Holte James W.

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Last Name
Holte
First Name
James W.
ORCID
0000-0002-3451-7572

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Now showing 1 - 8 of 8
  • Article
    Structure and surface properties of eddies in the southeast Pacific Ocean
    (John Wiley & Sons, 2013-05-07) Holte, James W. ; Straneo, Fiamma ; Moffat, Carlos F. ; Weller, Robert A. ; Farrar, J. Thomas
    A number of studies have posited that coastally generated eddies could cool the southeast Pacific Ocean (SEP) by advecting cool, upwelled waters offshore. We examine this mechanism by characterizing the upper-ocean properties of mesoscale eddies in the SEP with a variety of observations and by estimating the surface-layer eddy heat flux divergence with satellite data. Cyclonic and anticyclonic eddies observed during two cruises featured deep positive salinity anomalies along the 26.5 kg m−3isopycnal, indicating that the eddies had likely trapped and transported coastal waters offshore. The cyclonic eddies observed during the cruises were characterized by shoaling isopycnals in the upper 200 m and cool near-surface temperature anomalies, whereas the upper-ocean structure of anticyclonic eddies was more variable. Using a variety of large-scale observations, including Argo float profiles, drifter records, and satellite sea surface temperature fields, we show that, relative to mean conditions, cyclonic eddies are associated with cooler surface temperatures and that anticyclonic eddies are associated with warmer surface temperatures. Within each data set, the mean eddy surface temperature anomalies are small and of approximately equal magnitude but opposite sign. Eddy statistics drawn from satellite altimetry data reveal that cyclonic and anticyclonic eddies occur with similar frequency and have similar average radii in the SEP. A satellite-based estimate of the surface-layer eddy heat flux divergence, while large in coastal regions, is small when averaged over the SEP, suggesting that eddies do not substantially contribute to cooling the surface layer of the SEP.
  • Article
    An Argo mixed layer climatology and database
    (John Wiley & Sons, 2017-06-12) Holte, James ; Talley, Lynne D. ; Gilson, John ; Roemmich, Dean
    A global climatology and database of mixed layer properties are computed from nearly 1,250,000 Argo profiles. The climatology is calculated with both a hybrid algorithm for detecting the mixed layer depth (MLD) and a standard threshold method. The climatology provides accurate information about the depth, properties, extent, and seasonal patterns of global mixed layers. The individual profile results in the database can be used to construct time series of mixed layer properties in specific regions of interest. The climatology and database are available online at http://mixedlayer.ucsd.edu. The MLDs calculated by the hybrid algorithm are shallower and generally more accurate than those of the threshold method, particularly in regions of deep winter mixed layers; the new climatology differs the most from existing mixed layer climatologies in these regions. Examples are presented from the Labrador and Irminger Seas, the Southern Ocean, and the North Atlantic Ocean near the Gulf Stream. In these regions the threshold method tends to overestimate winter MLDs by approximately 10% compared to the algorithm.
  • Technical Report
    Stratus 11 : Eleventh Setting of the Stratus Ocean Reference Station Cruise on board RV Moana Wave, March 31 - April 16, 2011, Arica - Arica, Chile
    (Woods Hole Oceanographic Institution, 2011-09) Bigorre, Sebastien P. ; Lord, Jeffrey ; Galbraith, Nancy R. ; Whelan, Sean P. ; Otto, William ; Holte, James W. ; Bariteau, Ludovic ; Weller, Robert A.
    The Ocean Reference Station at 20°S, 85°W under the stratus clouds west of northern Chile is being maintained to provide ongoing climate-quality records of surface meteorology, air-sea fluxes of heat, freshwater, and momentum, and of upper ocean temperature, salinity, and velocity variability. The Stratus Ocean Reference Station (ORS Stratus) is supported by the National Oceanic and Atmospheric Administration’s (NOAA) Climate Observation Program. It is recovered and redeployed annually, with past cruises that have come between October and January. A NOAA vessel was not available, so this cruise was conducted on the chartered ship, Moana Wave, belonging to Stabbert Maritime. During the 2011 cruise on the Moana Wave to the ORS Stratus site, the primary activities were the recovery of the subsurface part of the Stratus 10 WHOI surface mooring, deployment of a new (Stratus 11) WHOI surface mooring, in-situ calibration of the buoy meteorological sensors by comparison with instrumentation installed on the ship by staff of the NOAA Earth System Research Laboratory (ESRL), and collection of underway and on station oceanographic data to continue to characterize the upper ocean in the stratus region. The Stratus 10 mooring had parted, and the surface buoy and upper part had been recovered earlier. Underway CTD (UCTD) profiles were collected along the track and during surveys dedicated to investigating eddy variability in the region. Surface drifters and subsurface floats were also launched along the track. The intent was also to visit a buoy for the Pacific tsunami warning system maintained by the Hydrographic and Oceanographic Service of the Chilean Navy (SHOA). This DART (Deep- Ocean Assessment and Reporting of Tsunami) buoy had been deployed in December 2010.
