Vol.3, No.1, 69-74 (2011) Natural Science
Copyright © 2011 SciRes. OPEN ACCESS
Influence of solar eclipse on seawater
Sukumaran Santhosh Kumar1, Rethinassamy Rengaiyan2
1Department of Physics, Avvaiyar Government College for Women, U.T. of Puducherry, India; santhosh.physics@gmail.com
2Department of Physics, Aringar Anna Government Arts College, U.T. of Puducherry, India
Received 27 October 2010; revised 28 November 2010; accepted 30 November 2010.
Eclipse induced changes in solar radiation is a
common interest of scientists all over the world.
The disturbance of the heat balance along the
supersonic travel of the trajectory of the Moon’s
shadow could generate gravity waves during
solar eclipse, which results a reduction in the
concentration of ozone layer in the stratosphere.
We, in this context, conducted some experi-
ments to detect the possible radiations reaching
the surface of the earth and the impact of such
radiation in seawater during the recent total and
annular solar eclipses. This is the first time that
the variation in pH value of seawater during so-
lar eclipse is examined, and the experimental
data demonstrated that the solar eclipse phe-
nomenon affects the pH value of seawater due
to the shorter wavelength radiations received
on the surface of the earth. The reduction is
around 20% and 40% of the difference between
ordinary water and seawater during total and
annular eclipses respectively. The multidisci-
plinary influences of these findings are ad-
Keywords: Ozone Layer; Solar Radiation; Solar
Eclipse; Seawater; Marine Organisms
The solar eclipse being a rare natural phenomenon
gives an opportunity to investigate how the ionising ra-
diations react to the material surface of the earth due to
the fast solar radiation changes. A huge quantity of
shorter wavelength radiations are expected to reach the
earth’s surface during solar eclipse since the disturbance
of the heat balance along the supersonic travel of the
trajectory of the Moon’s shadow could generate eclipse-
induced gravity waves [1-4], which results a reduction in
the concentration of ozone layer in the stratosphere
[1,5-7]. Several measurements of solar radiation were
carried out since 1960; recent works [7,8] focussed on
the study of eclipse-induced changes in the spectral solar
irradiance at the earth’s surface, the effect of multiple
scattering on sky brightness, and the wavelength de-
pendence of the limb darkening effect etc.. The radia-
tions in shorter wavelengths (350 nm) are generally in-
fluenced more by the eclipse, and at large eclipse per-
centages (> 85%), it slowly decreases as the eclipse ap-
proaches its maximum [9,10] compared to that of the
longer wavelengths. Hence, one can expect shorter
wavelength radiations during partial eclipse, which is
less studied. The environmental effects of solar eclipse
had been mainly focussed on meteorological parameters
[11], photochemistry [12,13], boundary layer physics
[14], total columnar ozone [15], gravity waves [16], and
ionospheric parameters [17]. Zerefos et al. [7] pointed
out a characteristic artificial decrease of total ozone dur-
ing solar eclipse, which allows more radiations to pass
through. India had a total solar eclipse on 22 July 2009,
which was visible over the central India, while a partial
eclipse in southern part, and an annular eclipse on 15
January 2010, and this paper focuses on the study con-
ducted on sea water during these events.
The solar eclipse on 22 July 2009 was the largest total
solar eclipse in the 21st century, and which started with
sunrise. The path of the Moon’s umbral shadow on the
Sun began in India and crossed through Nepal, Bangla-
desh, Bhutan, Myanmar, China and ended in Pacific
Ocean. It was visible from 05:28 hrs to 07:40 hrs (IST)
and the maximum eclipse was at 06:08hrs. Other than
central India, a partial eclipse was seen. Karaikal, a dis-
trict of Union Territory of Puducherry located in the
latitude 10˚55' N and longitude 79˚52' E on the shore of
Bay of Bengal, had witnessed around 55% of the eclipse
at 06:08 hrs. The influence of solar eclipses on cloudi-
ness, i.e., ‘eclipse clouds’ [18], has been observed just
before the beginning of the eclipse and remains dissi-
pated up to the maximum eclipse period. This cloud
S. S. Kumar et al. / Natural Science 3 (2011) 69-74
Copyright © 2011 SciRes. OPEN ACCESS
structure prevailed during the eclipse occasionally ob-
scuring the solar disk, but the solar disk was visible
through lighter clouds during eclipse maximum. The
eclipse ended at 07:18 hrs with a high light intensity of
22550 Lux.
The solar eclipse on 15 January 2010 was the longest
annular solar eclipse of the millennium and the longest
until December 23, 3043. The eclipse started in the Cen-
tral African Republic, traversed Cameroon, DR Congo
and Uganda, passed through Nairobi, Kenya and passed
over the Indian Ocean, where it reached its greatest visi-
bility of magnitude 0.9190. At approximately 13.20 IST
the annular solar eclipse entered India at Thiruvanan-
thapauram (Kerala) and then at Rameswaram, (Tamil
Nadu). The study location, Karaikal is approximately
95.67 nautical miles from Rameswaram at which the
Moon’s umbral shadow reached the maximum around
98% of the annular position at 13:27 IST, and the eclipse
ended at 15:11 IST. The sky was clear throughout the
event, and hence, the eclipse maximum from 13:24 to
13:29, gave a dark effect of decrease in light intensity.
