observational evidence for oceanic forcing of atmospheric variability in the nordic seas area abstractsubstantial predictability of the wintertime atmospheric variability in the nordic greenland iceland norwegian and barents seas region is reported based on oceanic observations and atmospheric reanalysis data in particular about 60 of the variance of the winter december march regional average surface air temperature sat and early winter november february zonal geostrophic winds over the western barents sea opening bso area in the period 1982 2006 is explained by the previous summer june september atlantic water temperature awt anomalies in this area the atmospheric response to oceanic heat anomalies mainly occurs in the marginal ice zone miz where the sea ice and corresponding surface heat flux shf anomalies should be triggered by entrainment of subsurface heat anomalies into the deepening mixed layer and sustained through winter by anomalous oceanic heat transport the latter should be caused by geostrophic current anomalies forced by anomalous ocean ekman suction and or on

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

arctic sea ice variability in the context of recent atmospheric circulation trends abstract forty years 1958 97 of reanalysis products and corresponding sea ice concentration data are used to document arctic sea ice variability and its association with surface air temperature sat and sea level pressure slp throughout the northern hemisphere extratropics the dominant mode of winter january march sea ice variability exhibits out of phase fluctuations between the western and eastern north atlantic together with a weaker dipole in the north pacific the time series of this mode has a high winter to winter autocorrelation 0 69 and is dominated by decadal scale variations and a longer term trend of diminishing ice cover east of greenland and increasing ice cover west of greenland associated with the dominant pattern of winter sea ice variability are large scale changes in sat and slp that closely resemble the north atlantic oscillation the associated sat and surface sensible and latent heat flux anomalies are largest over the portions of the marginal sea ice zone in which the tr

late twentieth century northern hemisphere sea ice record from u s national ice center ice charts 1 arctic sea ice plays a key role in the climate system by acting as the interface between a warm ocean and a cold atmosphere establishing the true pattern of recent behavior of the sea ice in this region is critical to simulating the role of sea ice in future climate recently released operational ice charts from the u s national ice center provide insight into the late twentieth century behavior of northern hemisphere sea ice providing more reliable ice concentrations during summer and freeze up than those available from the passive microwave record the major winter and summer modes of ice concentration variability observed from empirical orthogonal function analysis covering the period 1972 1994 are shown to indicate respectively the 1 year lagged response of the sea ice to the north atlantic oscillation and the winter preconditioning of summer sea ice coverage in the eastern arctic by the north atlantic oscillation feedback to the atmosphere is suggested in each case by zero lag cyclone frequency relationships to these two sea ice modes of variability

arctic sea ice variability on a timescale of weeks and its relation to atmospheric forcing abstract northern hemisphere sea ice concentration 500 hpa height sea level pressure and 1000 500 hpa thickness at 7 day intervals are examined for the period 1972 1989 with emphasis on the winter season the temporal variability of sea ice concentration is largest along the climatological mean ice edge where its frequency distribution is strongly bimodal with ice free and ice covered conditions being observed much more frequently than partial ice cover these results confirm impressions based on visual inspection of satellite imagery that most of the variability in these regions is associated with the advance and retreat of the ice edge relationships between large scale patterns of atmospheric variability and sea ice variability are investigated making use of singular value decomposition of the temporal covariance matrix the analysis is conducted separately for the atlantic and pacific sectors in agreement with earlier studies based upon monthly mean data on sea ice concentration the strongest

stable isotope evidence for magmatic fluid input during large scale na ca alteration in the cloncurry fe oxide cu au district nw queensland australia sodic calcic alteration is common in mineralized hydrothermal systems yet the relative importance of igneous vs basinal fluid sources remains controversial one of the most extensive volumes of sodic calcic rocks occurs near cloncurry nw queensland and was formed by overlapping hydrothermal systems that were active synchronously with emplacement of mid crustal batholithic granitoids c 1 55 1 50 ga altered rocks contain albite oligoclase actinolite diopside titanite and magnetite alteration was localized by a composite veins and breccias containing crystallized magma intimately intergrown with hydrothermal precipitates b intrusions that host setting a veins and breccias and c extensive breccia and vein systems linked to regional fault systems isotope analyses of actinolites in settings a and b indicate calculated 18oh2o 8 2 to 10 6 and variably depleted dh2o 130 to 54 compared with typical magmatic fluids whereas those from setting c typically indicate calculated 18oh2o 8 0 to 12 8 and dh2o 29 to 99 the lowest dh2o values are interpreted as representing residual fluids after significant 90 open system magmatic degassing overall the stable isotope field geochronological and geobarometric data suggest that these sodic calcic alteration systems were formed by the episodic incursion of magmatic fluids that underwent minor isotopic modification as a result of varying degrees of interaction with country rocks

