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Advances in Environmental Research 23: 207-221
© 2012 Nova Science Publishers, Inc.
POSSIBLE IMPACT OF DECREASING ARCTIC PACK
ICE ON THE HIGHER TROPHIC LEVELS –
SEABIRDS AND MARINE MAMMALS
Claude R. Joiris ∗
Laboratory for Polar Ecology (PolE), rue du Fodia 18,
B-1367 Ramillies, Belgium
ABSTRACT
Three main aspects of the possible impacts of retreating pack ice and changing ice
coverage in the European Arctic on the higher trophic levels are discussed in this chapter:
1. Seabirds are depending on their colonies on land during the breeding season; the
main species, e.g. little auk Alle alle, feed in mixed Polar/ Arctic Water in order to bring
back food (polar zooplankton) to their chicks on the nest. In case ice coverage is very
low, distance between colony and feeding grounds might become too long for such daily
trips, and little auks might have to interrupt breeding and massively leave their colonies
before the end of the reproduction cycle (e.g. on Jan Mayen in July 2005). On a longer
term, if ice coverage was decreasing too much in future years, the whole Spitzbergen
population might be affected, as well as other seabird species feeding mainly at the ice
edge.
2. Stocks of large whales were close to depletion in the north-eastern Atlantic due to
massive over-exploitation by whaling, and to their separation from the more abundant
North Pacific stocks by high ice coverage of both the North-East and North-West
Passages. In the frame of our long-term study of the at-sea distribution of seabirds and
marine mammals in Arctic seas from 1979 on, resulting in more than 10,000 half-an-hour
transect counts, an important increase of the north-eastern Atlantic stocks was detected
from 2007 on, the year with lowest ice coverage, mainly for bowhead Balaena mysticus,
blue whale Balaenoptera musculus, humpback whale Megaptera novaeangliae and fin
whale Balaenoptera physalus. Such a sudden and important increase cannot be attributed
to population growth, but to a probable inflow from the more abundant Pacific stocks, the
decrease of ice coverage allowing the opening of the Passages.
3. On the other hand, polar bear Ursus maritimus and its prey: pinnipeds - mainly
harp seal Pagophilus (Phoca) groenlandica - seem not to show any important decline of
their population, with a few local exceptions. Moreover, encountered bears regularly
concerned mother with cub(s), which also reflect the good health status of the population.
The reason is probably that they are not bound to pack ice as such, but to the Outer
Marginal Ice Zone (OMIZ): they are almost absent in the Closed Pack Ice (CPI). They
∗
E-mail: [email protected]
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Claude R. Joiris
seem to adapt and follow the OMIZ, even when its position is influenced by changes in
ice coverage.
These data collected on board icebreaking RV Polarstern are discussed in this
chapter, in function of changes in ice coverage, in the extent of the main water masses
and thus in the position of the ice edge and fronts.
INTRODUCTION
For a decade, ice coverage decrease in the polar marine domain - mainly the Arctic - is
attracting a lot of discussion and comments, both from part of the scientific community and
from the media (press, radio, television). Even if the main factor is probably a global change
with temperature increase, possibly due to human activities, divergent interpretations and
predictive models for future evolution were developed and applied. In this chapter, the aim is
first to define in some detail how Arctic pack ice is decreasing, and which mechanisms might
be involved. Then only, the possible long-term impact of this phenomenon on the higher
trophic levels - seabirds and marine mammals - will be brought up, using three examples
illustrating three main situations respectively: polar bear is often named as a species
threatened to disappear, since it is directly dependent on pack ice. Other comments will
concern cetaceans (whales) and seabirds, even if major changes are usually not expected for
these groups of species.
This work is part of a long-term study on the at-sea distribution of seabirds and marine
mammals started in 1974 (Joiris 1976) and continued during expeditions in the Norwegian
and Greenland seas on board different research vessels (RV Meteor, RV A. Dohrn, RV F.
Heincke, etc.). Since 1988, data were obtained from icebreaking RV Polarstern, i.e. including
pack ice, mainly on the 75°N and the 79°N transects between East Greenland and West
Spitzbergen, and resulted in 3,800 half-an-hour counts from 1988 to 1993 and 6,200 counts
from 2003 to 2010. A synopsis of seabird data for the period 1974-1993 (Joiris 2000) showed
that the little auk Alle alle is one of the most abundant species, together with the fulmar
Fulmarus glacialis, the kittiwake Rissa tridactyla and the Brünnich’s guillemot Uria lomvia
in the European Arctic seas (mainly the Norwegian and Greenland seas): together, these 4
species usually represent more than 90% of the total. The little auk represented the main
species in Polar Waters, at the ice edge and in closed pack ice, reaching more than 50% of all
bird species.
Data collected between 2003 and 2010 lead to the same conclusion. Important differences
occur between expeditions, mainly to be explained by differences in geographical coverage,
since their distribution is bound to the different water masses (Joiris 1978; Pocklington 1979)
as well as fronts, ice edge and eddies (Joiris and Falck 2010). Within a given expedition, the
extreme patchiness of animal distribution is reflected by the very high mean to median ratio
(non-normal distribution of the data). Both the low number of bird species - around 30 - and
the quantitative importance of a limited number of species are, as usual, the reflection of the
very low biodiversity of the polar marine ecosystems, mainly Arctic ones. Large cetacean
distribution is also strongly influenced by the presence of fronts (upwellings) (e.g. Joiris
2011); they used to be encountered at a very low frequency, but became more abundant since
2007.
