Ivanov Yu.A

Report of a chief of an expedition

1.	Introduction.

In the 31st cruise at RV "Professor Shtockman" hydrophysical studies were carried out 
in a north-east part of the Atlantic ocean in a zone of the Azor front. The expedition route 
scheme and the works area are given on Figure 1.

The expedition took place within the international WOCE program, basic project 3, part 
"subduction" of projects "Fronts and eddies" and "Razrezy" of the Russian state 
scientific - technic program. "Complex Research of Oceans and Seas, of the Arctics and 
Antarctic".


1.	Subduction.

As a term of subduction there is understood a set of physical processes which 
determine the input of waters of a surface boundary layer being directly influenced by the 
atmospheric effect into the upper part of a main thermocline. The idea of the water 
masses being formed in the inner ocean area by the way of intrusion and "ageing" of the 
surface layer waters was first brought up by the end of the 30s by Aiselin and 
Montgomary on a base of the joint analysis of vertical and horizontal T-S curves for the 
ocean surface and as a result of this their principal similarity has been shown. 
Practically up to the latest time this idea had neither experimental nor theoretical 
development. Beginning with the 1985 mainly by russian as well as by foreign scientists 
there were taken measurements of thermohaline characteristics in the ocean with high 
vertical and horizontal resolution. One of those should be first considered the 
researches in the experiments "Mesopolygon" in 1985, "Megapolygon" in 1987 in the 
expedition "Atlantex-90" in 1990. As a result mesoscale intrusive formations with 
anomalous relatively to hum characteristics were found and described. It is shown that 
intrusions are statically steady formations which shift in quasi-isopicnic layers. Usually 
intrusive structures were found in the areas of hydrologic fronts.

Recently there appeared rather simple models where an exchange in the ocean is 
parameterized with isopychic and dynamic exchange differing from a traditional vertical 
and horizontal exchange. Results of modeling let us understand a number of problems 
solution of which is related to an understanding of subduction processes.

Nowadays an international program of subduction studies is formulated and carried out 
and it is a part of a general program "World ocean circulation experiment" (WOCE). 
Repeated researches of the specifics at subduction processes of different seasons are 
now carried out in the area of Azor front (AR-II). The Institute of Oceanology of Russ. 
Acad. Sci. participates in this program and provides this cruise partly covering its 
obligations.

2.	Fronts and eddies in the ocean.

In 1970 soviet scientists conducted a big experiment on research of hydrophysical fields 
of the open ocean-Atlantic hydrophysical polygon-70. Synoptic eddies of the open ocean 
were discovered and described in a result of repeated hydrophysical surveys and 
currents measurements analysis. This discovery stimulated intensive researches of the 
eddies activity in different regions of the ocean: american experiments MODE I, MODE II, 
soviet-american experiment POLYMODE, soviet experiments "Mesopolygon", 
"Megapolygon", "Atlantex-90" and other.

Study of experimental data and results of the eddy-resolution al modeling let us assume 
that ocean eddies, and first of all-frontal eddies may bring an important input into the 
exchange of heat, salt and momentum in the ocean. According to this nowadays there 
are taken active modeling and experimental research in different ocean regions for 
solution of this fundamental problem of the ocean physics.

3.	Main goals of the expedition.

3.1. Taking measurements for description of the geographic location and intensity of 
the Azor current and of the Azor frontal zone, of meanders and eddies forming due 
to hydrodynamic instability of a current. Types of measurements: continuous 
temperature measurements in the near-the-surface ocean layer; discrete sound 
measurements on a hydrophysical survey of the research region; measurements 
of currents on ABC in the Azor current rod (programs "WOCE", "Fronts and eddies").

3.2.	Taking measurements for study of subduction processes of surface layer waters 
and the intermediate waters ventilation in the zone of the Azor front. Types of 
measurement: temperature and salinity measurement with high spatial resolution 
(horizontal 0,5 -1 km, vertical 0,2-1 m) in the upper 400 meter ocean layer; 
microstructural measurements of the vertical distribution of temperature, salinity 
and vertical current shift in a layer of 0-300m; CTD-sounding up to a length of 
2000m (program "WOCE", part "Subduction").

3.3.	Measurements for description of structure and dynamics of the upper ocean level. 
Types of measurements: repeated drift measurements of temperature and salinity 
profiles with discreteness of 3 hours during 36 hours; measurements of currents 
velocity in the upper quasi homogeneous layer and seasonal thermocline with 
discreteness of 28 sec.; measurements of microstructure of vertical distribution of 
temperature , salinity and velocity gradient of the horizontal current component 
(programs "WOCE", "RAZREZY").

