retrieving forest background reflectance in a boreal region from multi angle imaging spectroradiometer misr data studies of the bidirectional behavior of forest canopy have shown that the total reflectance of a forest canopy is the combination of illuminated and shaded components of the tree crown as well as the background in this study we estimate the background portion from the bidirectional reflection observed by multi angle imaging spectroradiometer misr instrument which scans the earth in nine different view angles in an oblique plane relative to the sun the nadir and 60 forward directions of the misr images were used to derive the reflectivity of the forest background based on the probabilities of viewing the illuminated tree crown and background on those view angles the probabilities were estimated using the four scale model in the study background reflectivity mosaic images in red and nir wavelengths covering the boreas region during winter and spring seasons were obtained the mosaic images of winter show high background reflectivity in both wavelengths and in most of the areas the reflectivity was more than 0 3 in mosaic images of spring the spatial variations in the background reflectivity were considerable the seasonal changes in the background reflectivity were also studied with multi temporal misr data and a similarity in the temporal pattern was found between the retrieved forest background reflectivity and grass land reflectance these spatial and temporal patterns of the background component retrieved from misr would be critically important in retrieving the biophysical parameters of vegetation and in ecosystem modeling

the impact of abrupt deglacial climate variability on productivity and upwelling on the southwestern iberian margin abstract this study combines high resolution records of nannofossil abundances oxygen and carbon stable isotopes core scanning x ray fluorescence xrf and ice rafted debris ird to assess the paleoceanographic changes that occurred during the last deglaciation on the sw iberian margin our results reveal parallel centennial scale oscillations in coccolithophore productivity nutricline depth and upwelling phenomena not previously observed explained by means of arrival of iceberg melting waters iceberg induced turbulent conditions sst changes and riverine discharges on millennial time scales higher primary productivity pp shallower nutricline and upwelling occurrence invigoration are observed for the last glacial maximum lgm and bolling allerod b a the opposite scenario i e lower productivity deeper nutricline and upwelling weakening absence is linked to cold spells such as heinrich stadials 2 and 1 hs2 and hs1 and the younger dryas yd such paleoproductivity variations are attributed to latitudinal migrations of the thermal fronts associated with oceanic gyres in the north atlantic in parallel to oscillations in the strength of the atlantic meridional overturning circulation amoc moderate to high pp during the holocene is ascribed to the development of the modern seasonal surface hydrography with a more persistent iberian poleward current ipc and seasonal wind induced upwelling

holocene interdependences of changes in sea surface temperature productivity and fluvial inputs in the iberian continental shelf tagus mud patch 1 sea surface temperature sst marine productivity and fluvial input have been reconstructed for the last 11 5 calendar cal ka b p using a high resolution study of c37 alkenones coccolithophores iron content and higher plant n alkanes and n alkan 1 ols in sedimentary sequences from the inner shelf off the tagus river estuary in the portuguese margin the sst record is marked by a continuous decrease from 19 c at 10 5 and 7 ka to 15 c at present this trend is interrupted by a fall from 18 c during the roman and medieval warm periods to 16 c in the little ice age river input was very low in the early holocene but increased in the last 3 cal ka b p in association with an intensification of agriculture and deforestation and possibly the onset of the north atlantic oscillation atlantic multidecadal oscillation modes of variability river influence must have reinforced the marine cooling trend relative to the lower amplitude in similar latitude sites of the eastern atlantic the total concentration of alkenones reflects river induced productivity being low in the early holocene but increasing as river input became more important rapid cooling of 1 2 c occurring in 250 years is observed at 11 1 10 6 8 2 6 9 and 5 4 cal ka b p the estimated age of these events matches the ages of equivalent episodes common in the ne atlantic mediterranean region this synchronicity reveals a common widespread climate feature which considering the twentieth century analog between colder ssts and negative north atlantic oscillation nao is likely to reflect periods of strong negative nao