the development of the odden ice tongue in the greenland sea during winter 1993 from remote sensing and field observations the odden ice tongue in the central greenland sea believed to be associated with midgyre convection developed prominently during the winter of 1993 january april during this period it was studied by a succession of cruises which formed part of the european subpolar ocean programme and which included direct sampling and measurement of the frazil and pancake ice which constituted the material of the ice tongue as well as studies of the ocean structure passive microwave imagery was used to determine the evolution of odden through the winter and when combined with ers 1 synthetic aperture radar studies and the field data yielded estimates of ice extent and thickness through the winter from these studies it was possible to estimate the salt flux into the ocean originating from brine release from sea ice during the growth phases of odden

decadal climate oscillations in the arctic a new feedback loop for atmosphere ice ocean interactions a combined complex empirical orthogonal function analysis of 40 years of annual sea ice concentration sic and winter sea level pressure slp data reveals the existence of an approximately 10 year climate cycle in the arctic and subarctic the cycle is characterized by a clockwise propagating signal in the sic anomalies and a standing oscillation in the slp anomalies the latter being linked to a fluctuation between the two phases of the north atlantic oscillation to describe the formation and evolution of the sic and slp anomalies associated with the cycle a simple feedback loop is proposed

atmospheric forcing of fram strait sea ice export a closer look fram strait is the primary region of sea ice export from the arctic and therefore plays an important role in regulating the amount of sea ice and freshwater within the arctic we investigate the variability of fram strait sea ice motion and the role of atmospheric circulation forcing using daily data during the period 1979 2006 the most prominent atmospheric driver of anomalous sea ice motion across fram strait is an east west dipole pattern of sea level pressure slp anomalies with centers of action located over the barents sea and greenland this pattern also observed in synoptic studies is associated with anomalous meridional winds across fram strait and is thus physically consistent with forcing changes in sea ice motion the association between the slp dipole pattern and fram strait ice motion is maximized at 0 lag persists year round and is strongest on time scales of 10 60 days the slp dipole pattern is the second empirical orthogonal function eof of daily slp anomalies in both winter and summer when the analysis is repeated with monthly data only the barents center of the slp dipole remains significantly correlated with fram strait sea ice motion however after removing the leading eof of monthly slp variability e g the north atlantic oscillation the full east west dipole pattern is recovered no significant slp forcing of fram strait ice motion is found in summer using monthly data even when the leading eof is removed our results highlight the importance of high frequency atmospheric variability in forcing fram strait sea ice motion

on the relationship between atmospheric circulation and the fluctuations in the sea ice extents of the bering and okhotsk seas monthly and 3 day averaged nimbus 5 electrically scanning microwave radiometer sea ice data have been analyzed to document the fluctuations of the bering sea and sea of okhotsk ice covers for the four winters 1972 1973 through 1975 1976 on the short term seasonal and interannual time scales and to define those periods for which there is an out of phase relationship between the fluctuations of the two sea ice covers the sea ice fluctuations are shown to be related to changes in the position and intensity of quasi stationary high and low pressure systems associated with large scale standing wave patterns in the atmosphere through a comparison of the areal changes in ice cover with changes in the amplitude and phase of zonal harmonics 1 2 and 3 of the sea level pressure field on the seasonal time scale the sea level pressure for december the month of most rapid seasonal sea ice growth for both the bering and okhotsk seas is dominated by harmonic 2 which explains almost 60 of the total sea level pressure variance on average over the four winters the phase of harmonic 2 which is associated with the position of the aleutian low shifts from 156 e in 1972 1973 to 190 e in 1975 1976 thus providing a connection between the increasingly heavy bering sea ice cover over these four winters and the general circulation of the atmosphere on the short term episodes of midwinter bering sea ice retreat are generally preceded by or coincident with the breakdown of harmonic 1 and the intensification of harmonics 2 and 3 these episodes are also related to the coincidence of the phases of harmonics 2 and 3 with a mean position of 165 e this result is in excellent agreement with a study of the north pacific oscillation showing that the two modes of the oscillation are associated with the longitudinal position of the aleutian low it is suggested here that these two modes result from changes in the amplitudes and phases of atmospheric long waves 1 2 and 3 evidence is also presented indicating that the interaction of standing and transient components of wave 1 may play an important role in these fluctuations finally these results establish an observational connection relating climate dynamics to changes in ice covers in seasonal sea ice zones

