OS13A-0995
Transport processes of Plutonium isotopes in the NW Pacific margin
Over the past years, we have made a systematic investigation on the distribution of Pu isotopes in the NW Pacific Ocean and its adjacent seas. More than 30 sediment cores were collected in the western North Pacific and its adjacent seas, namely, the East China Sea, Okinawa Trough, the Japan Sea and the Okhotsk Sea. Based on the obtained 240Pu/239Pu ratio signature, we identified the wide presence of Bikini close-in fallout Pu in the studied regions, which contributed to the excess Pu inventories. We propose that the oceanic process is responsible for the wide presence of Bikini close-in fallout Pu. Using a two fallout end-member model, we resolved the relative contribution of Pu between global fallout and close-in fallout in sediments. It was concluded that the contribution of Bikini close-in fallout Pu ranged from 10 % to 60 % in the studied regions. To verify our hypothesis on the oceanic process for the transport of Pu in the Pacific Ocean, we further investigated the Pu isotopic signature in seawater and settling particles in the western Northwest Pacific. It was found that Pu isotopes from the two sources of global fallout and close-in fallout have been homogenized in the water masses in the western Northwest Pacific margin during the past four decades. Settling particles have been regarded as the primary means by which surface-introduced Pu is transported to the sediments. We carried out a sediment-trap experiment in the western Northwest Pacific to investigate Pu isotopes in settling particles. To the best of our knowledge, this is the first time that both Pu activity and Pu isotope ratio data have been obtained for settling particles in the Pacific Ocean. The 240Pu/239Pu atom ratios are quite constant; the change of total mass flux in the different seasons did not result in a variation of Pu atom ratios in settling particles. The high 240Pu/239Pu atom ratios (0.23-0.27) in settling particles confirmed that Pu from the PPG source in the central Pacific is transported toward the western Northwest Pacific. Three transport processes were identified to be responsible for the distribution and fate of Pu isotopes in the NW Pacific margin: (1) advective lateral transport of dissolved Pu from open ocean to ocean margin; (2) vertical transport of Pu isotopes via particle scavenging; and (3) the bottom layer lateral transport and redistribution of Pu isotopes.
OS13A-0996
Decadal Variations of the Subtropical Front in a North Pacific Eddy Resolving OGCM
Variations of both the subtropical front (STF) and the subarctic front (SAF) are related to the two dominant modes of the North Pacific SST on decadal timescale. Although there have been many studies on the variation of the SAF, the variation of the STF has not been well understood because of temporal and spatial scarcity of observed data. In this study, decadal variations of the STF are examined with a North Pacific ocean general circulation model (OGCM). The OGCM we employed is based on the Meteorological Research Institute Community Ocean Model (MRI.COM). The model domain is the North Pacific north of 15{°}S. The model is driven by the daily surface fluxes of momentum, heat, and freshwater derived from the NCEP/NCAR atmospheric reanalysis data for the period 1949- 2005. Three types of simulations with different horizontal resolutions are compared. On the long-term mean fields, an eddy resolving model (1/12°) was able to simulate the distributions of the STF and the associated subtropical counter current (STCC) between 20{°}N and 30{°}N, better than a non-eddy resolving model (1°) and an eddy-permitting model (1/4° x 1/6°), reflecting the more realistic representation of the simulated Kuroshio recirculation gyre in the eddy resolving model. The simulated STF showed a significant decadal variation; the strength of the STF was relatively strong in 1975/79, while it was relatively weak in 1990/94. The decadal-scale STF change was largely explained by the corresponding variability of the mode waters, which were formed in the western North Pacific and advected to the north of the STF by the subtropical gyre. The relationship between the decadal variation of the STF and surface fluxes is also discussed.