position of the polar front along the western iberian margin during key cold episodes of the last 45 ka 1 this paper documents the migration of the polar front pf over the iberian margin during some of the cold climatic extremes of the last 45 ka it is based on a compilation of robust and coherent paleohydrological proxies obtained from eleven cores distributed between 36 and 42 n planktonic 18o globigerina bulloides ice rafted detritus concentrations and the relative abundance of the polar foraminifera neogloboquadrina pachyderma sinistral were used to track the pf position these three data sets compared from core to core show a consistent evolution of the sea surface paleohydrology along the iberian margin over the last 45 ka we focused on five time slices representative of cold periods under distinct paleoenvironmental forcings the 8 2 ka event and the younger dryas two recent cold events occurring within high values of summer insolation heinrich events 1 and 4 reflecting major episodes of massive iceberg discharges into the north atlantic and the last glacial maximum typifying the highest ice volume accumulated in the northern hemisphere for each event we generated schematic maps mirroring past sea surface hydrological conditions the maps revealed that the polar front presence along the iberian margin was restricted to heinrich events the sea surface conditions during the last glacial maximum were close to those at present day except for the northern sites which briefly experienced subarctic conditions

g function and hot spot ghost reflectance model application to multi scale airborne polder measurements abstract the complex architecture of conifer species affects the radiation scattering processes that influence the bidirectional reflectance distribution function brdf characteristics an interesting brdf signature is the hot spot effect that yields a maximum of reflectance in the sun direction it has been shown that the hot spot phenomenon is sensitive to the foliage structure the present work introduces the g function and hot spot ghost model that simulates the brdf of boreal forest in accounting for the arrangement and the structure of the stems the model represents the medium by a distribution of conical crowns whose size and shape are accounted for in the g function expression ghost compares quite well with airborne polarization and directionality of earth reflectances polder reflectances acquired during the boreas experiment at various scale resolutions ranging from 2 helicopter up to 35 m aircraft the inversion procedure exploits the multidirectionality of measurements with emphasis on the hot spot observations and the angular range of dominant influence of each parameter the retrieved parameters translate optical and structural properties of the canopy they are used to calculate a new architectural parameter x that allows to get the clumping index of the patch vegetation

multi angular reflectance properties of a hemiboreal forest an analysis using chris proba data abstract forest types differ in their hyperspectral anisotropy patterns mainly due to species specific geometrical structure spatial arrangement of canopies and subsequent shadow patterns this paper examines the multi angular hyperspectral reflectance properties of typical hemiboreal forests during summer time using three simultaneous chris proba mode 3 scenes and stand inventory data from the jarvselja training and experimental forestry district in southeastern estonia we investigated the magnitude and reasons for the differences in the anisotropy patterns of deciduous and coniferous stands at three backward viewing angles a forest reflectance model frt was used as a tool to provide a theoretical basis to the discussion and to estimate the directional contribution of scattering from crowns and ground to total stand reflectance for the two forest types the frt model simulated successfully the hdrf hemispherical directional reflectance factor curves of the study stands to match those obtained from the chris image yet it produced a smaller and less wavelength dependent angular reflectance effect than was observed in the satellite image the main results of this study provide new information for separating the spectral contribution of the forest floor or understory layer from the tree canopy layer 1 the red edge domain was identified to have the largest contribution from forest understory and 2 the more oblique the viewing angle the smaller the contribution from the understory in addition coniferous stands were observed to have a specific angular effect at the red and red edge domain possibly as a result of the hierarchical structure and arrangement of coniferous canopies

variability of biome reflectance directional signatures as seen by polder reflectance measurements acquired with the spaceborne polder instrument are used to analyze the variability of land surface directional signatures as a function of vegetation cover type the reflectance directional signatures are quantified by the three parameters of a modified version of the ross li reflectance model the variability of the estimated parameters with respect to the seven modis biome classes was found to be higher within the classes than between classes with the exception of the desert targets that show more isotropic reflectances a limited number of standard brdfs typically 5 in the red and near infrared capture most of the variability of the directional reflectance measurements supporting the idea that different land surfaces have similar directional signatures over vegetation targets they are characterized by a strong increase toward backscattering and much smaller variations in forward directions the results express the diversity in structural situations within a given biome class and indicate that at the resolution of the polder sensor i e a few kilometers the brdf contains little information on the dominant vegetation type we show that standard directional signatures may be used to correct the reflectance measurements for directional effects with an rms error on the order of 0 011 in the red and 0 015 in the near infrared