greenland sea odden sea ice feature intra annual and interannual variability the odden is a large sea ice feature that forms in the east greenland sea that may protrude eastward to 5 e from the main sea ice pack at about 8 w between 73 and 77 n it generally forms at the beginning of the winter season and can cover 300 000 km2 throughout the winter the outer edge of the odden may advance and retreat by several hundred kilometers on timescales of a few days to weeks satellite passive microwave observations from 1978 through 1995 provide a continuous record of the spatial and temporal variations of this extremely dynamic phenomenon aircraft synthetic aperture radar satellite passive microwave and ship observations in the odden show that the odden consists of new ice types rather than older ice types advected eastward from the main pack the 17 year record shows both strong interannual and intra annual variations in odden extent and temporal behavior for example in 1983 the odden was weak in 1984 the odden did not occur and in 1985 the odden returned late in the season an analysis of the ice area and extent time series derived from the satellite passive microwave observations along with meteorological data from the international arctic buoy program iabp determined the meteorological forcing associated with odden growth maintenance and decay the key meteorological parameters that are related to the rapid ice formation and decay associated with the odden are in order of importance air temperature wind speed and wind direction oceanographic parameters must play an important role in controlling odden formation but it is not yet possible to quantify this role because of a lack of long term oceanographic observations

stable isotope and la icp ms microanalytical evidence for a hydrothermal origin of paleoproterozoic fe oxide apatite deposits western norrbotten county sweden

greenland sea sea ice variability over 1979 2007 and its link to the surface atmosphere 1 mean winter arctic sea ice concentration based on passive microwave observations for the period 1979 2007 are analyzed to examine the variability of the western nordic seas marginal ice zone miz a principal component analysis performed on this regional domain shows that the interannual variability is dominated by a mode which captures more than 70 of the total variance and shows only moderate correlation with the leading mode of global northern hemisphere sea ice variability this mode appears to be related to a pattern of sea level pressure slp anomaly centered on the miz with large scale signature resembling the canonical pattern of the north atlantic oscillation nao still this leading mode of sic variability shows a weak temporal correlation with the nao index taking into account the intrinsic spatial asymmetry found between the two phases of the nao based on a weather regimes analysis composite sic fields are constructed which indeed suggest a preferential response of the greenland sea sic variability to negative nao like patterns of slp the slp pattern is consistent with a response of the sea ice margin to the strength of the northerly winds along eastern greenland a weak pattern of surface air temperature anomalies also emerges in the central greenland sea which occurs at least partly as a response of the surface atmosphere to sea ice concentrations changes higher order modes of winter sic variability emerge based on a shorter winter season one mode has much resemblance with the odden nordbukta pattern while another one exhibits a significant signature in the center of the greenland sea convective gyre the odden nordbukta mode shows a more symmetric relation to the nao than the leading sic mode linear regression analysis consistently suggests some link between this mode and the ice area flux through fram strait

multiple weather regimes over the north atlantic analysis of precursors and successors abstract the algorithm developed by vautard and legras is applied to a series of 37 winter of 700 mb geopotential height observations in order to identify quasi stationary patterns occurring over the extratropical north atlantic area weather regimes are obtained as solutions of a act of nine nonlinear statistical equations giving the balance of the large scale average tendency four regime patterns are found the first one exhibits the typical european blocking dipole the second one is an enhanced zonal flow the third one consists of a positive anomaly over greenland and the last one is characterized by a ridge over the eastern atlantic ocean the role played by the transient small scales in the maintenance of thew four regimes is discussed next the backward and forward memory times of the different weather regimes are established evidence is brought that the atmosphere keeps its memory of regime occurrences into the medium range 10 20 days backward memory times are shorter 5 10 days showin

