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Fig. 3.5.2 Conceptual schematic of the WOCE Data Resource. products) better satisfies a range of generic user needs during the WOCE Analysis, Interpretation, Modelling and Synthesis (AIMS) phase. The aim of the Data Resource is to provide researchers with an interface through which a wide range of WOCE data and data products may be accessed without concern for the complex internal structure and distributed nature of the WOCE data infrastructure. The WOCE Data Resource allows integrated data...

Info

As illustrated, the long-term fluctuations (5-year mean) of Kuroshio transport and Kuroshio throughflow at 137 E show both similarities and differences low values in the early 1970s are common to both series, but the slight upward trend thereafter in 'Kuroshio' transport appears to be maintained through the 1980s into the 1990s, while that of 'Kuroshio throughflow' begins to decline. The Sverdrup transport, inferred from the wind stress curl field, agrees better with the transport of...

Evidence of water mass changes in the Pacific and Indian Oceans

Here we focus on large-scale changes observed in three distinct intermediate water masses of the Pacific and Indian Oceans Sub-Antarctic Mode Water (SAMW), Antarctic Intermediate Water (AAIW) and North Pacific Intermediate Water (NPIW), all of which are key components of the thermohaline circulation in these regions. Typically, we compare observations from the 1960s and 1970s with WOCE hydrographic data from the late 1980s and early 1990s and are therefore describing the observed differences...

WTimothy Liu and Kristina B Katsaros

The ocean circulation is forced at the surface through exchanges with the atmosphere of momentum, heat and water. The wind exerts a stress on the surface, which alone can produce many features of ocean currents in observations and in numerical model analyses. The buoyancy due to cooling and heating at the surface, and salt concentration or dilution due to evaporation or precipitation, likewise can also generate much of the observed circulation pattern. The real ocean combines these varying...

The analysis of decadal change in intermediate water masses of the World Ocean

The oceans play a central role in defining the earth's climate, transporting heat and fresh water around the globe as part of the thermohaline circulation (e.g. Broecker, 1997). Models of climate change predict that the thermohaline circulation will weaken and that the surface waters will freshen poleward of mid-latitudes, and become saltier in the extratropical regions. In addition, the predicted warming of surface waters is latitude-dependent, with the Southern Ocean initially tending to warm...

Ocean Surface Water Mass Transformation

George Nurser Ocean water mass characteristics are set by direct contact with the atmosphere and subsequent transport and mixing in the ocean interior. Section 5 deals with these interior processes, including the conservative mixing of heat and salt to produce water masses of intermediate densities. Lazier et al. (Chapter 5.5) discuss changes in surface water mass properties that influence the deeper layers, which become an essential part of the global thermohaline...

Ocean Circulation And Climate Isbn 0126413517

Copyright 2001 Academic Press All rights of reproduction in any form reserved Fig. 4.5.1 The scheme for the circulation of the abyss by Stommel (1958) as driven by two isolated sinking regions at the poles and uniform upwelling over the rest of the globe. Fig. 4.5.1 The scheme for the circulation of the abyss by Stommel (1958) as driven by two isolated sinking regions at the poles and uniform upwelling over the rest of the globe. focused, instead, on a small region of the South Atlantic - the...

Harry L Bryden and Shiro Imawaki

The earth is heated by solar short-wave radiation, which falls predominantly in tropical regions, and is cooled by outgoing long-wave (black-body) radiation, which is reasonably uniform over the globe (Fig. 6.1.1). Satellite measurements at the top of the atmosphere show that the net incoming short-wave radiation from the sun exceeds the outgoing long-wave radiation back to space for latitudes equatorward of about 35 , so that tropical and subtropical regions gain heat from space. Poleward of...

Dic

OBSERVATION Analysis Sarmiento et al. 1995 OBSERVATION Analysis (Only DIC Transports) Holfort et al. 1998 Fig. 6.3.13 Comparison of present-day and preindustrial carbon budgets (in PgCyr-1) for the North and Equatorial Atlantic as summarized by Sarmiento et al. (1995) and this study based on the transport calculations of Holfort et al. (1998). DIC stands for dissolved inorganic carbon and is identical to TCO2. DOC stands for dissolved organic carbon. (a) The Sarmiento et al. (1995) model...