OS13A-0997
Tracer Tubes: A New Inverse Technique for Estimating Water-Mass Subduction and Mixing Coefficients
A new "Tracer Tube" or "TT" inverse technique for estimating the vertical and lateral mixing coefficients and the lateral transport down temperature and salinity gradients on isopycnal layers will be presented. The technique combines equations for the balance between diffusion processes and the non-adiabatic lateral flow along density surfaces. The technique is over-determined, does not require a priori information and avoids much of the signal to noise error associated with differentiating hydrographic data in conventional inverse techniques. The TT inverse technique is being applied to output of a layered model (HIM). Early results indicate that it can accurately resolve both lateral and vertical diffusivities as well as the subduction rates of different water masses down sloping isopycnals in an area of the southern ocean.
OS13A-0998
Tracing Water Masses Along the subtropical South American Coast with the Stable Isotopic Composition of Benthic Foraminifera
We explore the applicability of stable isotopic ratios of various indicator species of benthic foraminifera ( Uvigerina peregrina, Pseudononion atlanticum, Hoeglundina elegans, Angulogerina angulosa, Buccella peruviana, Cibicides fletcheri, Cassidulina subglobosa, Bulimina marginata and Hanzawaia boueana) to identify bottom water masses. Samples were collected along the continental shelf of the Argentinean-Uruguayan and Brazilian Atlantic Coast during the winter 2003 and summer 2004. Results show that the stable isotopic composition of living and dead foraminifera is associated with environmental variables (latitude, depth, temperature, salinity and nutrients). Specifically, the δ18O data from Uvigerina peregrina, Hoeglundina elegans and Pseudononion atlanticum follow meridional temperature gradients with the presence of relatively warm Subtropical Shelf Water indicated by lower δ 18O values at the northernmore sites (27° S) and colder Subantarctic Shelf Water with higher δ18O values toward the southern sites (to 37° S). Angulogerina angulosa and Pseudononion atlanticum δ18O values correlated better with salinity than temperature. Results also indicate that δ13C values from Uvigerina peregrina, Hoeglundina elegans, Bulimina marginata and Cassidulina subglobosa tend to be low at sites located within the freshwater plume of the La Plata River. These results suggest that it is possible to identify three regional water masses based on the stable isotopic compositon of these various indicator species.
OS13A-0999
Volumes of the World's Oceans From ETOPO2v2
We have calculated the volumes of the world's oceans from the 2 arc-minute ETOPO2v2 global relief model assembled by the National Geophysical Data Center. Total: 1,332 x 10\textsuperscript{6} km\textsuperscript{3}. Pacific Ocean: 659 x 10\textsuperscript{6} km\textsuperscript{3}. Atlantic Ocean: 306 x 10\textsuperscript{6} km\textsuperscript{3}. Arctic Ocean: 18.7 x 10\textsuperscript{6} km\textsuperscript{3}. Indian Ocean: 263 x 10\textsuperscript{6} km\textsuperscript{3}. Southern Ocean: 71.0 x 10\textsuperscript{6} km\textsuperscript{3}. Mediterranean region: 4.41 x 10\textsuperscript{6} km\textsuperscript{3}. South China and Eastern Archipelagic seas: 9.78 x 10\textsuperscript{6} km\textsuperscript{3}. Baltic Sea: 21.2 x 10\textsuperscript{3} km\textsuperscript{3}. Ocean limits were derived from IHO Special Publication No. 23 and represented in ArcGIS polygon format. Ocean volumes were determined by clipping the ETOPO2v2 digital elevation model to the appropriate polygon (to prevent inclusion of dry elevations below sea level), calculating the area of each grid cell (using the WGS84 spheroid), and summing the volumes (area x depth) of grid cells below sea level. This methodology can be extended to any ocean basin or other region where a digital elevation model has been generated. We anticipate that our refined ocean volume calculations will prove useful to physical oceanographic studies, climate modeling, and other research that uses ocean volumes as a prerequisite input.
