Physical Oceanography, Vol. 14, No. 2, 2004
ANALYSIS OF OBSERVATIONS AND METHODS FOR CALCULATING
HYDROPHYSICAL FIELDS IN THE OCEAN
ANNUAL AND INTERDECADAL VARIABILITY OF THE AVAILABLE POTENTIAL
ENERGY IN THE BLACK SEA
A. M. Suvorov and I. G. Shokurova
On the basis of the climatic data array on temperature and salinity including the data of observa-
tions carried out at 102,000 oceanographic stations in 1910–1998, we estimate the amount of
available potential energy of large-scale processes in the 0–300-m layer of the Black Sea and stu-
dy its annual variability. The annual average amount of available potential energy in the active
0–300-m layer is equal to
13 5 10
. × J,
its maximum amount attained in March is 25 10
and its minimum amount attained in August is
× J . In the autumn–winter period, the den-
sity of available potential energy in the
0–50-m layer increases and its maximum is attained in
). Beginning with January, the density of available potential ener-
gy increases in the layer of the main pycnocline
m). Its maximum is attained in March
and then this quantity decreases till August (down to
). In August, we study
the interdecadal variability of the available potential energy in the 50–300-m layer by using the
data accumulated for decadal periods with five-year shifts in 1956–1995. The maximum vari-
ability is observed at a depth of
m. The maximum average (over the sea) amounts of availa-
ble potential energy were observed in 1961–1970 and 1986–1995. The minimum amounts were
recorded in 1976–1985.
The available potential energy (APE) of the ocean is defined as the difference between the sum of the inter-
nal (IE) and potential energies (PE) at any time and the minimum value of this quantity attained by the adiabatic
redistribution of liquid particles (with preservation of entropy) . In this case, the sum of the kinetic (KE), po-
tential, and internal energies remains constant. Note that the APE is a positive definite quantity. Its minimum is
attained in the state with stable stratification of density, horizontal isentropic surfaces, and constant pressure on
each of these surfaces . The available potential energy is actually a fraction of the total potential energy avail-
able for the transformation into the kinetic energy.
The concept of available potential energy was introduced by Margules in 1903 to explain separate storms.
In [3, 4], Lorenz applied this concept for the first time to the analysis of the general atmospheric circulation.
The kinetic, potential, and internal energies were regarded by Lorenz as the forms of energy playing signifi-
cant role in the processes of general circulation . The other forms of energy can be important for the local
processes but their transformation into the KE, PE, or IE in large amounts is impossible .
Lorenz demonstrated that the PE and IE increase and decrease simultaneously and, thus, can be regarded as
a single form of energy called (by Margules in 1903) the total potential energy (TPE). In what follows, the TPE
is split into the APE and the unavailable potential energy (UPE). The UPE is defined as the energy of a certain
Marine Hydrophysical Institute, Ukrainian Academy of Sciences, Sevastopol. Translated from Morskoi Gidrofizicheskii Zhurnal,
29–41, March–April, 2004. Original article submitted February 11, 2003; revision submitted February 24, 2003.
84 0928-5105/04/1402–0084 © 2004 Plenum Publishing Corporation