3.4.	CTD-sounding on a special program in case of finding lenses of mediterranean 
origin for description of thermohaline structure in a "body" of the lens and in its 
periphery )Program "WOCE", "Fronts and eddies").


4.	Methods and means of measurement and data processing.

Metrological supply of measurement equipment.

For description of a large scale structure and a synoptic scale disturbance there was 
undertaken a CTD-survey in 4 sections, oriented normally to the Azor front. Distance 
between the sections-60 miles, and measurement discreteness on sections 10-20 
miles. CTD-sounder "Mark-3" has been used for measurements.

Mesoscale structure measurements in a frontal area were taken on transfrontal 
sections by the way of tugging at a speed of 4 knots of CTD-sounder with the depth 
scanning. That provided a high measurement resolution as to horizon (discreteness < 
900 meters). Scanning CTD-complex "Fish" with a measurement sounder modulus 
"Mark-3" on tug has been used for measurement.

Microstructural measurements were taken at a daily station with discreteness of 3 hours 
up to the depth of 250 meter. Measurements were taken by a falling microstructural 
sounder "Baklan" with two sensors of velocity, conductivity, temperature, pressure and 
vibration.

At the same daily station there were taken current velocities from aboard of a ship in the 
upper ocean layer and vertical profiles of temperature and salinity. Measurements were 
taken from aboard of a ship by current meters "POTOK" with a time discreteness of 38 
sec. at 10 horizons and OHS -sounder (optical hydrophysical sounder constructed by 
SKB MHI) every three hours.

Mentioned above the measuring complex at a daily station was undertaken, m order to 
describe the dynamic and thermohaline-structure of the upper boundary layer and its 
daily evolution.

Processing of sounders "Mark-3", OHS and current meters - "POTOK" was provided 
according to standard algorithms. Program maintenance of the registration and 
processing of the tugged complex "Fish" was provided by employees of the Atlantic 
division: engineer-programmer V.A.Maslov; senior scientist Dr. N.N.Golenko.

Meteorologic measurements were taken at standard terms 4-times a day. During 
polygon works meteorologic measurements were carried out every 3 hours. Measuring 
complex included standard equipment: thermometer for the air temperature 
measurement, psychrometer, thermometer for the water temperature measurement, 
aneroid barometer.

Standard processing of meteorologic information and calculation estimation of heat, 
humidity and momentum fluxes was provided by GGO methodic. Operative facsimile 
synoptic maps and ocean surface temperature maps were received and analyzed.

Metrologic maintenance of measuring equipment is given in the metrologic commission 
act (the act is supplemented to the expedition report).
5.	Estimation of the technical state and of the scientific

Equipment usage during the cruise.

The ship's echo sounder acts unstably and only on drift. Under condition of sharp 
changes of the bottom relief the signal practically is not registered. That made 
considerably difficult the installation of two ABC. That was the reason of a decision to 
stop the following settlement of the anchored autonomous stations.

CTD-sounder of the company "Neil Brown" - "Mark-3" was used in a regime of 
measurement on drift and a regime of scanning in hydrophysical complex "Fish". The 
sounder was working without failure during measurement taking on drift. During the 
work in the scanning regime there were malfunctions in the connection lines due to the 
winch collector corrosion. Another type of malfunction happened due to occasional 
plankton ingress into the conduction sell (despite of the special protection grid). In case 
of detecting of deviation in the conductivity data the sounder has been upraised and the 
sell was washed by the fresh water. Usually malfunctions have been removed during 
the data processing without considerable information loss.

Continuous measurements by the complex "Fish" were few times disconnected due to 
blocks break. Blocks pulley has been split and needed to be changed because of bad 
slip under high load. For normal functioning of this complex it is necessary to use 
blocks fitted for a high load with pendulum bearings.

Technical state of the sounder "Baklan" did not allow to use it for work on each station 
as it has been supposed to do. Wear of the cable line, corroded collector, damages of 
the sounders body anodic surface often brought to breaks and loss of information. That 
is why it was necessary to repeat the sounding.

22 velocity and temperature meters "Potok" (6-on ABC-1, 6-on ABC-2 and 10 in string) 
were used.