the odden ice feature of the greenland sea and its association with atmospheric pressure wind and surface flux variability from reanalyses 1 the odden sea ice feature of the greenland sea is identified in a rotated principal component analysis of hadley center winter sea ice concentration data extending from 1951 2005 time series of the odden ice extent are evaluated in the context of sea level pressure surface wind air temperature cloud and energy flux variations using ncep ncar reanalyses odden was a recurring feature in winters 1966 1972 during the great salinity anomaly gsa and appeared occasionally in the 1980s and 1990s but has occurred rarely since 2000 odden formation is associated with northernmost atlantic high pressure a negative north atlantic oscillation and anomalous westerly winds its formation is most highly correlated however to air temperature and fluxes of sensible latent heat and downward longwave radiation air temperature and downward longwave flux anomalies in the preceding autumn are also unusually low in advance of a winter odden ice cover while heat fluxes are weakly positive all parameters including the ice cover anomaly exhibit significant winter to winter persistence over time

two modes of appearance of the odden ice tongue in the greenland sea the odden ice tongue of the greenland sea normally forms locally in winter as frazil pancake ice allowing for high positive salt fluxes during freezing that leads to open ocean convection we report that another type of odden can develop usually late in the season and is composed of old ice advected through the east greenland current and by the jan mayen current this type causes the introduction of more meltwater that stabilizes the water column enhances productivity and affects the carbon cycle in the region the history of oddens is reviewed and our results indicate that from 1978 through 1997 the first type occurred almost every year except in 1984 1994 and 1995 while the second type has been observed to occur in 1987 and 1996

outflow of arctic ocean sea ice into the greenland and barents seas 1979 2007 abstract twenty nine years of arctic sea ice outflow into the greenland and barents seas are summarized outflow is computed at three passages fram strait between svalbard and franz josef land s fjl and between franz josef land and severnaya zemlya fjl sz ice drift at the flux gates has been reprocessed using a consistent and updated time series of passive microwave brightness temperature and ice concentration ic fields over the record the mean annual area outflow at the fram strait is 706 113 103 km2 it was highest in 1994 95 1002 103 km2 when the north atlantic oscillation nao index was near its 29 yr peak the strength of the transpolar drift stream tds was high during the late 1980s through the mid 1990s there is no statistically significant trend in the fram strait area flux even though there is a positive trend in the gradient of cross strait sea level pressure the outflow has not increased because of a negative trend in ic seasonally the area outflow during recent sum

variability of fram strait ice flux and north atlantic oscillation we estimate the winter sea ice export through the fram strait using ice motion from satellite passive microwave data sea ice motion october may is obtained by tracking the displacement of common features in sequential 85 and 37 ghz brightness temperature fields the average winter area flux over the 18 year record 1978 1996 is 670 000 km2 7 of the area of the arctic ocean the winter area flux ranges from a minimum of 450 000 km2 in 1984 to a maximum of 906 000 km2 in 1995 the daily monthly and interannual variabilities of the ice area flux are high there is an upward trend in the ice area flux over the 18 year record the average winter volume flux over the winters of october 1990 through may 1995 is 1745 km3 ranging from a low of 1375 km3 in the 1990 flux to a high of 2791 km3 in 1994 the sea level pressure gradient across the fram strait explains more than 80 of the variance in the ice flux over the 18 year record we use the coefficients from the regression of the time series of area flux versus pressure gradient across the fram strait and ice thickness data to estimate the summer area and volume flux the average 12 month area flux and volume flux are 919 000 km2 and 2366 km3 we find a significant correlation r 0 86 between the area flux and positive phases of the north atlantic oscillation nao index over the months of december march correlation between our 5 years of volume flux estimates and the nao index gives r 0 56 during the high nao years a more intense icelandic low increases the gradient in the sea level pressure by almost 1 mbar across the fram strait thus increasing the atmospheric forcing on ice transport correlation is reduced during the negative nao years because of decreased dominance of this large scale atmospheric pattern on the sea level pressure gradient across the fram strait

moraine dam related to late quaternary glaciation in the yulong mountains southwest china and impacts on the jinsha river abstract the yulong mountain massif is tectonically active during quaternary and contains the southernmost glacierized mountains in china and all of eurasia past glacial remnants remain preserved on the east and west sides of the yulong mountains a ridge of moraine protruded into the jinsha river at the daju basin damming the river and forming a lake at the head of the jinsha river cosmogenic 10 be and 26 al provide exposure age dates for the moraine based fluvial terraces left behind after the dam breached and for moraine boulders on both the eastern and western sides of the yulong mountains our results yield exposure ages for the terraces that range from 29 ka to 8 ka and a downcutting rate of 7 6 m ka the preservation of the remaining dam for over 10 000 years suggests stability of the moraine dam and gradual erosion of the dam during drainage of the dammed lake from the relationship between exposure ages and elevations of the fluvial terraces located in different walls of the daju fault we obtain a late quaternary dip slip rate of about 5 6 m ka for the daju fault the exposure ages of 10 2 ka and 47 ka for moraine boulders located in the east and west sides of the yulong mountains respectively coincide with warm periods in the late quaternary this implies that precipitation provides the major control for glaciations on the yulong mountains a domain of the southwest asian monsoon

