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Sea-Level Change (1990) / Chapter Skim
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13 Sea Level and the Thermal Variability of the Ocean
Pages 208-218

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From page 208...
... In the Atlantic, data consisted of 27 yr of repeated deep hydrographic stations near Bermuda, sea level at Bermuda, and two large spatial-scale hydrographic surveys of the subtropical North Atlantic Ocean that were separated in time by 23 yr. In the Pacific, a number of coastal sea-level stations were considered together with a grid of hydrographic stations sampled to 500 m depth in the period 1950 to 1978.
From page 209...
... BERMUDA SEA LEVEL AND THE PANULIRUS DATA The longest regular time-series of deep (>1000 m) hydrographic stations is the Panulirus series (32°10'N, 64°30'W)
From page 210...
... By steric depth, we mean that the specific volume anomaly is integrated downward from the ocean surface to the pressure level indicated by the ordinate. Since the slope of each curve is the specific volume anomaly, it can be seen that the month-to-month changes in specific volume are large in the upper 200 m and small below this level.
From page 211...
... In general, temperature changes are accomplished by salinity changes such that a fairly tight temperature-salinity correlation is maintained. A temperature increase of 1°C in the thermocline at the Panulirus station is accompanied by a salinity change of approximately 0.1 practical salinity units.
From page 212...
... Of central importance here is the relationship between the apparent trends in specific volume and sea level. In Figure 13.7, the 5-yr running mean of Bermuda sea level is shown together with that of the Panulirus steric height of the sea surface relative to 2000 dbar.
From page 213...
... In the lowest frequency bands, the spectra slope more steeply than (frequency) -~, indicating that the ~ ~ 0.10 ~ _ _' ~ ~ I llJ ~ _ llJ I (a LLJ En o - 0.,0 _ _ -_ 7~L 940 1960 1980 YEAR FIGURE 13.7 From top to bottom, S-yr running means of Charleston sea level, Bermuda sea level, Panulirus steric height (O to 2000 dbar)
From page 214...
... THE EASTERN NORTH PACIFIC On a global basis, the great majority of sea-level stations are located along continental coastlines, as opposed to the mid-ocean island station discussed in the previous section. It is anticipated that direct comparisons of steric height with sea level near continental boundaries are subject to additional difficulties not encountered in mid-ocean.
From page 215...
... If there are no strong spatial patterns, what about the overall trend? We averaged the yearly anomalies for all 90 stations, and these yearly averages are shown in Figure 13.12 together with the average sea level.
From page 216...
... But without supporting data, this is pure conjecture. DISCUSSION A principal lesson of the extensive North Atlantic and eastern North Pacific data sets is that steric height variations occur over such a variety of space and time scales that possible trends cannot be identified in the approximately 30-yr time series, no matter how dense the sampling.
From page 217...
... (1972~. Bermuda sea level in relation to tides, weather, and baroclinic fluctuations, Rev.
From page 218...
... term dominates. A thickening of the upper layer (positive Chic raises the sea level by zs = t(P2 - p~/P23Gh~ and thus increases the oneway travel time by Szs; but the relative thickening of the warm (high speed)


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