Result: - One "Potok" on ABC-1 went out of order because of instable work of the quart 
generator (the instrument has fallen down on the metal deck at the moment of 
installation).

€	four instruments had small angle of turn of tape pulling of the magnetic information 
terminal during 1 record cycle (though not all the information has been last);

€	one instrument (on ABC-2) has been flowed. (The reason is so far not clear).

Two opticohydrophysical sounders MHI 4112(OFA) were testified in the expedition 
conditions.

There were dane 7 soundings by each complex at different depths up to 3500 m (the 
limit of the cable length).
Result: 

1.	Functioning of complexes satisfactory: sounders measuring pressure, 
temperature, conductivity attenuation indicator of directed light (measurement error 
satisfies the passport data).

2.	The system of complexes switching of from power works unstably.

3.	Barometer operation system works unstably.

Out of a total amount of soundings two failed (there was a discharge of accumulators 
below the allowance level what made it impossible to pass the information to PC) a 1 
sounding (tester) brought to a loss of 5 barometers and a complete switch off of a 
reserve power what resulted in a loss of information.


List of the expedition participants.
Heading group.
------------------------------------------------------------
Group of technical supply.
1. Ivanov Yu.A.        Chief of expedition,         IORAN
   Doc.Phys.mat.sci.
2. Golenko N.N.        Dep.Chief of expedition,     AD IORAN
   Cand. Phys.mat.sci.
3. Nikolaeva A.A.      Scientific secretary         IORAN

Group of mathematic processing
1. Filyushkin Yu.B.    Chief of a group,            IORAN
   Cand. Phys.mat.sci.
2. Orlov V.S.          Scientist                    IORAN	
3. Meshyanov S.L.      Scientist,                   IORAN
   Cand. Phys.mat.sci.
4. Aleinik D.L.        Engineer I category          IORAN

Group of technical supply
1. Onofriychuk S.F.    Chief of a group             IORAN	
2. Kondrashev S.E.     Chief engineer,              IORAN
   Cand. Phys.mat.sci.
3. Pyaterenko S.A.     Electronics engineer         AD IORAN
4. Makeev N.G.         Labs. Worker                 AD IORAN

Group of measurement equipment.
1. Zarubin E.P.        Chief of a group             AD IORAN
2. Yakovlev E.A.       Major constructor            IORAN	
3. Podufalov A.P.      Engineerconstructor          AD IORAN
4. Arvan M.B.          Electronics engineer         AD IORAN
5. Doronin Yu.E.       Electronics engineer         AD IORAN

Group of physical processes.	
1. Maslov V.A.         Chief of a group             AD IORAN	
2. Koohl L.V.          Senior scientist,            AD IORAN
   Cand.geogr.sci.
3. Artemyeva T.S.      Metrology engineer           AD IORAN	
4. Prilyudko L.V.      Engineer                     AD IORAN	


7.	Research program course and detailed description of works 

Operation.

Arrived to a polygon on the 11 of October. 11-17 October there was carried a 
hydrophysical survey for determination of the Azor front and for description of the spatial 
structure of thermohaline fields. During the same period: 13 and 14 October in a front 
zone there were set up two autonomous buoys stations (topics 1-4 of the scientific 
program).

Mesoscale intrusive formations measurements were taken by the tugged hydrophysical 
complex "Fish" from 17-th up to 20-th October. The ABC N1 has been raised up on the 
19-th of October (topic 2 of the scientific program).

On the 20-21-st of October the daily station for the measurement of the upper ocean 
layer parameters was carried out. There were done: the daily measurements of currents 
(10 devices) on drift, OGF sounder measurements with discreteness of 3 hours; 
microstructural sounder "Baklan" measurements with 3 hours discreteness; 
meteorological measurements complex with the same discreteness (topic 2 of the 
scientific program).

The ABC N2 has been raised on the 21-st of October; measurements of the intrusive 
mesostructure in the area of the front were continues on 21-23-d of October (topic 2 of 
the scientific program).


8.	The volume of fulfilled works.

The extent of the expedition itinerary including the polygon works amounts to 4871 
miles. The amount of the accomplished stations 41.

The echolot measurement has been provided only on drift due to malfunction of the 
onboard echolot.

The total amount of the vertical sounding on drift by the sounder "Mark-3" and the 
sounder OGF - 50.

The amount of soundings by the hydrophysical complex "Fish" on drift 3-4 knots - 612.