OS13A-1001
Rossby waves detected in HYCOM sea surface salinity in the Indian Ocean
We demonstrate for the first time the detectability of Rossby waves in sea surface salinity in the Indian Ocean by using simulations of the 1/12° global Hybrid Coordinate Ocean Model (HYCOM). HYCOM results compared favorably to SSS data provided by Argo floats in selected grid boxes in the Indian Ocean. Hovmöller diagrams of HYCOM SSS anomalies and gradient show the distinct westward propagating signature of Rossby waves, with a steeper slope in longitude/time plots further from the equator. The propagation speeds, calculated from a 2D Radon Transform are comparable with new theoretical speeds for Rossby waves. Annual westward propagating signals in the SSS simulations at most of the latitudes in the Indian Ocean coincide with previous studies. We hope that future studies of Rossby waves in SSS using model results and eventually satellite measurements of salinity data from Aquarius and SMOS will allow a better understanding of Rossby wave dynamics.
OS13A-1002
Regional variability of sea level change using a global ocean model.
We analyse different runs of a global eddy-permitting (1/4 degree) ocean model driven by atmospheric forcing to evaluate regional variability of sea level change over 1993-2001, 1998-2006 and over the long period 1958-2004. No data assimilation is performed in the model, contrarily to previous similar studies (Carton et al., 2005; Wunsch et al., 2007; Koehl and Stammer, 2007). We compare the model-based regional sea level trend patterns with the one deduced from satellite altimetry data. We examine respective contributions of steric and bottom pressure changes to total regional sea level changes. For the steric component, we analyze separately the contributions of temperature and salinity changes as well as upper and lower ocean contributions.
OS13A-1003
Upper mixed layer temperature and salinity variability in the tropical boundary of the California Current
In eastern boundary current, eddies, meanders, fronts, and coastal upwelling are the main processes in the generation of mesoscale variability. Seasonal variability of the integrated temperature in the quasi-isothermal layer depth and the integrated salinity in the quasi-isohaline layer depth of the southern part of the California Current are examined using hydrographic data from thirty six surveys carried out from 1997 to 2006 over a grid based on the Mexican Research of the California Current (IMECOCAL) stations plan. The sampling interval was approximately 3-month. The spatial patterns of the first leading Empirical Orthogonal Function (EOF) for both the integrated temperature and the integrated salinity showed a single-signed distribution with a northward decreasing variability. We hypothesized that this pattern is explained by the mesoscale variability difference between the southern and the northern Baja California zones. To test our conjecture, we used altimeter measurements to compute eddy kinetic energy in both zones. The spatial pattern of the second leading EOF for the integrated temperature showed a double-signed distribution, separating the costal zone from the transition one. This mode was correlated with costal upwelling index. The spatial pattern of the second leading EOF for the integrated salinity showed a double signed-distribution, separating the northern region from the southern region off Punta Eugenia. This mode was associated with a local front. For the principal component time series of the first leading EOF, we found that seasonal variations of the integrated temperature were connected to wind stress dynamics and air-sea exchange of heat, while the seasonal changes of the integrated salinity were mainly related to wind stress dynamics. http://imecocal.cicese.mx
OS13A-1004
Work done by the Wind on the Geostrophic Ocean Circulation: The Effect of Small Scales in the QuikSCAT Wind Stress Data.
It has recently been noted that the effect of ocean currents on wind stress is visible in data from the QuickSCAT scatterometer. Duhaut and Straub suggested that this effect could have a significant impact on the work done on geostrophic currents by winds, reducing it by of order 20% in comparison to estimates which do not account for the effect of currents on wind stress. We calculate the work done, using a combination of wind stress (including the current effect) from scatterometer data, and currents from altimetry, drifter, and satellite gravity data. We find a global total of 0.76 TW, smaller than previous estimates, together with an estimate that the effect of currents should produce a reduction of 0.19 TW. This means that, if the data we are using are sufficiently well-sampled to resolve the correlations responsible for the current effect, calculations which do not account for the current effect would produce an estimate of 0.95 TW, a number which lies within the range of previous estimates. We test whether the sampling is sufficient by calculating the power based on a spatially smoothed version of the wind stress, which removes the effect of small-scale currents. This power is larger to approximately the expected degree in midlatitude regions, but not in the tropics, where something more complicated appears to be happening. The contribution of time-dependent terms to the average power produces a similar effect in regions dominated by mesoscale eddies.