evidence for a recent change in the link between the north atlantic oscillation and arctic sea ice export evidence for a recent change in the link between the north atlantic oscillation nao and arctic sea ice export through fram strait during wintertime djfm is presented from the analysis of simulated arctic sea ice and observations for the period 1958 1997 whereas no correlation between the two time series is found from 1958 to 1977 r 0 1 the correlation increased significantly thereafter r 0 7 1978 1997 the increased coherency between the nao and arctic sea ice export through fram strait during the last two decades resulted from anomalous meridional wind components near fram strait which were associated with the more easterly position of the nao s centers of interannual variability compared to 1958 1977

scaling factors for the rates of production of cosmogenic nuclides for geometric shielding and attenuation at depth on sloped surfaces abstract the decrease in rates of production of cosmogenic nuclides occurs because of shielding of cosmic rays by mountains sloped surfaces and local rock formations that block them when a large part of the sky is blocked this correction is large and requires detailed model calculations this paper considers three geometries a rectangular obstruction a triangular obstruction and a sloped surface other geometries can be considered as a combination of these the results are presented in terms of formulas and graphs so that the reader can easily apply them to common field situations any use of cosmogenic nuclides in the study of geomorphic processes or forms must consider factors that introduce variations in the production of nuclides

magmatic hydrothermal albite actinolite apatite rich rocks from the cloncurry district nw queensland australia abstract albite quartz actinolite apatite rich rocks with accessory titanite form a carapace that caps a small dome like intrusion of roxmere pluton and provide evidence of the accumulation and release of magmatic fluids that may have contributed to regionally extensive na ca alteration in the proterozoic cloncurry district australia the roxmere pluton was emplaced after the peak amphibolite facies metamorphism and into psammitic metasedimentary rocks that are stratigraphically younger and overlie the calc silicate rich mary kathleen group na ca hydrothermal assemblages closely spatially related to the roxmere pluton suggest that na ca alteration in this case is inconsistent with excepted up temperature metamorphic fluid circulation models the carapace rocks comprise two variants aplite and pegmatite both of which were affected by alteration and brecciation aplitic material predominates and the carapace has a brecciated top and a distinct textural zonation from an aplite rich pegmatite poor base to a relatively aplite poor pegmatite rich top this zonation is interpreted to represent the progressive accumulation of volatile phases toward the top of the carapace which culminated in fluid overpressuring and brecciation of the granitoid stock the convoluted and ptygmatic habit of the aplitic and pegmatitic material within the carapace is similar in nature to the comb quartz unidirectional solidification textures that are developed in the roof zones of some porphyry stocks these complex textures are interpreted to have formed from a single phase of fluid saturation the roxmere pluton or a deeper equivalent has a na mg and ca rich composition and a clinopyroxene amphibole rich mineralogy that is consistent with the formation of the contained albite actinolite apatite rich phases however the source of the rocks within the carapace is equivocal given that their contact relationships are obscured the 18 o composition of minerals within the carapace has the following ranges albite 7 1 8 7 actinolite 8 0 8 5 and quartz 8 9 11 4 albite and quartz 18 o equilibria suggest that these minerals in the pegmatitic and aplitic components formed at temperatures of 510 c to 540 c the calculated 18 o composition of a fluid in equilibrium with these minerals 6 0 to 8 0 at temperatures between 450 c and 550 c is consistent with a magmatic origin these estimated temperatures and 18 o fluid composition are comparable to estimates for regional na ca alteration in contrast d analysis of actinolite 136 to 150 within the carapace demonstrates that these fluids have a significantly lower d signature compared to na ca alteration assemblages associated with regional alteration 70 to 90 the low values in the carapace could either be interpreted as being produced from meteoric fluids or from degassed magmatic fluids although a meteoric fluid model is deemed improbable as meteoric fluids in the district have a documented d composition of ca 0 0 as a consequence an open system degassed magmatic hydrothermal fluid origin is considered to be the most plausible explanation for the low isotopic signatures and is also consistent with the complex textural relationships described within the carapace