Currents measurements on two mooring stations. On the N1 - 6 devices were working 
during 7 days, on the N2 - 6 devices were working during 8 days.

Measurements by the microstructural sounder "Baklan" - 10.

Measurements of currents on drift in the upper ocean layer during the 24 hours on 10 
levels.

The amount of standard meteorological measurements - 132.

The amount of received operative charts of hydrometeorological information - 250.


9.	Preliminary scientific results.

Interpretation of preliminary results of the data measurements analysis is presented in 
each part of the expedition scientific program. Schemes of stations dislocation on 
hydrophysical survey, of autonomous buoys stations, of daily drift station and of tugging 
of the "Fish" complex are shown on Figs 2a, 2b.


9.1. The Azor current and the frontal zone. 
	(projects: "Fronts and eddies", "WOCE", "Subduction", "Razrezy").

Currents computation and the hydrophysical fields analysis on the climatic massive 
data basis in the region between islands Madera and Azor indicate the existence of a 
weak current directed to the east [1,2]. Though the accomplish in this area of 
hydrophysical survey with high resolution (possibly started by expeditions Meteor, 1981, 
and Poseidon, 1982) allowed to find evident jet (streamed) current with corresponding 
to it frontal division. Kase and Siedler [3] and showed that this streamed current called 
Azor is an important part of the anticyclonic cycle of the North Atlantic the following 
researches showed that the Azor current considerably meanders and changes its 
location and intensity. Namely these specifics while averaging the data bring to 
considerable smoothing of hydrophysical and dynamic fields (results received from 
climatic data).

The up-to-data actual goals of the research of the Azor current and the jointed frontal 
zone should be considered the determination of the spatial characteristics of variability: 
transport of frontal zone and current m space, deviation and eddies formation 
strengthening and attenuation, interaction of the current with eddies.

The research of the frontal zones dynamic is closely connected with the problem of 
subduction as just in frontal zones, where isopychnic surfaces ascend to a seasonal 
thermocline and to an ocean surface, the subduction processes are even more 
intensive. The necessary condition of solution of this problems is taking of longterm or 
repeated measurements.

Region AR-XI of the international program WOCE is the object of detailed and repeated 
measurements, including the frontal zone of the Azor current for the research of the 
frontal zone dynamics and subduction processes.



Hydrophysical thermohaline structure of the frontal zone waters.

Polygon researches were began with the taking of the hydrophysical survey. The 
scheme of stations location is given on Fig.2a. As to the temperature and salinity the 
Azor front is definitely distinguished beginning practically with the ocean surface (Figs. 
3,4) by sharp strengthening of horizontal gradients across the front. Drop of temperature 
is 0,9 grades, of salinity 0,23 psu. The front width in the area of research changes from 
30 up to 70 miles. As to the distribution of density on the depth of 20 meters the font is 
not distinguished (Fig.5) what shows to the compensation of the temperature input to 
the density gradient by the salinity input which has the opposite sigh. On charts of 
temperature, salinity and density there are visible mesoscale and synoptic disturbances 
which are not always correlated. For example a cold stain on the east of polygon 
corresponds to a stain at sealed waters, but as to the salinity in this region there is no 
any specifics. On the other hand, in temperature distribution in the north-western part of 
polygon there is visible a stain of cold freshened waters, though in a field of density the 
anomaly in this region is not registered. Such incoherent structures in the upper layer 
are the result of unstationary atmosphere effect.

On the level of 100 m (Figs. 6,7,8) where direct influence of the atmospheric affect is 
shielded by thermocline there is evident a considerably close connection between 
distributions of temperature, salinity and density. Drop of temperature on the front is 1,2 
grades, salinity 0,24 psu The width is a little more than in near-the-surface layer. 
Besides the distinguishly expressed frontal zone on charts of characteristics distribution 
in the southeastern part of the polygon there are also observed the local formations of 
cyclonic and anticyclonic type (lower temperature, lower salinity and higher density 
cyclonic type; higher temperature, higher salinity and lower density anticyclonic type of 
distribution). The described character of the temperature, salinity and density 
distribution remains up to level of 600 meters (Figs. 9,10,11). Horizontal characteristics 
gradients decrease with depth. Anticyclonic and cyclonic type of characteristics 
distribution can be traced the same evidently easy up to that depth, though having 
different degree of definition. Thus the cyclonic type is slightly defined as to the density. 
Already at the depth at 500 meters there happens practically full compensation of 
density due to temperature and salinity disturbance. Complete destruction of the frontal 
structure of temperature distribution comes out at the level of 800 meters (Fig.12), at 
salinity at a depth of 700 meters (Fig.13), of density deeper than 1200 meters (Fig.14).