OS13A-1005
Measured and Modeled Currents at a Deep Ocean Volcano: Brothers
Ocean currents to depths of 1600 m at Brothers volcano (34° 52.25' S, 179 ° 04' E) north of New Zealand have been measured and modeled. Three moorings separated laterally by only 10 km and sampling from September 2004 to May 2005 show high energy flows near summit depth (1300 m) with average speeds > 6 cm s-1 and maximum speeds > 17 cm s-1. A primitive equation model shows observed flows to be part of a anticyclonic flow toroidaround Brothers' summit with current maxima of approximately 5 cm s-1. Nearer the sea surface (200-500 m) M2 tidal currents vary in amplitude by a factor of three, suggesting that internal tides bathe the site. The variation of sub-tidal currents at the shallowest three current meters is mimicked by time series of geostrophic currents based on Aviso sea level anomalies (SLA). Sea level anomaly distributions over the site often show an E-W oriented SLA ridge to the south of Brothers, which causes westward surface flow; less frequently SLA gradients are in the E-W direction, resulting in intermittent meridional flows.
OS13A-1006
Seasonal and Fortnightly Variability of Baroclinic Tides in the Luzon Strait and Northern South China Sea: A Numerical Study
The seasonal and fortnightly variations of baroclinic tides in the Luzon Strait and northern South China Sea are investigated using a three-dimensional tide model driven by four tidal constituents, O1, K1, M2 and S2, separately. Historical CTD data collected at the South East Asia Time-Serious (SEATS) station are used to compute vertical profiles of temperature and salinity in summer and winter, which are used as initial conditions for the present model study. Diurnal and semidiurnal baroclinic tides have a comparable energy flux away from the Luzon Strait. The barotropic to baroclinic conversion rate is about 30% each. Both east and west ridges are active in generating baroclinic tides. There appears no significant seasonal variation of the baroclinic tidal energy flux. Fortnightly variations are strong. Baroclinic tidal energy flux stems from the east ridge in the southern Luzon Strait and that from the west ridge in the northern Luzon Strait combine and form a strong tidal beam immediately west of the west ridge. This semidiurnal baroclinic energy flux is likely the energy source of nonlinear internal waves found in the South China Sea.
OS13A-1007
Influence of the Daily Variability of Surface Heat Loss on Deep Convection
Deep convection occurs in regions of the ocean where strong buoyancy loss from a preconditioned ocean to the atmosphere leads to a very deep mixed layer. In a one-dimensional approach, the deepening of the mixed layer depends on the integrated value of the buoyancy loss, but this surface loss is highly variable in time. In the Gulf of Lion, for example, the mean winter surface heat loss is about 200 W/m2, but can reach values higher than 500 W/m2 for very short times (typically 2 days). The effect of this short-term variability is investigated using an idealised model. The MIT model is integrated over a square box of size 64km x 64 km x 2km initialised with homogeneous salinity and a linear vertical temperature gradient. A time-periodic cooling is then applied over a disc of radius 20km at the centre of the surface of the box. All the time-periodic forcing have the same integrated value, but different shapes with periods of either 4, 10 or 20 days. The depth of the mixed layer does not seem to depend on this time-variability, but only on the integrated value of the heat flux. Lateral buoyancy fluxes out of the patch are investigated, as well as their vertical structure, which shows that most of the buoyancy gains take place close to the surface.
OS13A-1008
Change of Thermal Core for Kuroshio in the East China Sea
The thermal core of the Kuroshio in the East China Sea (ECS) sorted out by 5 % the high temperature region from surface to 500m depth using the data from World Ocean Atlas 2005. It is found, that the thermal core of the Kuroshio in ECS is close to west side on the surface, the thermal core moves toward east with depth increasing, it close to east side below 100m. At the northeast sea area of Taiwan island, the thermal core of the Kuroshio in ECS is close to continental shelf of ECS, there is a sharp bend for the thermal core, which turns from north to east. The point of elbow moves with season, it is close to the northmost side in summer and to the southmost in spring. There is another sharp bend for the thermal core at the southwest sea area of Kyushu, with turns from northeast to east. The point of elbow is close to the northeast in summer.