primary productivity response to heinrich events in the north atlantic ocean and norwegian sea 1 the last glacial was punctuated by several massive ice sheet surges into the north atlantic that impacted surface water hydrology especially where icebergs melted however the links between variations in surface water hydrology and surface water productivity during these heinrich events hes remain uncertain to address this issue diatoms and organic carbon were examined across heinrich event 1 he 1 and heinrich event 4 he 4 in seven sediment cores spanning 40 n to 63 n latitude our results show low diatom abundances during hes consistent with decreased surface water productivity diatom dilution by increased sediment flux was tested by normalizing diatom abundance to a constant 230th flux although the particle rain rate was enhanced during hes this does not explain the sharp drop in diatoms during he 4 surface productivity decreased at all latitudes examined probably because of strong year round stratification the same inferred changes occurred during he 1 within the area of maximum iceberg melting however at northern latitudes above 50 n the summer insolation increase of the glacial termination drove increased surface productivity during the whole period including he 1 marine organic carbon taken as independent proxy for export production supports the diatom data trends shown by the productivity proxies evolve generally in parallel with the hydrographic proxies with an increase in productivity when sea surface temperature increases

characterization of surface heterogeneity detected at the misr terra subpixel scale vegetation structure can have a significant impact on the degree of anisotropy in the reflected radiation field with the appropriate characterization of these effects the analysis of multiangular data such as provided by the multi angle imaging spectroradiometer misr instrument on board terra can yield statistical information about the type of surface heterogeneity that exists at the subpixel scale

hydrographic conditions along the western iberian margin during marine isotope stage 2 the surface water hydrography along the western iberian margin as part of the north atlantic s eastern boundary upwelling system consists of a complex seasonally variable system of equatorward and poleward surface and subsurface currents and seasonal upwelling not much information exists to ascertain if the modern current and productivity patterns subsisted under glacial climate conditions such as during marine isotope stage mis 2 and how north atlantic meltwater events especially heinrich events affected them to help answer these questions we are combining stable isotope records of surface to subsurface dwelling planktonic foraminifer species with sea surface temperature and export productivity data for four cores distributed along the western and southwestern iberian margin md95 2040 md95 2041 md99 2336 and md99 2339 the records reveals that with the exception of the heinrich events and greenland stadial gs 4 hydrographic conditions along the western iberian margin were not much different from the present during the last glacial maximum lgm subtropical surface and subsurface waters penetrated poleward to at least 40 6 n site md95 2040 export productivity was in general high on the western margin during the lgm and low in the central gulf of cadiz in agreement with the modern situation during the heinrich events and gs 4 on the other hand productivity was high in the gulf of cadiz and suppressed in the upwelling regions along the western margin where a strong halocline inhibited upwelling heinrich event 1 had the strongest impact on the hydrography and productivity off iberia and was the only period when subarctic surface waters were recorded in the central gulf of cadiz south of lisbon 39 n the impact of the other heinrich events was diminished and not all of them led to a significant cooling in the surface waters thus climatic impacts of heinrich events highly varied with latitude and the prevailing hydrographic conditions in this region

abrupt variability of the last 24 ka bp recorded by coccolithophore assemblages off the iberian margin core md03 2699 a high resolution coccolithophore study allowed reconstructing sea surface conditions during the last 24 ka bp off the iberian margin variations in nannoplankton accumulation rate cold water species florisphaera profunda umbilicosphaera sibogae and coccolithus pelagicus ssp azorinus trends suggest the occurrence of substantial changes in surface water dynamics palaeoproductivity shows changes during the glacial and the interglacial transition from intense glacial upwelling to persistent interglacial stratification a drastic productivity decline occurred between 18 and 13 ka bp related to the arrival of subpolar waters indicated by the presence of the subarctic subspecies c pelagicus pelagicus and increased percentages of tetra unsaturated alkenones abrupt variability at core md03 2699 during the last 24 ka bp was observed in palaeoproductivity and sea surface temperatures proxies increases of reworked species fluxes were observed during the last glacial maximum and during the transition to the holocene likely connected to turbidity currents and or contourites formed by mediterranean outflow intensification in addition c pelagicus ssp pelagicus presence gephyrocapsa muellerae and tetra alkenone percentages reveal rapid coolings coeval with the holocene bond cycles and rapid climate coolings recognized for the northern hemisphere between 11 02 and 1 7 ka bp and associated with subpolar water arrival at the site copyright 2013 john wiley sons ltd