  • Article
    Subantarctic mode water in the southeast Pacific : effect of exchange across the Subantarctic Front
    (John Wiley & Sons, 2013-04-23) Holte, James W. ; Talley, Lynne D. ; Chereskin, Teresa K. ; Sloyan, Bernadette M.
    This study considered cross-frontal exchange as a possible mechanism for the observed along-front freshening and cooling between the 27.0 and 27.3 kg m − 3 isopycnals north of the Subantarctic Front (SAF) in the southeast Pacific Ocean. This isopycnal range, which includes the densest Subantarctic Mode Water (SAMW) formed in this region, is mostly below the mixed layer, and so experiences little direct air-sea forcing. Data from two cruises in the southeast Pacific were examined for evidence of cross-frontal exchange; numerous eddies and intrusions containing Polar Frontal Zone (PFZ) water were observed north of the SAF, as well as a fresh surface layer during the summer cruise that was likely due to Ekman transport. These features penetrated north of the SAF, even though the potential vorticity structure of the SAF should have acted as a barrier to exchange. An optimum multiparameter (OMP) analysis incorporating a range of observed properties was used to estimate the cumulative cross-frontal exchange. The OMP analysis revealed an along-front increase in PFZ water fractional content in the region north of the SAF between the 27.1 and 27.3 kg m − 3 isopycnals; the increase was approximately 0.13 for every 15° of longitude. Between the 27.0 and 27.1 kg m − 3 isopycnals, the increase was approximately 0.15 for every 15° of longitude. A simple bulk calculation revealed that this magnitude of cross-frontal exchange could have caused the downstream evolution of SAMW temperature and salinity properties observed by Argo profiling floats.
  • Technical Report
    Stratus 12 : twelfth setting of the Stratus Ocean Reference Station
    (Woods Hole Oceanographic Institution, 2012-10) Bigorre, Sebastien P. ; Weller, Robert A. ; Lord, Jeffrey ; Galbraith, Nancy R. ; Whelan, Sean P. ; Holte, James W. ; Cifuentes, Ursula ; Sanchez, Eric ; Labbe-Ibanez, Pamela A. ; Raboya, Magda Mindiola ; Oltman, Susan ; Denton, Elsie ; Shambaugh, James
    The Ocean Reference Station at 20°S, 85°W under the stratus clouds west of northern Chile is being maintained to provide ongoing climate-quality records of surface meteorology, air-sea fluxes of heat, freshwater, and momentum, and of upper ocean temperature, salinity, and velocity variability. The Stratus Ocean Reference Station (ORS Stratus) is supported by the National Oceanic and Atmospheric Administration’s (NOAA) Climate Observation Program. It is recovered and redeployed annually. A NOAA vessel was not available, so this cruise was conducted on the Melville, operated by the Scripps Institution of Oceanography. During the 2012 cruise on the Melville to the ORS Stratus site, the primary activities were the deployment of the Stratus 12 WHOI surface mooring, recovery of the previous (Stratus 11) WHOI surface mooring, in-situ calibration of the buoy meteorological sensors by comparison with instrumentation installed on the ship, and collection of underway and on station oceanographic data to continue to characterize the upper ocean in the stratus region. Underway CTD (UCTD) profiles were collected along the track. Surface drifters and subsurface floats were also launched along the track.
  • Article
    The role of air-sea fluxes in Subantarctic Mode Water formation
    (American Geophysical Union, 2012-03-29) Holte, James W. ; Talley, Lynne D. ; Chereskin, Teresa K. ; Sloyan, Bernadette M.