OS13A-1009
Frequency and zonal wavenumber spectra of altimetric sea level in the North Pacific as revealed by 9 years of TOPEX data
These two-dimensional spectra show the prevalence of free baroclinic Rossby waves from the equatorial region to the mid-latitudes. An innovation based on segregating the Fourier components into standing and propagating modes has helped reveal the Rossby waves more clearly where they have been obscured previously by the seal- level signatures of the seasonal heating and cooling cycle. It is found that the linear theory of Rossby waves applies well for most of the ocean (i.e., ignoring zonal and meridional density variations associated with the mean flow) with the possible exception in regions closer to the western boundary currents. That is, the Rossby wave speed is more or less uniform zonally across the North Pacific except closer to the western end in mid- latitudes. From the zonal and meridional distribution of the power of these Rossby waves, the source of these waves can be deciphered.
OS13A-1010
Detection of internal tidal waves on the Kerguelen plateau from altimetry
We use a 15 year time serie of Topex/Poseidon data to detect internal tides on the Kerguelen plateau. In order to better represent and caracterise the properties of the internal tides, we use a high resolution model developed around the Kerguelen plateau and a dedicated data processing system also developed at LEGOS : the X-Track tool. Among other improvements, this software uses the high resolution regional MOG2D model for the high frequency de-aliasing, a refined data editing strategy in coastal ocean areas, a higher sampling rate processing (up to 4Hz), a local mean sea surface consistent with the altimetric data set.
OS13A-1011
A 10-15year Modulation Cycle of ENSO Intensity and its ENSO Asymmetry-Basic State Interaction Mechanism
A 10-15year decadal modulation cycle of ENSO intensity is identified from historical data and paleoclimate proxy based on the "envelope function" of Nino3.4 SST anomalies. Further composite analyses reveal significant spatial asymmetries between El Nino and La Nina within this modulation cycle. During the strong-ENSO-intensity periods of the cycle, SST anomalies center in the eastern Pacific for El Nino but in the central Pacific for La Nina; while during the weak-ENSO-intensity periods, the spatial asymmetry pattern is reversed. It is demonstrated that the El Nino-La Nina asymmetries allow ENSO to interact with the Pacific basic state to give rise to the 10-15year ENSO intensity modulation cycle. The ENSO asymmetry-basic state interaction mechanism is manifested by the east-west shifting of the Pacific Walker circulation. The migration of the mean location of Walker circulation changes the mean patterns of surface wind and thermocline slopes along the equatorial Pacific, and then sets the stages for the ENSO asymmetry to switch, leading to the slow modulation cycle. This study finds that the decadal modulation of ENSO intensity is closely linked with the slowly varying basic state in the tropical Pacific through ENSO asymmetry and can be self-sustained without the need of external forcing. Model experiments performed with NCAR CCSM3 is also used to further demonstrate this decadal modulation mechanism.
