90
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
we assumed the average advection rate to be 4 cm s-l. It was also assumed that advection
occurs in all directions with equal probability. It has been established that up to 25% of heat
accumulated in the intermediate layer under the lens of freshened water can be transferred
directly to the surface by the time the fast ice edge becomes quasi-steady at the periphery of the
outflow zone. This results in a concentration of heat in the peripheral zone. The cumulative
effect of all vertical heat exchanges with the intermediate layer (in the regions of the peripheral
zone itself) amounts to, on average, 15.10 4 KJ m- 2 . This is equivalent to 47 cm of unformed
ice. The amount of heat transferred to the surface by isopycnic advection is twice as large as the
amount transferred to the surface via vertical heat exchange.
The heat which remained in the intermediate layer after vertical and quasi-horizontal heat
exchange was isopycnically transferred by horizontal advection beneath the periphery of the
freshened water zone. Here the double-diffusion heat exchange processes are extremely
efficient. Let us assume that, as shown above, the complete destruction of the intermediate
warm layer via intrusive stratification occurs even prior to the fast ice edge becoming quasisteady. Then the heat concentration beneath the periphery of the freshened zone can reach
26.104 KJ m-2 and more. This corresponds approximately to the lower estimate of the
possibility of a double-diffusion heat transfer to the surface (process 5+3, Figure 7). The upper
estimate was, as we recall, an order of magnitude greater.
The total heat transfer to the surface can reach 41.10 4 KJ m- 2 and more by the time the fast ice
edge becomes quasi-steady due to all acting processes: molecular and turbulent heat exchange,
salinity convection, double-diffusion, "quasi-horizontal" advection of warm intrusions to the
surface, horizontal advection of warm intrusions with "secondary" double-diffusion. This
would be equal to 129 cm of unformed ice (Figure 7). It is thus not surprising that, in the three
months after the onset of ice formation, the fast ice edge already becomes quasi-steady precisely
at the periphery of the zone freshened by river discharge.
Conclusions
Figure 7 presents a scheme that summarizes the possible heat exchange mechanisms between
the intermediate warm layer and the lower ice boundary. The diagrams above the scheme
present the estimates of heat exchange efficiency in cm of unformed ice for all processes under
study. A comparison with the actual observed ice cover types confirms our suggestions and
provides justification for the following conclusions.
1 Formation of the fast ice edge in the eastern Laptev Sea depends to a great extent on
processes determined by the spreading of river discharge. The quasi-steady position of the
fast ice edge is confined to the periphery of the transformed river water spreading, and is
governed by the large intensity of the heat exchange in this zone.
2 The fast ice edge is formed much further southward than the northern limit of the river
discharge spreading. River water rich in suspended matter is located within the zone of
drifting ice and the flaw polynya. Its incorporation into drifting ice intensively produced in
the po\ynya triggers a complex of processes usually referred to as the "Trans arctic ice
transport of river discharge".
Acknowledgements
This article is one result of 4 years of research and expedition studies under the RussianGerman Project "Laptev Sea System". The work of many Russian and German scientists in
various disciplines of natural science served as a basis for obtaining the results; the authors
express their most sincere gratitude to all of them. The results presented here could not have
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
we assumed the average advection rate to be 4 cm s-l. It was also assumed that advection
occurs in all directions with equal probability. It has been established that up to 25% of heat
accumulated in the intermediate layer under the lens of freshened water can be transferred
directly to the surface by the time the fast ice edge becomes quasi-steady at the periphery of the
outflow zone. This results in a concentration of heat in the peripheral zone. The cumulative
effect of all vertical heat exchanges with the intermediate layer (in the regions of the peripheral
zone itself) amounts to, on average, 15.10 4 KJ m- 2 . This is equivalent to 47 cm of unformed
ice. The amount of heat transferred to the surface by isopycnic advection is twice as large as the
amount transferred to the surface via vertical heat exchange.
The heat which remained in the intermediate layer after vertical and quasi-horizontal heat
exchange was isopycnically transferred by horizontal advection beneath the periphery of the
freshened water zone. Here the double-diffusion heat exchange processes are extremely
efficient. Let us assume that, as shown above, the complete destruction of the intermediate
warm layer via intrusive stratification occurs even prior to the fast ice edge becoming quasisteady. Then the heat concentration beneath the periphery of the freshened zone can reach
26.104 KJ m-2 and more. This corresponds approximately to the lower estimate of the
possibility of a double-diffusion heat transfer to the surface (process 5+3, Figure 7). The upper
estimate was, as we recall, an order of magnitude greater.
The total heat transfer to the surface can reach 41.10 4 KJ m- 2 and more by the time the fast ice
edge becomes quasi-steady due to all acting processes: molecular and turbulent heat exchange,
salinity convection, double-diffusion, "quasi-horizontal" advection of warm intrusions to the
surface, horizontal advection of warm intrusions with "secondary" double-diffusion. This
would be equal to 129 cm of unformed ice (Figure 7). It is thus not surprising that, in the three
months after the onset of ice formation, the fast ice edge already becomes quasi-steady precisely
at the periphery of the zone freshened by river discharge.
Conclusions
Figure 7 presents a scheme that summarizes the possible heat exchange mechanisms between
the intermediate warm layer and the lower ice boundary. The diagrams above the scheme
present the estimates of heat exchange efficiency in cm of unformed ice for all processes under
study. A comparison with the actual observed ice cover types confirms our suggestions and
provides justification for the following conclusions.
1 Formation of the fast ice edge in the eastern Laptev Sea depends to a great extent on
processes determined by the spreading of river discharge. The quasi-steady position of the
fast ice edge is confined to the periphery of the transformed river water spreading, and is
governed by the large intensity of the heat exchange in this zone.
2 The fast ice edge is formed much further southward than the northern limit of the river
discharge spreading. River water rich in suspended matter is located within the zone of
drifting ice and the flaw polynya. Its incorporation into drifting ice intensively produced in
the po\ynya triggers a complex of processes usually referred to as the "Trans arctic ice
transport of river discharge".
Acknowledgements
This article is one result of 4 years of research and expedition studies under the RussianGerman Project "Laptev Sea System". The work of many Russian and German scientists in
various disciplines of natural science served as a basis for obtaining the results; the authors
express their most sincere gratitude to all of them. The results presented here could not have