long term coordinated changes in the convective activity of the north atlantic the north atlantic is a peculiarly convective ocean the convective renewal of intermediate and deep waters in the labrador sea and greenland iceland sea both contribute significantly to the production and export of north atlantic deep water thus helping to drive the global thermohaline circulation while the formation and spreading of 18 degree water at shallow to intermediate depths off the us eastern seaboard is a major element in the circulation and hydrographic character of the west atlantic for as long as time series of adequate precision have been available to us it has been apparent that the intensity of convection at each of these sites and the hydrographic character of their products have been subject to major interannual change as shown by aagaard 1968 clarke et al 1990 and meincke et al 1992 for the greenland sea in the ows bravo record from the labrador sea eg lazier 1980 et seq and at the panulirus hydrostation s site in the northern sargasso off bermuda eg jenkins 1982 talley and raymer 1982 this paper reviews the recent history of these changes showing that the major convective centres of the greenland and labrador seas are currently at opposite convective extrema in our postwar record with vertical exchange at the former site limited to 1000 m or so but with labrador sea convection reaching deeper than previously observed to over 2300 m as a result greenland sea deep water has become progressively warmer and more saline since the early 70 s due to increased horizontal exchange with the arctic ocean through fram strait while the labrador sea water has become progressively colder and fresher over the same period through increased vertical exchange most recently convection has become deep enough there to reach into the more saline nadw which underlies it so that cooler but now saltier and denser lsw has resulted

wind feedback mediated by sea ice in the nordic seas air sea interactions play a critical role in the climate system this study investigates wind induced changes in the ocean surface temperature and sea ice cover feeding back onto the atmospheric circulation this interaction was modeled in the nordic seas using a partial coupling method to constrain the ocean with prescribed wind forcing in an otherwise fully coupled earth system model this enabled the evaluation of not only the direct oceanic but also the indirect atmospheric response to idealized forcing scenarios of perturbed winds over the nordic seas the results show that an anticyclonic wind anomaly forcing leads to significant surface cooling in the greenland sea mostly due to anomalous drift of sea ice during winter the cooling reduces the net surface heat flux to the atmosphere and increases sea level pressure the pressure gradients result in anomalous geostrophic southerly winds which locally are comparable both in direction and in velocity to the prescribed forcing anomalies suggesting a positive feedback

atmospheric influence on arctic marginal ice zone position and width in the atlantic sector february april 1979 2010 arctic marginal ice zone miz widths in the atlantic sector were measured during the months of maximum sea ice extent february april for years 1979 2010 using a novel method based on objective curves through idealized sea ice concentration fields that satisfied laplace s equation over the record the labrador sea miz mizl had an average width of 122 km and narrowed by 28 while moving 254 km poleward the greenland sea miz mizg had an average width of 98 km and narrowed by 43 while moving 158 km west toward the greenland coast and the barents sea miz mizb had an average width of 136 km and moved 259 km east toward the eurasian coast without a trend in width trends in miz position and width were consistent with a warming arctic and decreasing sea ice concentrations over the record beyond the trends nao like atmospheric patterns influenced interannual variability in miz position and width mizl widened and moved southeast under anomalously strong northerly flow conducive to advection of sea ice into the labrador sea mizg widened and moved northeast under anomalously weak northerly flow conducive to diminishing the westward component of sea ice drift and mizb widened and moved poleward at the expense of pack ice under anomalously strong southwesterly flow conducive to enhancing oceanic heat flux into the barents sea in addition meridional flow anomalies associated with the nao per se moved mizb east and west by modulating sea ice concentration over the barents sea

erosion in northwest tibet fromin situ produced cosmogenic10be and26al in bedrock concentrations of in situ produced cosmogenic nuclides 10be and 26al in quartz were measured by accelerator mass spectrometry for bedrock basalts and sandstones located in northwest tibet the effective exposure ages range between 23 and 134 ka 10be and erosion rates between 4 0 and 24 mm ka 1 the erosion rates are significantly higher than those in similarly arid antarctica and australia ranging between 0 1 and 1 mm ka 1 suggesting that precipitation is not the major control of erosion of landforms comparison of erosion rates in arid regions with contrasting tectonic activities suggests that tectonic activity plays a more important role in controlling long term erosion rates the obtained erosion rates are however significantly lower than the denudation rate of 3000 6000 mm ka 1 beginning at c 5 3 ma in the nearby godwin austen k2 determined by apatite fission track thermochronology it appears that the difference in erosion rates within different time intervals is indicative of increased tectonic activity at c 5 3 ma in northwest tibet we explain the low erosion rates determined in this study as reflecting reduced tectonic activity in the last million years a model of localized thinning of the mantle beneath northwest tibet may account for the sudden increased tectonic activity at c 5 3 ma and the later decrease copyright 2006 john wiley sons ltd