OS13A-1012
Surface Wind Speed from Deep-Ocean Acoustic Levels
The ALOHA Cabled Observatory (ACO) is located about 100 km north of Oahu, Hawaii. Comparison of surface wind speeds measured at the WHOTS buoy at Station ALOHA with acoustic levels measured at the ACO on the ocean floor 4780 m below reveals strong correlation between surface wind speed and acoustic levels in several frequency bands. Characteristics of the acoustic spectra suggest that at least three different mechanisms are involved in the transfer of wind energy to the ocean floor. Characteristics of data in at least one of these bands, between 0.5 and 5 Hz, are not predicted by current theories. The correlation of surface winds with acoustic levels has been reported previously from other regions, but in this paper we analyze data acoustic from 0.03 Hz to 12 kHz and correlate it with WHOTS wind speeds between 2 and 10.5 m/s, limited by the range of observed wind speeds. Acoustic levels lag the wind speeds by 0 to 10 hours and saturation of the acoustic levels in some frequency bands implies a related correlation with the wind wave spectrum. Transient signals unrelated to wind speed add noise to the correlation, but since different transients are observed in different frequency bands, they can be removed from the signal. The strong correlations imply that recorded acoustic levels can be used as a proxy for surface wind speeds in historical data. The ACO was installed at Station ALOHA in mid February 2007, utilizing the retired HAW-4 commercial electro- optical telecommunications cable. The initial installation involved cutting the cable, moving it to Station ALOHA, splicing on a termination, and lowering it to the ocean floor with a set of preliminary sensors consisting of a broadband hydrophone and pressure sensor. The full observatory infrastructure will be installed in November 2007, using the JASON ROV. At that time, the infrastructure will be available to service up to eight sensor systems with about 100 W of continuous electrical power and a continuous 10 Base-T Ethernet link for each sensor system, expandable to 4-times that capacity as required. http://www.soest.hawaii.edu/GG/DeepoceanOBS/
OS13A-1013
Variability Scales of Sea Surface Salinity
The variability of sea surface temperature (SST) and salinity (SSS) were investigated from the monthly World Ocean Atlas (WOA) Climatology. First, the zonal means and standard deviations were constructed for each 10° latitude bins from the climatology. Both the SST and SSS zonal means are nearly symmetric about the ITCZ between the hemispheres. There are differences in the zonal standard deviation however, with SST variability being nearly symmetric about the ITCZ and the SSS variability having a much smaller variability south of 20° S. It was presumed that this lack of variability in the SSS is due to the lack of data that went in to constructing the climatology in the southern hemisphere. Results from a global ocean general circulation model were used to do similar analysis to investigate the variability in the southern hemisphere. As part of the NASA Aquarius mission sea surface salinity forward model, the fully global Hybrid Coordinate Ocean Model (HYCOM) at 2° and 0.72° horizontal resolutions is set up to provide surface salinity and temperature inputs to simulate the brightness temperatures at the satellite. After an initial 30 year spin-up to near-dynamic equilibrium using COADS forcing, a 9 year simulation is conducted using the NCEP reanalysis forcing and monthly river discharge to produce three 3 year realizations of surface salinity that will cover low, medium and high solar activity periods. Maximum variability in the model SSS occurs primarily along the ITCZ region and in the regions of significant river flow. While these results are generally consistent with climatological estimates, the variability magnitude is slightly lower on the order of 0.2 psu except in the regions of strong river inputs and in Bay of Bengal. In general, the variability in the model is lower than in the climatology. However, the zonal means estimated from the model also show a smaller variability in the southern hemisphere for SSS. Additionally, multiple runs from the 2° model forced with different datasets show a very similar nature of SSS variability magnitude south of 20° S of less than 0.2 psu (mostly on the order of 0.1 psu). Therefore, our conclusion is that the smaller SSS variability in the southern hemisphere is not the artifact of data voids, although the lack of data may create some local variability due to mismatch in the time of acquisition. This issue is further investigated with the use of the Argo near-surface salinity data.
OS13A-1014
Central Pacific and Eastern Pacific Types of ENSO
n this study, surface ocean observational and subsurface ocean assimilation data are examined to demonstrate that there exits two distinct types of El Nino Southern Oscillation (ENSO): a traditional eastern Pacific (EP) -type of ENSO and a less-studied central Pacific (CP) -type of ENSO. The EP-type of ENSO is characterized by a sea surface temperature (SST) anomaly centers in the eastern tropical Pacific, westward propagation, basin-wide thermocline variation, shallower thermocline, more sensible to the subsurface processes and remote surface wind response. In contrast, the CP-type of ENSO is characterized by local air-sea interaction with its SST, surface wind, and SST anomalies confined mostly in the central Pacific. The underlying generation mechanisms, spatial structures and evolutions of these two types of ENSO will be discussed. Advanced indices based on SST and ocean heat content (OHC) are developed to better separate these two types of ENSO. It is found that since 1958 until 2001, all the strong El Nino events are EP-type of ENSO while all the strong La Ninas are CP-type of ENSO. Also, a CP type of La Nina usually comes after a EP-type of El Nino. The indices defined based on OHC can not only demonstrate the independence and relationships between these two types of ENSO but also capture the ENSO events better than single Nino SST index. This study suggests that more insights of ENSO dynamics may be obtained using ENSO indices defined with subsurface ocean information.