hydraulic and sedimentological characterizations of a reach on the anaktuvuk river alaska rivers located on the north slope of alaska s brooks range are typically not well characterized with respect to basic hydraulic and sedimentological data in order to obtain basic hydrosedimentological information on the anaktuvuk river a pristine stream located in the colville river basin we conducted an extensive field campaign from late may to early june 2009 the study reach was located at n69 27 78 5 w151 09 85 8 latitude and longitude respectively the anaktuvuk river flows north from the brooks range to the colville river drains an area of 7 058 km2 and encompasses 2 063 m of vertical relief during the field campaign the field crew measured discharge and water surface slope collected water samples and characterized bed sediment as a result of fieldwork and laboratory work we present an initial rating curve for the anaktuvuk river as well as the calculated roughness coefficient and suspended sediment concentrations in addition we compare the observed bankfull discharges with th

enhanced discrimination of boreal forest covers with directional reflectances from the airborne polarization and directionality of earth reflectances polder instrument during the boreal ecosystem atmosphere study boreas directional and spectral reflectance measurements were acquired from may to july 1994 with the polarization and directionality of earth reflectances polder instrument on board a nasa c 130 aircraft the instrument has a wide field of view optics a two dimensional ccd array and a rotating wheel carrying filters in the visible and near infrared measurements were obtained 1 over coniferous forests at the young and old jack pine and old black spruce sites 2 over a deciduous forest at the old aspen site and 3 over a fen at the fen site a prominent hot spot feature was apparent at each site with an additional strong peak in the specular direction for the fen site strong variations of the bidirectional reflectance distribution function brdf with sun zenith angle were observed for a constant sun zenith angle the variation of the brdf of conifer stands between may and july was relatively weak a key objective of this paper is to quantify the improvement of discrimination of various forest covers when remotely sensed directional signatures are added to the more conventional spectral signatures the experimental protocol consisted of the following steps first 150 pixels pertaining to five different classes of forest covers were selected on land cover maps available in the boreas information system boris data base second the brdf measurements acquired by polder at each pixel were adjusted against a three parameter semiempirical brdf model and processed to retrieve the reflectance seen in three different viewing directions third the results of supervised classifications were compared on all selected pixels using as input either the reflectances in only one direction this simulates the case of conventional spectral signatures or reflectances acquired in three directions this simulates the case of spectral directional signatures the results showed that when only one spectral band was used the proportion of correctly classified pixels increased from 36 59 with one viewing direction to 64 84 with three viewing directions when three spectral bands were considered this proportion improved from 72 87 to 83 97 these results demonstrate that the account of directional information enhances the ability to discriminate forest covers by remotesensing

climate variability across the last deglaciation in nw iberia and its margin abstract the direct comparison between marine and terrestrial data from the nw iberian margin core md03 2697 allows us to accurately evaluate without chronological ambiguity the vegetation response to north atlantic climate events across the last deglaciation comparison of md03 2697 data with other marine and terrestrial records from a vast area stretching from the azores to western w france iberia and its margin the w mediterranean and nw africa reveals the importance of enhanced winter north atlantic westerlies episodes in driving a heterogeneous regional climatic signal during particular events of the last deglaciation heinrich stadial 1 hs1 oldest dryas is a complex event marked by three synchronous main phases a extremely cold relatively wet b cool dry c relatively warmer increasing moisture availability in regions directly influenced by the north atlantic while it is characterized by a single phase cold and dry in most inland and high altitude areas changes in the strength and position of north atlantic westerlies could explain the variability in moisture during hs1 from w pyrenees to w mediterranean the bolling allerod b a event is marked by a synchronous progressive increase of ocean and atmospheric temperatures and precipitation from the bolling to the allerod in w iberia and w pyrenees contrasting with the greenland temperature pattern mid to high latitudes thermal contrast and the gradual strengthening of the atlantic meridional overturning circulation amoc triggered the continuing enhancement of westerlies and moisture along this period finally the younger dryas yd stadial is characterized by a land ocean synchronous returning cold conditions but not so cold as hs1 and although dry conditions persisted during this period extreme winter precipitation occurrences might have affected the most coastal areas of north and central w iberia and pyrenees in contrast dry conditions persisted during the yd in the western mediterranean regions the westerlies migrated further north following the displacement of the polar front during the deglaciation precluding the input of moisture in the w mediterranean region which persisted very dry during the yd stadial