In eastern part at a polygon beginning with a depth of 700 meters considering 
temperature and 600 meters as to the salinity up to the depth of 2000 meters (the depth 
of measurements) there is evident a sharply distinguished abnormal structure with 
maximal horizontal size of 90 miles at a depth of 1000 meters (Figs. 15,- 16). Maximal 
positive anomalies of temperature and salinity are located at the same depth and are 
equal to 3 C and 0,6 .... relatively to hum. As to its thermohaline characteristics (12,0 C, 
36. 20 ... maximal values) this structural formation is related to lenses of mediterranean 
origin. It should be mentioner that according to our information lenses at such a fig size 
were so far not found in the ocean. Unfortunate a detailed measurement of the whole 
body of a lens could not have been done because of a lack of time.
Vertical structure of thermohaline fields. 

Vertical thermohaline structure of the Azor front zone is characterized by the following 
specifics: homogeneous upper layer, clearly distinguished during autumn seasonal 
thermocline, intermediate salinity maximum and destruction of the intermediate 
temperature maximum at the from crossing. On Fig.17 there are shown curves of 
vertical distribution of temperature, salinity and density measured at 80 miles to the 
north of the front. In a layer of 700-1300 meters there are detected intermediate 
maximum of temperature and salinity. As to thermohaline characteristics these waters 
should be related to the waters at the mediterranean origin. On Figs. 18,19,20 there is 
shown the destruction of the temperature maximum and partial wash-out of the salinity 
maximum in the intermediate layer at crossing of the frontal zone. After crossing of the 
frontal zone (Fig.20) the temperature maximum in the intermediate layer disappears, 
and the salinity maximum considerably decreases. Though, episodically mediterranean 
lenses cross the frontal zone without essential destruction. On Fig.21 there are shown 
distributions of temperature, salinity and density in a lens described above, based on 
the analysis of horizontal structure of hydrophysical fields. The vertical thermohaline 
structure of hydrophysical fields is more detailed characterized on T-S diagram. On 
Fig.22 there is given a specific T-S diagram for the first meridianal section at 
hydrophysical survey. In the upper part at the T-S diagram the T-S indexes at each 
station considerably differ, what is a specific character of distribution at the front 
crossing. On intermediate depths there is evidently observed a process of destruction of 
extreme characteristics at mediterranean waters in a zone of the Azor front. All of 
described specifics of vertical and horizontal structures of thermohaline fields in more 
detailed form could be analyzed by charts, sections, profiles with T-S curves gives in the 
atlas (supplement to the expedition report).


Waters circulation in the zone of the Azor front. 

Calculations of hydrophysical currents were done from two indication levels 1500 and 
2000 meters. Geopotential differences in the Azor current at all levels were invariable. 
Small deviations of geopotential anomalies at the level of 1500 meters are observed 
only in disturbances of the synoptic scale (see supplement). On Figs. 23-26 there are 
given charts of geopotential anomalies on four isobaric surfaces relatively to the 2000 
dbar surface. The Azor current has a stream character. The current width in the area at 
measurements in near-the-surface level (20 dbar) varies from 60 to 80 km. Maximum 
geostrophic velocity 35 sm/sec. Anticyclonic and cyclonic eddies are observed and 
traced up to the depths of 1000 meters in northwestern, south-western, southeastern 
and eastern part of the polygon. Anticyclonic eddy in a central-eastern part of a polygon 
is observed on all calculated levels up to a depth of 1800 meters. As it was already 
mentioned above this anticyclonic eddy in a layer of 600-1600 meters contains a water 
of mediterranean origin. The intensity of the Azor current decreases with the depth and 
at the level of 1200 meters the current geostrophic velocities are close to a zero. On 
Fig.27 there are shown velocity isolines on a second section at a hydrophysical survey, 
geostrophic rate of flow of a current is 15.6010 m /sec, what is 15 sv. On other sections 
this quantity practically does not change. Rate of flow calculations of 1500 -dbar and 
2000-dbar surfaces give the same result.

Measurements of the Azor current velocities accomplished at autonomous buoy station 
N2 on five levels are given in Table 1.