    Two hydrographic surveys and a one-dimensional mixed layer model are used to assess the role of air-sea fluxes in forming deep Subantarctic Mode Water (SAMW) mixed layers in the southeast Pacific Ocean. Forty-two SAMW mixed layers deeper than 400 m were observed north of the Subantarctic Front during the 2005 winter cruise, with the deepest mixed layers reaching 550 m. The densest, coldest, and freshest mixed layers were found in the cruise's eastern sections near 77°W. The deep SAMW mixed layers were observed concurrently with surface ocean heat loss of approximately −200 W m−2. The heat, momentum, and precipitation flux fields of five flux products are used to force a one-dimensional KPP mixed layer model initialized with profiles from the 2006 summer cruise. The simulated winter mixed layers generated by all of the forcing products resemble Argo observations of SAMW; this agreement also validates the flux products. Mixing driven by buoyancy loss and wind forcing is strong enough to deepen the SAMW layers. Wind-driven mixing is central to SAMW formation, as model runs forced with buoyancy forcing alone produce shallow mixed layers. Air-sea fluxes indirectly influence winter SAMW properties by controlling how deeply the profiles mix. The stratification and heat content of the initial profiles determine the properties of the SAMW and the likelihood of deep mixing. Summer profiles from just upstream of Drake Passage have less heat stored between 100 and 600 m than upstream profiles, and so, with sufficiently strong winter forcing, form a cold, dense variety of SAMW.
  • Article
    Seasonal overturning of the Labrador Sea as observed by Argo floats
    (American Meteorological Society, 2017-10-17) Holte, James ; Straneo, Fiamma
    Argo floats are used to investigate Labrador Sea overturning and its variability on seasonal time scales. This is the first application of Argo floats to estimate overturning in a deep-water formation region in the North Atlantic. Unlike hydrographic measurements, which are typically confined to the summer season, floats offer the advantage of collecting data in all seasons. Seasonal composite potential density and absolute geostrophic velocity sections across the mouth of the Labrador Sea assembled from float profiles and trajectories at 1000 m are used to calculate the horizontal and overturning circulations. The overturning exhibits a pronounced seasonal cycle; in depth space the overturning doubles throughout the course of the year, and in density space it triples. The largest overturning [1.2 Sv (1 Sv ≡ 106 m3 s−1) in depth space and 3.9 Sv in density space] occurs in spring and corresponds to the outflow of recently formed Labrador Sea Water. The overturning decreases through summer and reaches a minimum in winter (0.6 Sv in depth space and 1.2 Sv in density space). The robustness of the Argo seasonal overturning is supported by a comparison to an overturning estimate based on hydrographic data from the AR7W line.
  • Article
    Heat and salinity budgets at the Stratus mooring in the southeast Pacific
    (John Wiley & Sons, 2014-11-28) Holte, James W. ; Straneo, Fiamma ; Farrar, J. Thomas ; Weller, Robert A.
    The surface layer of the southeast Pacific Ocean (SEP) requires an input of cold, fresh water to balance heat gain, and evaporation from air-sea fluxes. Models typically fail to reproduce the cool sea surface temperatures (SST) of the SEP, limiting our ability to understand the variability of this climatically important region. We estimate the annual heat budget of the SEP for the period 2004–2009, using data from the upper 250 m of the Stratus mooring, located at 85°W 20°S, and from Argo floats. The surface buoy measures meteorological conditions and air-sea fluxes; the mooring line is heavily instrumented, measuring temperature, salinity, and velocity at more than 15 depth levels. We use a new method for estimating the advective component of the heat budget that combines Argo profiles and mooring velocity data, allowing us to calculate monthly profiles of heat advection. Averaged over the 6 year study period, we estimate a cooling advective heat flux of −41 ± 29 W m−2, accomplished by a combination of the mean gyre circulation, Ekman transport, and eddies. This compensates for warming fluxes of 32 ± 4 W m−2 due to air-sea fluxes and 7 ± 9 W m−2 due to vertical mixing and Ekman pumping. A salinity budget exhibits a similar balance, with advection of freshwater (−60 psu m) replenishing the freshwater lost through evaporation (47 psu m) and Ekman pumping (14 psu m).