Zhengyu Liu and S G H Philander

4.4.1 The role of diffusion and advection The salient feature of the thermal structure of the ocean is the thermocline, which is particularly sharp and shallow in low latitudes. The processes that maintain the thermocline are presently of considerable interest because those processes appear to be of central importance to interdecadal climate variability and global climate changes (Cane et al., 1997 Gu and Philander, 1997 Liu, 1998 Zhang et al., 1998a). The first studies of the thermocline were...

OOPC Ocean Observations Panel for Climate

1997 Report of the International Sea Level Workshop. NOAA (and as GCOS Report No. 43, GOOS Report No. 55 and ICPO Report No. 16), 133 pp. 7.4 OOPC (Ocean Observing System Development Panel), 1993 Interim Design for the Ocean Component of the Global Climate Observing System. Texas A& M University, College Station, TX, 105 pp. 7.4 OOPC (Ocean Observing System Development Panel), 1995 Scientific Design for the Common Module of the Global Ocean Observing System and the Global Climate Observing...

The annual cycle

The annual cycle is a major component of the large-scale variability over most of the ocean. It is caused by a combination of many different processes and hence exhibits a very complicated geographic pattern in its amplitude and phase. Owing to its dense spatial coverage, satellite altimetry provides the first detailed description of this complicated pattern. Jacobs et al. (1992) presented the first results of the global ocean annual cycle from altimetry using the GEOSAT data. The analysis was...

Tropical Kelvin and Rossby waves

Large-scale low-frequency oceanic waves play a key role in the dynamics of the tropical ocean and its interaction with the atmosphere. These waves are essentially driven by winds, but the overlying winds are also affected by the waves through air-sea coupling mechanisms. The interplay of baro-clinic Kelvin waves and Rossby waves has been proposed to be an important mechanism for sustaining the semioscillatory behaviour of ENSO in the delayed-action-oscillator theory (Battisti, 1988 Schopf and...

Freshening of NPIW and AAIW

The two intermediate waters, NPIW and AAIW, which originate respectively in the sub-polar North Pacific (Warner et al., 1996) and in the Southern Ocean, have similar roles in ventilating the intermediate depths of the Pacific Ocean. NPIW is of much smaller volume and is confined to the North Pacific, while AAIW can be found in the Atlantic, Indian and Pacific Oceans. Both of these water masses are characterized by a salinity minimum. To identify any change in their properties, six WOCE...

Spinup of the North Atlantic gyre circulation

From the subtropics northwards over the northern North Atlantic and Nordic Seas, the status of the marine environment during WOCE is overwhelmingly determined by the extreme long-term behaviour of the NAO. As described earlier (Section 7.3.2.2), the WOCE field phase occurred at a most unusual interval in the climatic history of the North Atlantic, at the end of a period in which the principal atmospheric forcing mode in that sector had amplified over three or four decades to its most extreme...

Summary and conclusions

The one-time survey was a success in achieving global coverage, meeting its requirements on sampling accuracy of the basic hydrography, documenting methods used at sea and ashore and educating a generation of hydrographers to achieve the above in the face of a heavy seagoing schedule, which strained personnel and logistics. Advances in the use and exploitation of ADCPs during the WOCE observational period were enormous. Data quality from shipboard ADCPs improved by an order of magnitude,...

Subgridscale parameterizations

Perhaps the most pressing concern, particularly for global climate modelling on non-eddy-resolving grids, is the improvement of parameterizations for 'sub-grid-scale' processes. For coupled climate models with typical grid spacing of several hundred kilometres, these processes encompass all of the energetic mesoscale variability, as well as many sub-basin-scale thermodynamic processes such as dense overflows, deep convection and diapycnal mixing processes in boundary layers and in the ocean...

Determining currents in the ocean

Because the ocean is practically opaque to all but acoustic radiation, knowledge of its motion below the surface is sporadic and gained at great effort. Most of what we know about the ocean's circulation is based not on actual velocity observations but rather on hydrographic measurements. These measurements of water properties are used in two ways. Temperature and salinity are used to calculate density that, according to the geostrophic relation, determines the vertical variations (shear) of...

Interaction between eddies and mean flow

Spatial variability of the eddy Reynolds stress allows the study of the interaction between eddies and mean flow. Using only 1 year's worth of GEOSAT data, Tai and White (1990) showed some very interesting patterns of Reynolds stress convergence that suggested that the Kuroshio Extension was accelerated by a convergence of eddy momentum flux, while the mean flow was decelerated by a divergence to the north and south of the current. This finding is consistent with theoretical ideas of the growth...