As it could be observed from a table, a direction of currents measured an ABC and 
calculated on geostrophic relations are close and velocities modules differ by values 
practically equal to the current velocity measured at a depth of 1200 meters on ABC. 
Thus the absolute current velocity at each level will be equal to the sum of the barocline 
geostrophic velocity and velocity measured at the depth of 1200 meters having a 
meaning of barotropic component. According to this the estimation of the absolute drain 
of the Azor current could be 25 sv.


Intrusive frontal subduction and ventilation of intermediate waters. 
(WOCE project III part "Subduction") 

Measurements according to the program "Subduction" were done by hydrophysical 
complex "Fish" up to the depth of 400 meters with resolution of 0.7 km as to a horizontal. 
There were carried and three sections parallel oriented to the frontal division. On Figs. 
28-30 there is shown the distribution of salinity, temperature and conventional density. 
Most evident the intrusive subduction is revealed on the right boundary (looking with the 
stream) of a frontal zone according to the salinity distribution, as most conservative 
characteristics. Well are observed "tongues" of more salted waters spreading in a front 
area from the surface layer to the upper part of the main thermocline. Background-
corrected to this structure there are observed intrusive spots with a scale of from 15 km 
up to 1.5 km. Above the frontal zone, below the seasonal shock layer there episodically 
appear intrusive formations of increased salinity. In temperature distribution in the front 
zone there are also observed the tongue-type formations spreading from the surface 
layer into the upper part of the main thermocline. Though there are not detected spots of 
the increased temperature. On a section at the conventional density in the area of the 
tongue-type formations of distribution of temperature, salinity and mesoscale structures 
of increased salinity there are observed only small isopycnal curves. On Fig.31 there is 
shown the salinity distribution according to data of hydrophysical complex "Fish" on the 
section 3. Here the "tongue" of the increased salinity is also observed on the right 
boundary of the frontal division. Intrusive formations are detected slightly, only to the 
north of the "tongue" there is revealed a well detectable sport of the increased salinity. 
Though, another particularity in the salinity distribution observed in this section is of 
great interest. Salted homogeneous waters of the surface layer located in the northern 
and central parts of a section when spreading to the south penetrate to a seasonal 
pycnocline and then (in its frontal zone and more intensively at its right boundary) 
descend into the upper part of the main thermocline.

Polygon works were accomplished during the autumn (October) when the buoyancy flow 
at the ocean surface is changing its sign. At that period there are considerably 
increased the portions of time when consolidation of upper ocean layer and deepening 
of lower boundary of quasi homogeneous layer take place. Tangential wind stress 
intensifies and correspondingly the Ekman excitation into a layer of seasonal 
thermocline. These processes determine the subduction intensification along quasi 
isopychic layers. Due to unstationarity of boundary conditions at the ocean surface the 
penetration of the surface layer waters into the seasonal thermocline may occur 
discretely, by separate portions. Here comes up a question: how does the salted waters 
transit across a picnocline into the upper part of the main thermocline (picnocline) 
execute. There could be assumed two physical mechanisms which are probably 
involved into this process: 1) incidental breaks of seasonal picnocline under the 
hydrodynamic unstability realization on the frontal division; 2) vertical convection caused 
by processes of double diffusion.

Ventilation of intermediate waters in the central and eastern parts of the north Atlantic 
proceeds to a considerable extend due to inflow of mediterranean waters. Because of 
considerable unstationarity of the flow the main portion of mediterranean waters is 
being spread in the ocean in the form of lens structures of anticyclonic rotation.

Carrying out of a hydrophysical survey succeeded in detecting of probably the biggest 
lens so far known by literature [4], and fragments of lens structures on 1-st and 2-nd 
section. Unfortunately the detailed measurements by the tugged complex "Fish" were 
possible to be done only in the area of a destroyed lens. On Fig.32 there are given 
distributions of temperature, salinity and density on section 4. On the section at a 
temperature distribution and even better on the section of a salinity distribution there are 
well observed the stains of waters with increased meanings of these characteristics 
which correspond to the meanings an the periphery of lens found by hydrophysical 
survey of section 4. On Fig.33 there are shown T-S curves of the lens periphery 
(st.1022), of intermediate area (st.1023) and at lens core (st.1024) and also T-S 
diagram for the 4-th section accomplished by "Fish" complex in a layer of 750-1050 
meters. T-S curve (st.1022) practically corresponds with T-S diagram in this layer. T-S 
characteristics in intermediate area of lens and in nucleus correspondingly increase. 
This circumstance let us assume that observed stains of saline and warm water 
appeared in result of destruction of the mediterranean lens (close by its characteristics 
to one observed in the polygon east) in the area of research.