OS13A-1015
Regional Comparison of Surface Turbulent Flux Products
The surface turbulent fluxes (sensible heat, latent heat, and stress) are an important mechanism by which the atmosphere interacts with the ocean. For example, the air-sea exchange of heat plays an important role in driving the large scale atmospheric circulation as well as regulating the sea surface temperature. Wind stress at the surface is an important driving force for ocean currents. Thus, accurate global fields of the turbulent fluxes are crucial to the understanding of ocean/atmosphere variability. This study compares the surface turbulent fluxes from nine products and investigates the differences on both basin-wide and regional scales over the Atlantic, Pacific, and Indian Oceans. The forcing variables are also examined to identify causes for differences in the derived flux products. The products based on weather models include the 2nd NCEP reanalysis, ECMWF 40-yr reanalysis (ERA-40), and Japanese 25-yr reanalysis (JRA-25). Data sets based on in situ observations include NOC (formerly SOC) and FSU3. Purely satellite derived products include those from Goddard (GSSTF2), IFREMER, and the 2nd version of HOAPS. A hybrid NWP model and satellite product from WHOI is also included in this comparison. Zonal averages of the stresses and heat fluxes reveal very large differences amongst the various products. For the Atlantic Ocean, the largest differences in the zonally averaged latent and sensible heat fluxes exceed 60 Wm-2 and 15 Wm-2 respectively. Comparable differences are also found over the Pacific and Indian Oceans. These differences are large from the point of view of climate modeling. Regional analysis of the distribution of the fluxes shows large variations between products at all quantiles. For example, NCEPR2 has a large inter-quantile range and unrealistic values at the 1st and 99th percentile in the tropics. In some regions, median latent heat flux values differ by 40 Wm-2 between products.
OS13A-1016
ENSO and NAO as Markov chains: runs of states
We use a simple three-state Markov chain model in order to study the number of runs or spells of hot, cold and neutral months for El Niño/Southern Oscillation (ENSO) and for the North Atlantic Oscillation (NAO), as reported in the page http://www.cdc.noaa.gov/ClimateIndices/List/. We discuss the fit of the Markovian model to both phenomena and the differences between the run statistics (proportions of the number of runs over the number of transitions and over the total number of runs) for ENSO and NAO.
OS13A-1017
Long-Range Propagation of Semidiurnal Internal Tides in the North Pacific Ocean
Internal tides provide a major energy source to drive the oceanic meridional overturning circulation, whose variation has profound implications for global climate change. In the North Pacific Ocean, the long-range propagation of semidiurnal internal tides is studied using field moorings and TOPEX/Poseidon (T/P) altimeter data. Moorings, at the cost of greatly reduced spatial coverage, can detect both the coherent and incoherent internal tides. T/P altimeter data have continuous global coverage, but can only detect the coherent internal tides. In this study, we develop a phase adjustment method (different from the conventional harmonic analysis) to extract internal tides from the altimeter data. This new method and the use of both the original and tandem T/P along-track data allow us to 1) separate the southward and northward internal tides, and 2) identify narrow internal-tide beams as a result of the improved spatial resolution. These results reveal a new view of the internal-tide field in the North Pacific Ocean. Internal-tide beams can propagate a longer distance than previously thought. Two northward beams radiating from the Hawaiian Ridge propagate across the North Pacific Ocean (more than 3000 km) and reach the Alaskan shelf. The originally overlapped southward Aleutian beams and northward Hawaiian beams are separately resolved. The discrepancies between previous altimetric and moored fluxes are also reduced, indicating that the low spatial resolution and temporal incoherence were the causes.