The ocean general circulation

In the open ocean a few hundred km away from the equator, the large-scale oceanic flows are nearly in geostrophic and hydrostatic balance, leading to the integral form of the 'thermal wind' equation for the horizontal velocity at depth z where z0 is a reference level for the integration and v0 is the velocity at the reference level, p is the density of seawater, g is the earth's gravity acceleration, f is the Coriolis parameter defined as f 2ft sinwhere ft is the earth's rotation rate (7.292 x...

Interocean Exchange

Earth's climate, responding to the different thermodynamic properties of the land and ocean surfaces, is sensitive to the continental configuration and distribution of mountain ranges. This is clearly seen in the pattern of mean annual and seasonal range in such climate parameters as temperature and humidity and in the quasistationary patterns of atmospheric circulation, from small-scale sea breezes to planetary waves. Presumably because of the ocean-land configuration, each ocean basin is...

WCRP World Climate Research Programme

Prepared by the CLIVAR Scientific Steering Group, August 1995. World Climate Research Programme, WMO TD-No. 690, 157 pp. 7.4 WCRP (World Climate Research Programme), 1995b Comparison of TOGA tropical Pacific Ocean model simulations with the WOCE TOGA surface velocity programme drifter data set. Report Assembled by the Global Drifter Center and edited by WMO, June 1995. WCRP-No. 4 1995, 156 pp. 4.1 WCRP (World Climate Research Programme), 1998 CLIVAR Initial...

Applications how are SADCP and LADCP measurements changing our view of ocean currents and physics

The scientific role of ADCP observations is a function of their strengths and weaknesses relative to other types of observations. The main strengths are 1 measurement of absolute current profiles, in contrast with geostrophic profiles, which are always relative to an unknown reference 2 high horizontal and vertical resolution 3 measurement of both velocity components, also in contrast to geostrophic sections 4 low marginal cost, leading to a large data set. 1 accuracy limitations, particularly...

Estimation of current transport and variability

The temporal variability of the transport of surface currents can be readily determined from the difference in altimetric sea-surface-height anomalies (with temporal mean removed) across the domain of the current (Zlotnicki, 1991). Determination of the absolute velocity and transport of currents and eddies is problematic because the knowledge of the geoid at the mesoscale is not sufficiently accurate for oceanographic applications. Significant effort has been made to construct local geoid...

T

Fig. 4.1.3 Schematic of SVP drifter. mounted on the upper portion. When the drogue was attached the surface float submerged often no submergence was observed when the drogue was detached. These drifters weighed about 24 kg when packed into biodegradable cardboard boxes that served also as deployment packages. When the drifters were deployed at sea, the transmitter emitted a 0.5-watt signal at 401.65 MHz, approximately every minute. This broadcast contained a...

Yz y

The essential feature of this Temporal-Residual-Mean (TRM) approach to the density equation is that it shows that the relevant three-dimensional density flux, namely the modified density flux, FM, can be decomposed into a non-divergent flux and a flux that is directed along the density surfaces, AVy. Moreover, this skew flux can be represented in the conservation equation as an extra advecting velocity (together with a different nondivergent flux). It can be shown that this same extra advecting...

Gf 9 8 7 6 5 4 3 2

Section 1 plates appear between pages 44 and 45 1.1.1 WOCE and the World Climate Research Programme 3 1.1.2 The scientific approach to the complex climate system 4 1.1.3 Ocean-atmosphere interaction and climate 5 1.1.4 Rapid changes related to the oceans 6 1.1.5 Cryosphere and the oceans 7 1.1.6 Anthropogenic climate change and the oceans 7 1.1.7 Future climate research and ocean observing systems 8 1.2 Ocean Processes and Climate Phenomena 11 Allyn Clarke, John Church and John Gould 1.2.1 A...

The WOCE Float Programme

There was, at the start of WOCE, great optimism that inverse analyses based on conserving transport of tracer water properties measured in the WOCE Hydrographic Programme could accurately estimate the absolute mean velocity of the general circulation. But for two reasons it was felt that direct observations of absolute subsurface flow should be included in the measurement programme. First, the precision that could be achieved by inverse analysis procedures was uncertain, but it was clear that...

Spacetime scales of ocean processes and models

The temporal and spatial scales of oceanic motions extend over many decades. A frequency-wave-number diagram is a convenient way to summarize scales of processes, even though it constitutes a linear view of a non-linear system and hence is necessarily limited in its interpretation. Figure 7.2.1 indicates the temporal and spatial scales of several relevant ocean processes. Also shown are the dispersion curves for gravity and planetary waves, in each case barotropic, and the first four baroclinic...