Structure and dynamics of waters of the upper ocean layer 
(WOCE project and "Razrezy") 

Structure of the active layer at polygon was characterized by homogeneous layer, the 
width of which varied from 34 to 64 m, and by clearly expressed picnocline. In a western 
part of polygon the average depth of the mixed layer was 43 m, in eastern part 53 m. The 
homogeneous layer to the south of the front was an the average by 6 meters deeper.

During a period from 02hrs 00min 21.10.93 till 05 hrs 00 min 22.10.93 a daily drift 
station for research of characteristics of the upper ocean boundary layer was performed. 
Measurements of currents were done by devices "Potok" on levels 10, 13, 16, 20, 25, 30, 
40, 50, 70 and 80 m with time discreteness 52 see, of the vertical thermohaline 
structure by OGF-sounder, by microstructural sounder "Baklan" and 
hydrometeorological parameters (wind, pressure, ocean surface temperature, 
temperature of the air, humidity) with discreteness of 3 hours.

The average depth of homogeneous layer was 58 m. Amplitude of fluctuations of the 
lower boundary of homogeneous layer caused by internal gravitation waves did not 
exceed 10 meters and on the average equaled to 7 m. Weak wind (4-2 m/sec) and 
vigorous solar warming up permitted to observe building and destruction of daily 
thermocline. Thermocline started to build up at 11.00 and was observed up to 02.00 of 
the following day. At 05.00 the day thermocline completely destroyed as result of the 
night ocean cooling. Maximal temperature difference at the surface and at level of 10 m 
made up 1 C.

Analysis of currents measurements showed that within the upper homogeneous layer 
the current vector (modulus and direction) slightly varies (practically within the 
measurements accuracy). Below the thermocline the velocity vector often differs from 
currents of the upper mixed layer. That means that in the upper layer homogeneous as 
to its density the Ekman spiral is not formed, it should by though noted that relatively 
small wind velocities being present during the experiment could bring to rather big 
relative errors while measuring drift currents.


Hydrometeorologic researches. 

The specific character of the atmospheric circulation and of largescale processes was 
the meridian type at the air transport above the north Atlantic due to development of 
blocking processes in the ocean center.

During the period of 12-23 October the baric field in investigated area was anomalous: 
at a place of climatic center of the atmospheric effect at the Azor anticyclone there were 
present cyclones for 5 days and ridges of northern anticyclones for 7 days. The polar 
front was located southward at usual, behind the 40 n.l., waves generation processes in 
it brought to cyclogenesis within the area of tropical zone. In the research area there 
were predominating northern (21%) and south-eastern (18%) duration of the wind and 
velocities 5-10 m/sec (51%).

Turbulent fluxes of heat, moisture and momentum (tangential stress), calculated for 96 
observation terms at to the GGO methodics, varied correspondingly from 11 to 39 wt/m , 
from 6 to 302 wt/m , from 0.01 to 0.45 H/m . Average for 12 days meanings q, LE and t 
came correspondingly to 12; 127; 0,07. Turbulent heat fluxes, except of 5 situations, 
were directed from the ocean to the atmosphere. Heat expenditure for evaporation in all 
the cases directed to atmosphere exceeded averagely by 10 times the turbulent heat 
fluxes. Most vigorous turbulent exchange was 13, 15, 17 October and the lowest 21, 22, 
23 October.

Relations between the components of heat balance estimated by daily average values 
indicate that from 12 to 20 October the radiation balance was so small that even did not 
cover the heat expenditure for the turbulent exchange and the heat was coming up to the 
surface from lower ocean layers, 21-23 October at conditions of less clouds weather 
and weak turbulent exchange the solar radiation heat excess was transferred from the 
surface to lower layers, altogether during the whole period of research the heat was 
coming up the ocean surface from two sources: as a solar radiation (81wt/m , 58% of 
income) and from the ocean (58wt/m , 42% of income). From the ocean surface the heat 
was going away as fluxes of evident heat (13wt/m , 9% of expenditure) and of latent heat 
(127wt/m , 91% of expenditure).


17.	Summary of preliminary scientific 

Results of the cruise. 