dip slip rate determined by cosmogenic surface dating on a holocene scarp of the daju fault yunnan china abstract the daju and lijiang daju fault zones which bound the yulong mountains on its northern and eastern perimeters respectively are segments of a continuous fault system that bends at daju uplift of the yulong mountains the southernmost glacierized mountain range in eurasia resulted from the normal faulting characteristics of the fault system using cosmogenic surface exposure dating with 10 be and 26 al we have measured bedrock exposure ages as a function of elevation along an exposed bedrock scarp of the daju fault 10 be and 26 al exposure ages increase monotonically with elevation ranging from 2 6 to 9 6 ka over the 51 m scarp length giving an average dip slip rate of 7 5 m ka during the holocene period and a vertical uplift rate of 5 7 m ka the 5 7 m ka holocene uplift rate and supporting geomorphic features suggest that the uplift of the yulong mountains mainly occurred in the quaternary the fast slip rate and seismic quiescence for the recent 2 8 ka call attention to the possible recurrence of large magnitude earthquake events along the fault zone

fram strait sea ice outflow 1 we summarize 24 years 1978 2002 of ice export estimates and examine over a 9 year record the associated variability in the time varying upward looking sonar uls thickness distributions of the fram strait a more thorough assessment of the pmw passive microwave ice motion with 5 years of synthetic aperture radar sar observations shows the uncertainties to be consistent with that found by kwok and rothrock 1999 giving greater confidence to the record of ice flux calculations interesting details of the cross strait motion profiles and ice cover characteristics revealed by high resolution sar imagery are discussed the average annual ice area flux over the period is 866 000 km2 yr between the 1980s and 1990s the decadal difference in the net exported ice area is 400 000 km2 approximately half the annual average except for the years with extreme negative nao correlation of winter ice area export with the nao index remains high r2 0 62 with thickness estimates from uls moorings we estimate the average annual ice volume flux 8 years to be 2218 km3 yr 0 07 sv over the 9 year uls ice thickness data set there is an overall decrease of 0 45 m in the mean ice thickness over the entire time series and a decrease of 0 23 m over the winter months december through march correspondingly the mode of the my ice thickness exhibits an overall decrease of 0 55 m and a winter decrease of 0 42 m these are significant trends whether these trends are indicative of the thickness trends of the arctic ocean is examined as the time varying behavior of the monthly uls thickness distributions can be related not only to the seasonal cycle in the basal growth and melt but also to the magnitude and pattern of ice motion in the arctic ocean and the proximity of the uls moorings to the ice edge

forcing of oceanic heat anomalies by air sea interactions in the nordic seas area 1 hydrographic data and atmospheric reanalysis from 1982 to 2005 are used to show a strong link of the atlantic water temperature awt anomalies observed in the transition zone between the norwegian atlantic current and the west spitsbergen current in summer to the surface heat flux shf anomalies observed over the barents sea open water in the preceding late winter a mechanism proposed for this link is formation of ocean temperature anomalies in a deep mixed layer and their subsequent westward export by a branch of atlantic water recirculating in the western barents sea the shf anomalies over the barents sea are due to advection of temperature and humidity by anomalous winds across the arctic ice edge and do not strongly depend on the north atlantic oscillation nao correlations of up to about 0 9 between the awt anomalies and indices of atmospheric variability over the barents sea open prospects for seasonal awt predictability it is also shown that the wind forcing responsible for positive awt anomalies is involved in a cyclonic perturbation of the atmospheric circulation over the nordic seas this perturbation generates through influence on the sea ice distribution a lobe of shf anomalies in the marginal ice zone miz on the eastern barents sea and western greenland sea sides of the nordic seas which has the opposite sign to the open water lobe in contrast to the barents sea miz the diabatic heating of the atmosphere by upward shf anomalies in the greenland sea miz competes with cold advection