OS13A-1018
Development of Bio-Optical Algorithms for Geostationary Ocean Color Imager
GOCI, the first Geostationary Ocean Color Imager, shall be operated in a staring-frame capture mode onboard its
Communication Ocean and Meteorological Satellite (COMS) and tentatively scheduled for launch in 2008. The
mission concept includes eight visible-to-near-infrared bands, 0.5 km pixel resolution, and a coverage region of
2,500 вовп 2,500 km centered at Korea. The GOCI is expected to provide SeaWiFS quality observations for a
single study area with imaging interval of 1 hour from 10 am to 5 pm. In the GOCI swath area, the optical
properties of the East Sea (typical of Case-I water), the Yellow Sea and East China Sea (typical of Case-II water)
are investigated. For developing the GOCI bio-optical algorithms in optically more complex waters, it is necessary
to study and understand the optical properties around the Korean Sea. Radiometric measurements were made
using WETLabs AC-S, TriOS RAMSES ACC/ARC, and ASD FieldSpec Pro Dual VNIR Spectroradiometer.
Seawater samples were collected concurrently with the radiometric measurements at about 300 points around
the Korean Sea during 1998 to 2007. The absorption coefficients were determined using Perkin-Elmer Lambda
19 dual-beam spectrophotometer. We analyzed the absorption coefficient of sea water constituents such as
phytoplankton, Suspended Sediment (SS) and Dissolved Organic Matter (DOM). Two kinds of chlorophyll
algorithms are developed by using statistical regression and fluorescence-based technique considering the bio-
optical properties in Case-II waters. Fluorescence measurements were related to in situ Chl-a concentrations to
obtain the Flu(681), Flu(688) and Flu(area) algorithms, which were compared with those from standard spectral
ratios of the remote sensing reflectance. The single band algorithm for
OS13A-1019
Global Hydrographic Overview of Ocean Near Surface Variability
Estimates of hydrographic variability as measured by ARGO drifters in the near surface layer of the world ocean are discussed here. A gridded global field of these hydrographic measurements is used which is disposed by the CORIOLIS Analysis System (CAS). The estimates explicitly include the description of the seasonal cycle of temperature as well as of the salinity field, depict large-scale variability patterns in the different oceanic basins and its main purpose is to provide an insight into what can be measured and resolved in the upper layer while using the CAS gridded field. Amplitudes of total variance are generally higher in the northern hemisphere compared to its southern counterpart. The distribution of standard deviations of temperature including the seasonal cycle as well as from temperature anomalies highly differs from corresponding salinity variability which can be predominantly lead back to ocean atmosphere dynamics. Large-scale and well known oceanic features such as ocean's response to NAO and PDO fluctuations and ENSO dynamics can be resolved in CAS temperatures. A substantial advance using the CAS gridded field is that its signatures in global salinity can also be discussed.
OS13A-1020
Non-normal dynamics in an idealized ocean GCM
An idealized configuration of the MIT-General Circulation Model (MITgcm) is used to investigate the non-normal dynamics of the Atlantic ocean circulation. In a double-hemisphere ocean basin, we find that appropriate initial conditions of sea surface height, temperature, salinity, zonal and meridional velocities can lead to an amplification by two orders of magnitude of the total integrated perturbation-energy (potential, internal and kinetic) after 5 years. The model is in a stable regime, and therefore this perturbation eventually decays. The transient growth found is evidence for a significant non-normality of the stable linearized dynamical operator. The optimal initial conditions leading to the transient amplification of the total perturbation-energy of the ocean are obtained by solving a generalized eigenvalue problem. The evaluation of the optimals is achieved by using the tangent linear and adjoint models of MITgcm as well the ARPACK software aimed to solve large scale eigenvalue problems. Our results suggest that transient amplification of ocean thermohaline and wind driven circulation perturbations due to stochastic forcing may be an efficient way to create large scale ocean variability. The impact of such perturbations on the model heat and volume transport via transient growth is analyzed.