past circulation along the western iberian margin a time slice vision from the last glacial to the holocene abstract fifteen iberian margin sediment cores distributed between 43 12 n and 35 53 n have been used to reconstruct spatial and temporal sub surface circulation along the iberian margin since the last glacial period time slice maps of planktonic foraminiferal derived summer sea surface temperature sst and export productivity pexp were established for specific time intervals within the last 35 ky the holocene recent and last 8 ky younger dryas yd heinrich stadials hs 1 2a 2b 3 and the last glacial maximum lgm the sst during the holocene shows the same latitudinal gradient along the western iberian margin as present day with cold but productive areas that reflect the influence of coastal upwelling centers the lgm appears as a slightly less warm but more productive period relative to the holocene and present day conditions suggesting that sea level minima forced a westward displacement of the coastal upwelling centers possibly accompanied by a strengthening of northward winds during the yd a longitudinal thermal front is depicted at 10 w with cold polar waters offshore and warmer subtropical waters inshore suggesting that the subtropical paleo iberian poleward current more likely flowed at a more inshore location masking the local sst signal and amplitude of variation a substantial cooling and drop in productivity is observed during all hs in particular hs1 and hs3 reflecting the penetration of icebergs derived meltwater these most extreme southward extensions of very cold waters define a strong sst gradient that marks a possible paleo azores front higher production south of this front was likely fed by frontal nutrient advection

coccolithophore paleoproductivity and ecology response to deglacial and holocene changes in the azores current system 1 in order to test the sensitivity of marine primary productivity in the midlatitude open ocean north atlantic to changes in the atlantic meridional overturning circulation amoc we investigated two spliced sediment cores from a site south of the azores islands at the northern rim of the north atlantic subtropical gyre for this purpose we analyzed coccolithophore assemblages diatom abundances alkenones and conducted x ray fluorescence xrf core scanning during times of reduced amoc especially during heinrich event 1 h1 and the younger dryas we observe a strong increase in productivity as evidenced by high coccolith accumulation rates high alkenone concentrations accumulation rates high ba ti ratios high abundances of diatoms and low abundances off profunda the increased productivity is partly caused by a more southern position of the azores front azf and hence by a less northward extension of the subtropical gyre as deduced from high abundances of the temperate coccolithophore species g muellerae and low abundances of subtropical species oolithotus spp umbellosphaera spp umbilicosphaeraspp however to explain the full range of the observed productivity increase other factors like increased westerly winds and advection of nutrient rich surface waters have also to be considered because this pattern can also be observed in other sediment cores from the midlatitude north atlantic we propose that during times of reduced amoc there has been a band of strongly increased productivity across the north atlantic at the northern rim of the contracted subtropical gyre which partly counteracts the decreased organic carbon pump in the high northern latitudes

response of the subtropical north atlantic surface hydrography on deglacial and holocene amoc changes the north atlantic subtropical gyre stg circulates warm waters between 10 and 40 degrees n and is a potential area of heat storage during periods of reduced north atlantic meridional overturning circulation amoc when warm salt rich waters are retained in the subtropics in this study we investigated multicentennial to millennial scale changes in subtropical north atlantic hydrography in response to amoc changes during the last deglaciation and early holocene using sediment cores md08 3180 and geofar kf16 the coring site 38 degrees n is situated near the boundary between transitional eastern north atlantic waters and stg waters that is formed by the azores front hydrographic changes are reconstructed using new stable isotope data of benthic and subsurface dwelling planktonic foraminifera mg ca measurements on planktonic foraminifera and planktonic foraminifera abundances that are supplemented with published sea surface temperature and stable isotope data these multiproxy data indicate a close coupling between the latitudinal position of the northern stg boundary and deglacial amoc modes during weak amoc phases heinrich event 1 younger dryas yd 8 2ka event northern hemisphere subpolar water reached down to the northern stg boundary displacing the boundary southward during the bolling allerod warm period a strong warming trend of the subtropical region to 19 degrees c is observed a cooling of the sea surface temperature by 6 degrees c during the yd is accompanied by ongoing northward transport of warm subsurface water that might have contributed to the restart of amoc