Kolev et al. [19] observed a continuous decrease in wind
speed without any significant change in direction during
the solar eclipse of 11 August 1999. Founda et al. [20]
also reported a similar effect of observations during the
solar eclipse 29 March 2006. As per the observations
recorded at Karaikal, there was a shift in wind direction
20˚ towards south (from 250˚ to 230˚ SW) but no change
in the wind speed. This shift in wind direction may be
mainly due to the change in pressure gradient force dur-
ing eclipse.
Emphasis was given on the response of seawater to
the abrupt change of the solar radiation by means of H+
ion activity during solar eclipse. This work also aims at
delineating the different types of radiations reaching the
earth’s surface and the possible effects on seawater.
Earlier studies on the ozone concentration reveal that
considerable reduction in ozone concentration during
partial eclipse [1] and total eclipse [5-7], which is the
major phenomenon for the observation of more radia-
tions of shorter wavelength on the earth. Many observa-
tional evidences on the formation and propagation of
eclipse-induced gravity waves at different atmospheric
heights [2-4,21-23] were reported. Zerefos et al. [24]
pointed out that the eclipse-induced cooling of the ozone
layer in the stratosphere is the main source of gravity
waves propagating both upwards and downwards.
Measurements of total column of ozone [9] using Brever
Spectrophotometers have revealed that there was a re-
duction of 30-40 DU total ozone on the day of eclipse,
29 March 2006, than the day before at Athens. Such a
reduction in surface O3 may be due to decreased effi-
ciency of the photochemical O3 formation [13].
The seawater from Bay of Bengal, the eastern coast of
India, was subjected in this study to find the influence of
solar radiation on the pH value under the exposed condi-
tion since major part of the earth is covered by sea. pH is
a measure of the acidity or alkalinity of a substance and
is one of the stable measurements in seawater. Ocean
water has an excellent buffering system with the interac-
tion of carbon dioxide and water so that it is generally
always at a pH of 7.5 to 8.5. In this context, a three stage
experiment is conducted: i) Sample at exposed condition
during solar eclipse, ii) normal days and iii) Sample at
non-exposed condition. Simultaneously, the changes in
the meteorological parameters are also recorded for bet-
ter understanding of other influencing parameters. Since
the said location had a partial eclipse on July 22, 2009,
we were able to detect the abrupt change of solar radia-
tion and its effect on sea water. The change in pH value
is recorded accurately with a calibrated pH meter con-
taining a glass electrode with temperature compensation
controls, from 05:30 hrs to 07:30 hrs (IST) continuously
on the day of eclipse and a few days prior to and after
the eclipse. The pH value of seawater recorded during
solar eclipse is compared with the corresponding time of
normal days.
During the annular eclipse on 15 January 2010, the pH
value of sea water was recorded well before the begin-
ning of the eclipse at 30 sec. resolution. The percentage
of solar disk covered by the moon’s umbral shadow was
calculated using a high resolution telescope with curved
grid lines. The meteorological factors like air tempera-
ture and the light intensity were recorded continuously
during the eclipse period.
A significant decrease in the pH value of seawater is
recorded on the total solar eclipse day, 22 July 2009,
when exposed to solar radiation during the eclipse period,
which reveals an increase in Hydrogen ion activity in
seawater. The change in pH value against time is plotted
in Figure 1, which reveals a considerable reduction of
20% of the difference between the pH value of normal
water and seawater.
On the day of annular eclipse, 15 January 2010, the
pH value is recorded well before the beginning of the
eclipse. The pH value started decreasing from its origi-
nal value an hour before the eclipse and reached its
maximum reduction when the moon’s umbral shadow on
the solar disc was 45% and when the eclipse percentage
was maximum, the decrease in pH value is minimum.
Another decrease in pH value was recorded again when
the solar disc was covered around 40% during the proc-
S. S. Kumar et al. / Natural Science 3 (2011) 69-74
Copyright © 2011 SciRes. OPEN ACCESS
ess of the end of the eclipse. Figure 2 reveals that the
average decrease in pH value from the normal day is
around 40% and that too at partial eclipse. The effect of
solar eclipse on radiation exists even before the begin-
ning of the eclipse and a drastic decrease in the pH value
is observed during partial maximum and it prolonged
even after the end of the eclipse. After an hour of the
eclipse, the sea water started regaining its original state.