Main expedition goals, formulated in the scientific program of the 31-st cruise of RV 
"Professor Shtokman" according to the international WOCE program, the base project 3 
and national project "Fronts and eddies", were accomplished.

1. The Azor frontal zone, the Azor current, meanders and eddies. 
	(Project "Fronts and eddies" and base project 3 of the program WOCE).

Hydrophysical survey of the Azor front was performed. The exact location of the Azor front 
and connected to it frontal zone was determined on the basis of processing and 
analysis of measurement data. Thermohaline structure of hydrophysical fields is 
described. Geostrophic field of velocity of the Azor current and eddies was calculated. 
The estimation of geostrophic expenditure of the Azor current was done and it equaled 
to 15,5010 m /sec.

In the Azor current bar there were set up two autonomous buoy stations with current 
meters. As a result of analysis it was established that the Azor current has a 
considerable barotropic component. With considering of the barotropic component the 
estimation of the total current expenditure comes to 25.0010 m sec. It should be noted 
that the estimation of total currents expenditure by instrumental data has been done for 
the first time.

2. Subduction processes in the Azor frontal zone and ventilation of intermediate 
and deep waters. 
	(Base project 3 of program WOCE).

The tugged complex "Fish" executed three tacks crossing the frontal zone of the Azor 
current. As a result there were received three transfrontal sections of the temperature 
and salinity distributions in a width of 0-400 meters with high horizontal (0.7 km) and 
vertical (20 sm) resolution. Processing and analysis of these data allowed to describe 
the two physical mechanisms of subduction process: a) localfrontal subduction which 
can be related with hydrodynamic inhomogeneity of gravitation waves in seasonal 
thermocline and convection processes caused by double diffusion; b) penetration of 
surface waters into seasonal thermocline in the area to the north at front and there 
spreading in thermocline "body" up to a frontal zone where they episodically break 
thermocline as a result of effect of the above described mechanisms. Due to 
unstationarity of boundary conditions and instability processes realization the 
thermocline break is often accompanied by generating at mesostructural intrusions 
formations.

For research at waters ventilation at intermediate depths the data of three tacks (4-th 
and 6-th), were taken by complex "Rybka" in a layer of 750-1050 m. It is shown that at 
these depths there are present "young" mediterranean waters with higher salinity and 
temperature in a form of lens and at "fragments" of lens structures.

3.	Structure and dynamics of upper active layer of the ocean. 
	(Program WOCE, project 3, "Razrezy").

For analysis of structure and dynamics of the upper ocean layer there were used data at 
hydrophysical survey measurement and complex of measurements from diurnal drift 
station (currents of 10 levels with discreteness of 52 sec., profiles of temperature and 
salinity, temperature pulsations, electric conduction and velocity shift, meteorologic 
changes each 3 hours). There are given variability characteristics of the upper layer 
parameters in space and in time. It is shown that in a layer homogeneous for its density 
the vector of drift current practically does not change with depth, namely the Ekman 
spiral is not formed in this layer.

4.	Interthermocline lenses of mediterranean origin
	(Project "Fronts and eddies", project 3 of WOCE program).

Under conducting of hydrophysical survey in the eastern part at a polygon there was 
found a large bus of mediterranean origin. The lens was 150 km in diameter and 
extended from 700 up to 2000 m by vertical. The lens was in a stage of destruction, what 
was evidenced by a considerable roughness of a lateral surface and inhomogeneity of 
temperature and salinity distribution in the lens nucleus. As to the survey data and "Fish" 
complex measurements in the width of 750-1050 m of the western part of polygon there 
were found "fragments" of lenses structures in a form of intrusive water stains with 
temperature and salinity meaning increased relatively to hum.

References 

1.	Interthermocline eddies in the ocean. P.P.Shirshov Institute of Oceanology, USSR 
Acad. Sci., 1986, Moscow, 142 p. (in Russ.). 2. Kase R.N., A.Siedler 1982. 
Meandering of the subtropicalfront southeast of Azores Nature. 300 (5889), 245-
246. 3. Leetmaa A., P.P.Niiler, H.Stommel 1977. Does the Sverdruprelation account 
for mid Atlantic circulation. Journal of Marine Research, 35, 1-10.

4.	Sarkisyan A.S., Demin Yu.L., Brekhovskikh A.L. and other 1986. Methods and 
results of calculation of the World Ocean circulation. Leningrad, Hydrometeoizdat, 
150 p. (in Russ.).