the effect of crown shape on the reflectance of coniferous stands abstract the kuusk nilson forest reflectance model was used to study the effect of crown shape on the reflectance of scots pine and norway spruce stands in the first part of the study we examined spruce and pine stands with an age range of 20 100 years and compared their simulated hemispherical directional reflectance factors hdrfs at nadir in red 661 nm nir 838 nm and mir 1677 nm when crowns were modeled as ellipsoids or cones in all the cases when a stand was modeled with conical crowns it had a smaller reflectance factor than the same stand with ellipsoidal crowns to analyze the sensitivity of hdrf on crown shape in the second part of the study we simulated the angular distributions of hdrf of two pine stands with different leaf area index lai and canopy closure values at 661 nm assuming four different crown shapes cone cylinder ellipsoid and cylinder bottom cone top and separated the components forming the hdrf considerable difference in the hdrf between the four crown shapes was observed the larger the crown volume the higher the canopy reflectance at similar lai and canopy closure a comparison of the two stands revealed that in denser stands with a higher canopy closure single scattering from tree crowns was responsible for the difference in hdrf between the different crown shapes whereas in stands with a smaller canopy closure the single scattering from ground dominated the hdrf finally the role of crown shape for the retrieval of lai by inversion from remotely sensed data is discussed

uniqueness of multiangular measurements i an indicator of subpixel surface heterogeneity from misr the recent availability of quasi simultaneous multispectral and multidirectional measurements from space as provided by the multi angle imaging spectroradiometer misr on board the terra platform offers new and unique opportunities to document the anisotropy of land surfaces at critical solar wavelengths this paper presents simple physical principles supporting the interpretation of the anisotropy of spectral radiances exiting terrestrial surfaces in terms of a signature of surface heterogeneity the shape of the anisotropy function is represented with two model parameter values which may be mapped and interpreted in their own right the value of one of these parameters also permits identifying geophysical conditions where the surface heterogeneity becomes significant and where three dimensional 3d radiation transfer effects have to be explicitly accounted for this paper documents these findings on the basis of results from a number of 3d radiation transfer model simulations the latter are used to perform an extensive sensitivity study which includes issues related to the scale of investigation a preliminary validation of these results conducted with a dataset collected by the airmisr instrument over the konza prairie is also discussed

geometric optical bidirectional reflectance modeling of a conifer forest canopy a geometric optical forest canopy model that treats conifers as cones casting shadows on a contrasting background explains the major anisotropies in bidirectional reflectance measurements of a conifer forest canopy taken from the literature the model uses parallelray geometry to describe the illumination and viewing of conifers as three dimensional cones cones are randomly placed and overlap freely cone size height is distributed lognormally and cone form described by the apex angle of the cone is a negative exponential function of height the cones are first presumed to be solid dark gray lambertian objects located on a lighter gray lambertian background to add realism translucence is added and light is allowed to pass through cones with negative exponential attenuation both computer simulation and analytical closed form expressions are implemented the results show a good qualitative agreement with the directional reflectance measurements of the conifer stand indicating that the three dimensional nature of the canopy is a key factor in determining its directional reflectance

coccolithus pelagicus a productivity proxy related to moderate fronts off western iberia abstract the traditional interpretation of coccolithus pelagicus as a cold water proxy is examined based on its distribution patterns in the water column off the portuguese coast using data from eleven cruises and in holocene surface sediment samples and quaternary cores from the same region coccolithus pelagicus is common in the portuguese upwelling system an area where surface waters are predominantly of subtropical origin although revealing an affinity for low temperature upwelled waters the species was found in waters up to 18 c associated with riverine plume and shelf break fronts c pelagicus seemed to consistently occupy a particular ecological niche between other phytoplankton groups related to moderate turbulence conditions combined with nutrient availability from this behaviour it is proposed that c pelagicus can be used as a tracer of the periphery of areas of enhanced productivity coccolithus pelagicus preferences for fronts of moderate temperature and salinity gradients are tentatively used to explain particular features of its sedimentary record the repeated increase of c pelagicus in thanatocoenoses surface sediment assemblages close to three river mouths on the portuguese shelf are interpreted as a positive response to the development of riverine plumes on the other hand inconsistencies in the correlation between sea surface cooler glacial and warmer interglacial isotope stages and the relative abundance pattern of c pelagicus during the late quaternary as registered in two galicia bank piston cores 42 n are tentatively explained in terms of shifts in the extent of the outer limit of the local palaeoproductivity belt off the iberian peninsula