Showing papers on "World Ocean Atlas published in 2001"

PHC: A Global Ocean Hydrography with a High-Quality Arctic Ocean

Abstract: A new gridded ocean climatology, the Polar Science Center Hydrographic Climatology (PHC), has been created that merges the 1998 version of the World Ocean Atlas with the new regional Arctic Ocean Atlas. The result is a global climatology for temperature and salinity that contains a good description of the Arctic Ocean and its environs. Monthly, seasonal, and annual average products have been generated. How the original datasets were prepared for merging, how the optimal interpolation procedure was performed, and characteristics of the resulting dataset are discussed, followed by a summary and discussion of future plans.

Global and Regional Sea Surface Temperature Trends

Abstract: Individual sea surface temperature (SST) anomalies are calculated using a satellite-based climatology and observations from the World Ocean Atlas 1994(WOA94) and the Comprehensive Ocean‐Atmosphere Data Set (COADS) to characterize global and regional changes in ocean surface temperature since 1942. For each of these datasets, anomaly trends are computed using a new method that groups individual anomalies into climatological temperature classes. These temperature class anomaly trends are compared with trends estimated using a technique representative of previous studies based on 58 latitude‐longitude bins. Global linear trends in the data-rich period between 1960 and 1990 calculated from the WOA94 data are found to be 0.14 86 0.048C decade21 for the temperature class approach and 0.13 86 0.048C decade21 for the 58 bin approach. The corresponding results for the COADS data are 0.10 86 0.038C and 0.09 86 0.038C decade21. These trends are not statistically different at the 95% confidence level. Additionally, they agree closely with both SST and land‐air temperature trends estimated from results reported by the Intergovernmental Panel on Climate Change. The similarity between the COADS trends and the trends calculated from the WOA94 dataset provides confirmation of previous SST trend studies, which are based almost exclusively on volunteer observing ship datasets like COADS. Regional linear trends reveal a nonuniformity in the SST rates between 1945‐70 and 1970‐95. Intensified warming during the later period is observed in the eastern equatorial Pacific, the North Atlantic subtropical convergence, and in the vicinity of the Kuroshio extension. Also, despite close agreement globally, localized differences between COADS and WOA94 trends are observed.

An Isopycnally Averaged North Pacific Climatology

Abstract: Approximately a quarter of a million hydrographic stations extracted from the North Pacific World Ocean Atlas 1994 have been subjected to a statistical quality control to produce a Pacific climatology in the spirit of the Atlantic hydrobase. The CTD casts from the publicly available World Ocean Circulation Experiment (WOCE) and pre-WOCE cruises have also been included, and where available, nutrient data have been retained. Particular attention has been paid to the quality control of the 200 000 stations that lie within the region surrounding Japan as it was determined that much of these data contained suspicious salinity values. A comparison with the gridded World Ocean Atlas 1994 confirms expectations that within deep waters over much of the North Pacific the relatively flat isopycnal surfaces produce only small differences between the two climatologies. Closer to surface, however, the differences between the datasets are far more apparent. The major differences (as large as 1.3°C and 0.2 psu at...

Ocean temperature climate off North‐East New Zealand

Abstract: The ocean temperature field off the north‐east coast of New Zealand is studied to quantify the annual cycle and reveal the intra‐ and inter‐annual variability. The data used are repeat expendable bathythermograph (XBT) sections between Auckland and either Suva or Honolulu which have been collected quarterly since 1986. These sections give temperature measurements between the surface and 800 m and Auckland and 30°S from 1986 to August 1999. The mean and annual cycle are compared with those from the NOAA World Ocean Atlas (WOA98). The results are similar; however WOA98 lacks the horizontal resolution to fully discern the East Auckland Current and North Cape Eddy, while the XBT analysis lacks the temporal resolution to discern higher frequency intra‐annual signals. The temperature variability in the mixed layer is dominated by the annual cycle, which accounts for 80–90% of the variance. The amplitude of the annual cycle diminishes rapidly with depth, from 2.8°C at the surface, to c. 0.1°C at 180 m. ...

Annual and Interannual Changes in the North Atlantic STMW Layer Properties

Abstract: Subtropical mode waters (STWMs) are water masses formed in winter by convective mixing on the equatorward side of western boundary currents in the subtropical gyres. After the return of the seasonal stratification in spring, it is found at the stratification minimum between the seasonal and main pycnoclines. By characterizing STMW primarily at the density gradient minimum, previous studies were limited in their ability to describe STMW properties over large temporal and spatial scales. Rather than using a density-based characterization, the North Atlantic STMW layer was identified here by its much smaller temperature gradient relative to the more stratified seasonal and main thermocline, its temperature, and its large thickness. By using this temperature-based characterization, this study was able to develop a climatology using the large number of XBTs deployed between 1968 and 1988 and contained in the World Ocean Atlas 1994 historical hydrographic database and to use this climatology to examine...

A Characterization of the North Atlantic STMW Layer Climatology Using World Ocean Atlas 1994 Data

Abstract: The North Atlantic Subtropical Mode Water (STMW) layer was identified based on its temperature, large thickness, and small temperature gradient. Comparisons between this method and identifying the STMW layer using a density-based (i.e., potential vorticity) criteria indicate that this method successfully identifies the STMW layer as the remnant of the previous winter’s convective mixing. By using this temperature-based characterization of the STMW layer, this method was able to develop a climatology using the large number of expendable bathythermographs (XBTs) deployed between 1968 and 1988, and contained in the World Ocean Atlas 1994 historical hydrographic database. From this climatology, the STMW layer that is the remnant of the previous winter’s convective activity is typically found between 175 and 450 m, has an average temperature near 18 8C, and has a mean temperature gradient of 0.58C (100 m)21. Comparisons of the STMW temperature, thickness, and temperature gradient characteristics in this climatology agree with other observations of the North Atlantic STMW layer.