mammoth lakes bishop area were used to measure values of q from the decay of the earthquake coda these measurements were compared between events that occurred before and after the round valley earthquake m 5 7 we found that in regions near the main shock epicenter measurements of coda q 1 for earthquakes that occurred after the main shock were higher than for those earthquakes that occurred prior to the main shock the opposite behavior was found for regions farther away from the main shock namely lower coda q 1 after the main shock than before measurements of coda q 1 in the long valley caldera outside of the immediate source region of the earthquake were higher than in surrounding areas before the main shock but the difference disappeared after the occurrence of the main shock this indicates that the temporal variation in coda q 1 is comparable to its spatial variation the doughnut model seismicity quiescence surrounded by a zone of activity which was invoked for explaining the precursory seismicity pattern appears to be similar with the observed coda q 1 variation associated with the round valley earthquake the observed spatial variations in coda q 1 also help to reconcile conflicting results published in previous studies of the coda q 1 precursor

the deuterium excess records of epica dome c and dronning maud land ice cores east antarctica new high resolution deuterium excess d data from the two epica ice cores drilled in dronning maud land edml and dome c edc are presented here the main moisture sources for precipitation at edc and edml are located in the indian ocean and atlantic ocean respectively the more southward moisture origin for edml is reflected in a lower present day d value compared to edc the edml and edc isotopic records 18o and d show the main climate features common to the east antarctic plateau and similar millennial scale climate variability during the last glacial period however quite large 18o and d differences are observed during mis5 5 and the glacial inception with a long term behaviour a possibility for this long term difference could be related to uncertainties in past accumulation rate which are used in the glaciological models regional climate anomalies between the two sites during mis5 5 could also be consistent with the observed edml edc 18o and d gradient anomalies simulations performed with the general circulation model echam4 for different time slices provide a temporal temperature isotope slope for the edml region in fair agreement to the modern spatial slope tsite and tsource records are extracted from both ice cores using a modelling approach after corrections for past 18o seawater and elevation changes a limited impact of d on antarctic temperature reconstruction at both edml and edc has been found with a higher impact only at glacial inception the aim antarctic isotope maximum events in both ice cores are visible also after the source correction suggesting that these are real climate features of the glacial period the different shape of the aim events between edc and edml as well as some climate features in the early holocene points to a slightly different climate evolution at regional scale a comparison of our temperature reconstruction profiles with the aerosol fluxes show a strong coupling of the nssca fluxes with antarctic temperatures during glacial period and a tighter coupling of 18o and tsite with ssna flux at edml compared to edc during the glacial period and mis5 5

moment energy stress drop and source spectra of western united states earthquakes from regional coda envelopes we present a new method to estimate stable seismic source parameters such as energy moment and orowan stress drop using regional coda envelopes from as few as one broadband station we use the method to compute path and site corrected seismic moment rate spectra for 117 recent western united states earthquakes empirical green s function corrections were applied to our surface and body wave coda envelope measurements to generate s wave source spectra these source spectra provide stable single station estimates of radiated seismic energy es and seismic moment mo that for common events are in excellent agreement with network averaged estimates obtained using local and regional data teleseismic moment estimates are compatible with our regional results but teleseismic energy estimates appear to be nearly an order of magnitude low we estimated the seismic moment of events ranging between mw 2 2 and 7 3 and energy estimates for which we had measured at least 70 of the total energy generally events above mw 3 3 we use these estimates to examine the behavior of derived parameters such as the orowan stress drop 2 es mo while the earthquakes we studied have a small range in orowan stress drop generally between 0 1 and 20 mpa they show a strong tendency for orowan stress drop to increase with moment approximately as mo0 25 we believe this is a source effect and is not due to inadequate bandwidth or attenuation correction and note that this trend appears to continue for microearthquakes as described in a recent deep borehole study in southern california many of the large high stress drop earthquakes show complexity in their moment rate spectra near the corner frequency and cannot be fit by a simple square model instead above the first corner frequency the spectral decay ranges between f 1 0 and f 1 5 this leads to larger estimates of radiated energy than predicted with a simple square model and has implications for seismic hazard estimation coda envelopes have three main advantages over direct arrivals for estimating seismic moment and energy 1 coda amplitudes vary little with geology and source radiation anisotropy and allow accurate single station applications 2 path corrected coda amplitude measurements can be applied to very large regions allowing a comparison of source parameters throughout the western united states using a common methodology and stations 3 because long period coda can last for hours for large local and regional events it allows the analysis of seismograms with clipped early arrivals