This may be due to the fact that the influence of decrease
of shorter wavelength radiations as the eclipse approaches
its maximum compared to longer wavelengths. This is in
correlation with Tsanis et al. [6] that the solar radiation
started to increase after the eclipse totality, while the
surface ozone concentration started to increase about one
Figure 1. Comparison of solar radiation induced H+ ion activity in sea-
water during (a) normal day and (b) partial solar eclipse event on 22 July
2009. The reduction in pH value during eclipse is around 20% of the dif-
ference between the ordinary water (pH 7.5) and seawater (pH 8.5). The
vertical dotted line is the time of maximum eclipse occurrence, at which
the ionisation of seawater started due to the shorter wavelength rays reach-
ing the earth’s surface.
Figure 2. Variation of pH in seawater during (a) normal day and (b) annu-
lar solar eclipse under exposed condition on 15 January 2010 (dashed line
shows the % of eclipse; (+)symbol for approaching eclipse maximum and
(-)symbol for towards the end of process. (hrs refers IST).
S. S. Kumar et al. / Natural Science 3 (2011) 69-74
Copyright © 2011 SciRes. OPEN ACCESS
hour later and returned to its ordinary behaviour several
minutes after the end of the eclipse. A decrease in light
intensity (the total luminous flux incident on the earth’s
surface per unit area) of 10,000 Lux and a decrease in
surface air temperature of 6˚C are recorded during the
annular maximum.
Search for the reason of decreasing pH value per-
ceived the influence of ionising radiations reaching the
surface of earth during eclipse. Zhaobing et al. [25] ob-
served that irradiation of drinking water using gamma
rays reduces its pH value. During the partial solar eclipse
of October 1995, we have detected huge gamma counts
at the eclipse maximum by gamma ray spectrometric ex-
periments with NaI (Tl) scintillator. Since our measure-
ments show drastic decrease in pH value of seawater
during both the total eclipse event (partial at study loca-
tion) on 22 July 2009 and the annular solar eclipse on 15
January 2010, when exposed to solar radiation, in view
of the report of Zhaobing et al. [25], the reduction in pH
value is due to the shorter wavelength radiations reach-
ing the surface of the earth. By comparing our earlier
detection and measurements with the report of Zhaobing
et al. [25], it is obvious that among the shorter waves,
gamma rays influences more in the reduction of pH
value in seawater. These gamma rays are reaching the
earth’s atmosphere due to the gravity wave induced re-
duction in ozone concentration. The low energy gamma
rays ( 1.24 MeV) reaching the surface of the earth are
not passing through matter [26], as such these will not
penetrate deep into the sea instead are absorbed by the
upper layer of the seawater and the particles get excited.
Due to this absorption of energy the H+ ion in seawater
becomes more active, which decreases the pH value of
sea water. Due to the close association of pH value with
salinity, this reduction in pH value of seawater in the
surface layer during solar eclipse causes a critical change
in the behaviour of marine organisms that they move to
deeper region during this period. After few hours of the
eclipse event these organisms come to their normal be-
haviour since the seawater regains its original pH value
after an hour of the end of the eclipse. As per the report
of Sharma et al. [13] the change in meteorological pa-
rameters and the photochemical ozone formation during
eclipse are more or less similar to the behaviour of night
time chemistry [27].
Studies concerning behavioural changes of animals
have been performed mainly on vertebrates such as
fishes [28], birds [29], rodents [30], and chimbanzees
[31]. Diurnal fishes responded rapidly during total solar
eclipse and sought shelter in the reef [32]. The studies on
fresh water fishes during the 1980 solar eclipse in India
[28] reported that all species studied almost stopped
gulping air, became sluggish, and sheltered to the bottom,
and such changes during solar eclipse are related with
the activities appropriate for sunset. Hence this new
finding of reduction of pH during eclipse may provide a
new vision to the study of behavioural changes of ma-
rine organisms during eclipse, in the context of salin-
ity/pH value of seawater.
The decrease in pH value means reduction in salinity
of seawater and hence solar eclipse induced radiations
cause appreciable change in the freezing point of sea-
water, which may have an impact in the geophysical
studies of polar region.
During solar eclipse, reduction in ozone concentration
is formed because of gravity waves due to the change in
pressure gradient force. The ozone depression allows
ionizing radiation in addition to non-ionizing rays in the
short period of eclipse. These rays have a wide range of
effects on humans and aquatic and terrestrial ecosystems.
However the role of ionizing radiation during this proc-
ess, gamma rays, is less studied. Here, we report that, the
gamma rays are reaching the earth’s surface during
eclipse since the pH value of seawater is reduced when
exposed to solar radiation because gamma irradiation
reduces the pH value of water. It is to be noted here that
this observation is during eclipse partial maximum in
both the event of total and annular eclipses, in a costal
area; where the seawater influences the effect of eclipse,
especially on meteorological parameters. Our results are
the first one reported about the influence of gamma rays
during solar eclipse in the pH value of sea water. The
results discussed will probe a gateway to a new approach
of the behavioural studies of marine organisms in the
context of salinity or pH value during eclipse period and
may add an additional parameter in the geophysical
studies of polar region.
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