J S Godfrey G CJohnson MJ McPhaden G Reverdin and Susan EWijffels

Equatorial Wind Stress And Ocean Current

4.3.1 Flow and water mass transformation patterns Most of the heat absorption into the global oceans, and much of the freshwater absorption, occurs in the tropics. Furthermore, Sea Surface Temperature (SST) is sufficiently high in the tropics that deep atmospheric convection can and does occur over it. Movements of deep convection patterns, which affect climate globally, depend sensitively on small changes in SST. Thus it is critically important for the improvement of global climate models that...

How the WHP defined standards for data and methods of measurement

The measurement techniques required for WOCE had been built up over a long period of time. But at the start of WOCE there were many parameters for which only a few groups in the world had the expertise to measure them to the required standard. Never before had a single coordinated hydro-graphic survey planned to draw on contributions from so many different institutions, investigators and countries. The question therefore arose of how to ensure that data were of a uniformly high standard,...

Horizontal Distribution Of Ocean Current

Ekman Pumping

Fig. 5.3.1 (a) T S diagram from Iselin (1939) showing the T S relationship along the sea surface in winter in the western North Atlantic (open squares) and at depth (the solid line labelled Sargasso Sea) and along the sea surface in winter in the central North Atlantic (open circles) and at depth (the solid line labelled Eastern North Atlantic). Note that the surface and subsurface T S relationships are similar over only a small portion of the total temperature range shown. (b) T S diagram from...

Lowered ADCP systems

Although the LADCP and SADCP systems and algorithms are similar in many ways, there are some important differences relevant to LAD CP profile errors the LADCP depends much more critically on the inherent accuracy of the sonar. It is important to distinguish between the accuracy of the relative velocity profile as a function of vertical wavenumber, and the accuracy of the depth-averaged velocity - their error sources and characteristics are nearly independent. One must also distinguish...

Peter M Saunders

The deep and abyssal waters of the global ocean are produced at near-polar latitudes by the intense cooling of winter storms. The waters convect downwards and spread slowly equatorward, renewing the deepest and most distant layers of the global ocean on a time scale of several hundred years. In the south convection carries such water from the fringes of the Antarctic continent directly to great depths, particularly in the Weddell and Ross Seas. In the north, because of the topography of the...

DJWebb and N Suginohara

4.2.1 Processes in the ocean interior In this chapter we concentrate on the interior circulation of the ocean away from the equator and, for the most part, away from all boundaries. We will also generally concentrate on flows at scales larger than the Rossby radius. Our present knowledge about such flows comes from a mixture of hard in-situ observations and shrewd theoretical analysis. This combination works best in the top kilometre of the ocean where current velocities are relatively large....

Peter Niiler

Through many centuries mariners have observed ocean surface currents by noting how their vessels drift, and cartographers have prepared maps on the basis of these ship-drift reports. Instrumental observations of ocean currents on a global basis began about 115 years ago during the voyage of HMS Challenger. She left Portsmouth, England, on 21 December 1872, on an ocean expedition that was to navigate the globe in three and a half years. The measurements of the state of the ocean at 354 stations...

Nelson G Hogg

4.5.1 Deep circulation in the framework of WOCE During the design phase of the World Ocean Circulation Experiment (WOCE) it was recognized that various strategies were needed to 'divide and conquer' the massive problem of making a significant step forward in our understanding of the global circulation. One of these was a series of 'subject' meetings to contrast with the earlier 'sector' meetings at which different ocean basins had been the topic. One such meeting was held at Woods Hole in 1986...

Vertical coordinate systems

The choice of the vertical discretization is of particular importance for ocean circulation models. Currently, a variety of forms are used. Among these are models featuring alternative treatments of topography and the vertical coordinate. Examples include vertical coordinate systems based upon geopotential levels, isopycnal layers, and topography-following ('sigma') surfaces. While the first of these approaches is still the most prevalent, all three have by now been applied successfully to...

Extratropical Rossby waves

Westward propagation is a ubiquitous characteristic in a display of sea-level anomalies with a time-longitude section except within the vicinity of the equator (Fig. 3.3.7, see Plate 3.3.7, p. 172). Its interpretation in terms of Rossby waves has been documented in a large body of literature (Fu and Chelton, 2000). Identification of the source of these waves is not easy, but they are to a large extent forced by wind remotely. Because of the variability of the sea surface temperature associated...