expansion of magellanic moorland during the late pleistocene palynological evidence from northern isla de chiloe chile the late quaternary vegetation of northern isla de chiloe is inferred from palynological analysis of a section in the rio negro drainage 42 03 s 73 50 w at ca 30 500 yr b p maxima of astelia and donatia occurred suggesting wetland development from that time until ca 27 000 yr b p steppe indicators such as compositae gramineae dominated suggesting drier conditions after 27 000 yr b p the moorland shrub dacrydium gradually increased reaching a maximum by 18 000 yr b p at this time astelia increased again suggesting development of cushion bog during cold and wet conditions the glacial postglacial transition is characterized by a marked change from peaty sediments to clays a decrease in the cushion bog flora and the prevalence of gramineae compositae and swamp taxa this vegetation prevailed until ca 7000 yr b p when forest taxa became dominant the floristic pattern inferred from the pollen spectra of the rio negro section suggests that the late pleistocene vegetation of chiloe resembled modern magellanic moorland vegetation 52 56 lat s based on climatic conditions presently associated with magellanic moorland its occurrence in chiloe at low elevations during the late pleistocene implies a decrease in average temperature of at least 4 c and an increase in annual precipitation of at least 1500 mm

an 18 000 year long eruptive record from volcan chaiten northwestern patagonia paleoenvironmental and hazard assessment implications abstract the 2008 eruption of volcan chaiten vcha in northwestern patagonia was the first explosive rhyolitic eruption to have occurred within a century and provided an unprecedented scientific opportunity to examine all facets of the eruption ranging from magma rheology ascent rates to ash fall effects on biota and infrastructure up to very recently it was thought that the latest eruption prior to the 2008 event occurred c 9750 cal a bp although a number of researchers have recognised additional eruptive products but their stratigraphy age and geochemical attributes have not been systematically described and or recorded in this study we provide a detailed examination of andic cover beds and tephra bearing lake sequences located both proximally and distally to vcha which record a series of hitherto unknown rhyolitic eruptive products and place all previous observations firmly within a coherent stratigraphic framework through major and trace element glass shard geochemistry we are able to confidently verify eruptive source a total of 20 discrete tephra beds are recognised with at least 10 having widespread areal distributions and or depositional imprints broadly comparable to or greater than the 2008 tephra event this record indicates that vcha has been continuously but intermittently active as far back as the end of the last glacial maximum c 18 000 cal a bp with two dominant genetically related magma types and an intermediary mixed type before this the eruptive record has been largely obscured and or erased by widespread andean piedmont glaciation however based on the tempo of vcha activity over the last c 18 000 years older vcha eruptives can be anticipated to occur as well as future hazardous explosive events the new eruptive inventory will ultimately be useful for correlating equivalent aged sequences and refining long term eruptive tempo as well as corresponding temporal changes in magmatic evolution

have the southern westerlies changed in a zonally symmetric manner over the last 14 000 years a hemisphere wide take on a controversial problem the prevailing view in the palaeoclimate literature of the last 20 years is that the southern westerly winds sww were intensified over southern australia and tasmania during the warmer than present early holocene 11e8 ka at similar latitudes on the opposite side of the southern mid latitudes palaeoclimate studies have suggested a poleward shift of the northern edge of the westerlies and focusing at 49 s in southern south america this zonal asymmetry contrasts with the modern day zonal symmetry displayed by the sww and poses a formidable challenge to an understanding of the modes of climatic variability of the southern extra tropics this paper presents an updated synthesis of continuous radiocarbon dated palaeoenvironmental data from the westerlies zone of influence in all southern hemisphere continents synchronous multi millennial trends in moisture vegetation fire and hydrologic balance are remarkably consistent with the way the sww changes impact upon the climate in southern hemisphere landmasses in the modern climate considering the modern relationships between local precipitation and zonal wind speeds it is suggested that the sww changed in a zonally symmetric manner at multi millennial scale between 14 and 5 ka regional asymmetry develops after 5 ka across the southern hemisphere with a pattern of precipitation anomalies akin to the modern functioning of el nino e southern oscillation which started w6200 years ago

regionalization of crustal coda q in the continental united states a contour map of crustal q sub 0 values for the entire united states is presented based on a scattering model to explain the coda waves of local and near regional earthquakes these coda q sub 0 values are in good agreement with q of lg waves data are obtained from over 250 local earthquakes with most magnitudes between 3 0 and 5 0 recorded by 25 wwssn and 27 lrsm stations throughout the continental united states these two sets of data provide a range of frequencies from 0 5 to 3 5 hz a frequency dependence of q is observed in the range of frequencies considered a power law dependence of the form q q sub 0 f f sub 0 sup eta is assumed the value of frequency dependence eta is found to be maximum in the tectonically active western united states and least in the stable regions of the central and south central united states the lowest q sub 0 values are obtained in the western united states with values ranging from 140 to 200 in the coastal plains average crustal q sub 0 values for the basin and range province vary from 200 to 300 increasing gradually to 400 in the colorado plateau region q sub 0 valuesmore in the columbia plateau vary from 200 to 400 q sub 0 values increase very rapidly along the central and southern rocky mountains from 400 to 800 east of the rocky mountains q sub 0 values increase gradually in the interior plains to a maximum value of around 1300 in the mississippi embayment region farther east q sub 0 values decrease gradually to an almost constant value of 1000 along the appalachian mountains coastal regions of eastern and northeastern united states have a crustal q sub 0 value between 900 to 700 regions of north central and gulf coastal plains show low q sub 0 values ranging from 600 to 400 and less the source factor b f sub p a measure of the intensity of scattering was obtained for several different regions of the continental united states regions of high q sub 0 values exhibit low intensity of scattering less

deglacial changes of the southern margin of the southern westerly winds revealed by terrestrial records from sw patagonia 52 s much of the ongoing discussion regarding synchrony or bipolar asynchrony of paleoclimate events has centered on the timing and structure of the last glacial termination in the southern mid latitudes in particular the southwestern patagonian region 50 e55 s its location adjacent to the drake passage and near the southern margin of the southern westerly winds sww allows examining the postulated links between the southern oceanesww coupled system and atmospheric co2 variations through the last glacial termination results from two sites located in the ultima esperanza area 52

radiocarbon chronology of the last glacial maximum and its termination in northwestern patagonia abstract we examine the timing and magnitude of the last glacial maximum lgm and the last glacial termination lgt in northwestern patagonia situated in the middle latitudes of south america our data indicate that the main phase of the lgt began with abrupt warm pulses at 17 800 and 17 100 cal yrs bp accompanied by rapid establishment of evergreen temperate rainforests and extensive deglaciation of the andes within 1000 years this response shows that south american middle latitude temperatures had approached average interglacial values by 16 800 cal yrs bp the temperature rise in northwestern patagonia coincides with the beginning of major warming and glacier recession in the southern alps of new zealand at southern mid latitudes on the opposite side of the pacific ocean from this correspondence the warming that began at 17 800 cal yrs bp appears to have been widespread in middle latitudes of the southern hemisphere accounting for at least 75 of the total temperature recovery from the lgm to the holocene moreover this warming pulse is coeval with the first half of the heinrich stadial 1 hs1 in the north atlantic region hs1 featured a decline of north atlantic meridional overturning circulation a southward shift of the westerly wind belt in both hemispheres and of the intertropical convergence zone as well as a weakening of the asian monsoon along with the initiating trigger identifying the mechanisms whereby these opposing climate signals in the two polar hemispheres interacted whether through an oceanic or an atmospheric bipolar seesaw or both lies at the heart of understanding the lgt

covariability of the southern westerlies and atmospheric co2 during the holocene a suite of mechanisms has been proposed to account for natural variations in atmospheric co 2 during the holocene all of which have achieved limited success in reproducing the timing direction and magnitude of change recent modeling studies propose that changes in the latitudinal position and strength of the southern hemisphere westerly winds sww can greatly influence large scale ocean circulation and degassing of the deep ocean via changes in wind driven upwelling in the southern ocean the extent to which the hypothesized sww southern ocean coupled system could account for changes in atmospheric co 2 is uncertain because of a lack of observations on the behavior of the sww in the past the paucity of appropriate records of productivity changes in the southern ocean and our limited understanding of the sensitivity of the southern ocean biological and or physical system to sww forcing here we report a reconstruction of the behavior of the sww during the past 14 k y based on terrestrial ecosystem proxies from western patagonia south america the reconstructed variations in the intensity of zonal flow correspond to the timing and structure of atmospheric co 2 changes and are consistent with the modeled magnitude of co 2 changes induced by varying strengths of the sww the close match between data and models supports the view that the sww southern ocean coupled system underpins multimillennial co 2 variations during the current interglacial and possibly during glacial cycles over the past 800 k y

large scale control on the patagonian climate abstractpatagonia located in southern south america is a vast and remote region holding a rich variety of past environmental records but a small number of meteorological stations precipitation over this region is mostly produced by disturbances embedded in the westerly flow and is strongly modified by the austral andes uplift on the windward side leads to hyperhumid conditions along the pacific coast and the western slope of the andes in contrast downslope subsidence dries the eastern plains leading to arid highly evaporative conditions the authors investigate the dependence of patagonia s local climate precipitation and near surface air temperature year to year variability on large scale circulation anomalies using results from a 30 yr long high resolution numerical simulation variations of the low level zonal wind account for a large fraction of the rainfall variability at synoptic and interannual time scales zonal wind also controls the amplitude of the air temperature annual cycle by changi

zonally symmetric changes in the strength and position of the southern westerlies drove atmospheric co2 variations over the past 14 k y terrestrial records from 41 to 52 s across the southern hemisphere reveal nearly synchronous multimillennial trends in moisture derived from the southern westerly winds sww since 14 ka pointing to a marked zonal symmetry in sww changes across a broad swath of the southern middle latitudes the data suggest a southward shift of the sww that coincided with a rapid atmospheric co 2 rise starting ca 12 5 ka a widespread decline in sww strength between ca 10 and 7 ka contemporaneous with an 8 ppm reversal in the deglacial atmospheric co 2 rise followed by stronger sww and a steady multimillennial increase in co 2 until the preindustrial maximum we conclude that zonally symmetric changes in the intensity of the sww at multimillennial time scales have covaried with atmospheric co 2 variations since 14 ka and suggest that changes in the sww southern ocean coupled system have influenced the atmospheric co 2 concentration through wind driven upwelling of co 2 rich deep waters in the high southern latitudes