Possible Impact of Decreasing Arctic Pack Ice on the Higher Trophic Levels
3
METHODS
Seabirds and marine mammals - cetaceans, pinnipeds and polar bear Ursus maritimus were recorded from the bridge of RV Polarstern (Figure 1) during transect counts, without
width limitation, lasting half-an-hour each. The reasons not to apply the method generally
used in monitoring routine programmes (transect width limited to 300 m, counting periods of
10 minutes) are: first, this method was developed for usual ships, i.e. with a bridge situated
around 5 m above sea level, while the bridge of Polarstern is situated at 18 m above sea level;
second: it was developed for regions with very high seabird density such as the north-western
North Sea off the coasts of Scotland, while the Arctic is characterised by very low densities
(it is not exceptional to register no bird at all in many counts); third: longer counting periods
help avoiding the wrong recording of followers such as fulmars Fulmarus glacialis, since
followers should only be recorded once per count; and finally, some species obviously cannot
be quantitatively detected as far as 300 m, such as alcids sitting on the water in general and
little auk Alle alle in particular, while larger seabird species such as gannet Sula bassana
clearly are detected at longer distances, not to mention the blow of blue whales detected at
more than 20 km (c. 10 nautical miles) in excellent visibility conditions. Anyway, there is no
science imposing a “compulsory” methodology, except in cases of routine studies, in order to
allow direct comparison among different teams. Even if it is obvious that the used methods do
influence the type of obtained results, from oxygen and BOD 5 determinations to bacterial
counts, chlorophyll determinations, zooplankton or fish sampling: it is not clear why some
specialist groups such as marine ornithologists and cetacean counters try to impose the same
method, … and regularly refuse to use and talk about studies based on another methodology!
Figure 1. Icebreaking RV Polarstern, AWI, Bremerhaven.
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Claude R. Joiris
Another aspect is that local birds, both sitting on the water or flying locally, can be
expressed as densities in the zone they belong to, while sometimes birds are massively flying
in a given direction: these do not really belong to the zone, but represent a flux and should not
be used for calculation of densities, but treated separately; the same being true of course for
migrating mammals.
The observations of water temperature and salinity derive from the continuous thermosalinometer registration system of RV Polarstern, water sampling taking place at a depth of
10 m. Local ice cover (%) was assessed by us from the bridge, medium-scale coverage
around Polarstern from the “Polar View” maps (University of Bremen, Germany:
http://iup.physik.uni-bremen.de:8084/amsr/Polarstern_visual.png), and large-scale coverage,
including its long-term evolution, from satellite images (National Snow and Ice Data Center,
Bounder, CO, USA: http://nsidc.org/data/seaice_index/ and NASA: in Wikipedia, The Free
Encyclopedia: en.wikipedia.org/wiki/Larsen_Ice_Shelf).
RESULTS AND DISCUSSION
1. The long-term evolution of pack ice coverage in the Arctic shows a significant decline,
and this phenomenon is of primordial ecological importance. It is limited to 0.25% per year in
winter and more marked in summer, with a maximal value of 1.2% per year (Figure 2a and
b). A quantitative example: the total ice covered surface in April was 14.2 million km2 in
2011, compared to a mean of 15 million km2 for the 1979 - 2000 period (NSIDC). This trend
is probably to be attributed to climate change and long-term temperature increase. Moreover,
very important year-to-year variations can be observed, with very low summer ice coverage
in 2005 - then the lowest ever recorded - and much lower even in 2007 (Figure 2). Such
events are very often interpreted as directly depending on temperature increase bringing the
melting of pack ice. They however cannot be directly attributed to climate change, per
definition a slow long-term phenomenon, so that important variations from one year to the
other cannot be attributed to climate change only, especially when ice coverage is increasing
again after one or two years of very low level.
Figure 2. Long term evolution of ice coverage in the Arctic (% per year for a given
month); a: example of late winter (March); b: example of late summer (September)
(NSIDC).
Possible Impact of Decreasing Arctic Pack Ice on the Higher Trophic Levels
5
They have to be explained by other mechanisms, not directly depending on temperature
changes, but are possibly indirect consequences such as abnormal wind direction and
strength, or changes in the extent of water masses. For example: when warmer Atlantic Water
is extending more northerly than usual in the Greenland and Norwegian seas, water
temperature and salinity are higher, and ice edge situated at a more northern position. Such
increases of water temperature are obviously not directly influenced by global change. These
year-to-year changes should not be extrapolated: the maximal decline is indeed 1% per year in
summer, not 10% per year as was sometimes suggested and written on the basis of the 2005
and 2007 data! Predictions about a complete disappearance of the Arctic pack ice within a
few decades, on the basis of 2005 and 2007 data, seem equally very far from reality. So, the
complexity of the mechanisms involved does not allow to describe the changes in ice
coverage as simple “ice melting”. For comparison: the situation in the Antarctic is even much
more complicated and confusing. The general trend for ice coverage in the whole Antarctic is
close to very stable (no clear overall decrease, but very important year-to-year variations:
Figure 3a).
The western part of the continent - especially the Peninsula and the eastern Amundsen
Sea - however shows a huge decrease, probably the most important one in the world marine
systems, while in other Antarctic areas on the contrary a strong increase is taking place, e.g.
in the Ross and Weddell seas (Figure 3b), looking like a kind of improbable compensation
mechanism and resulting in a stable situation for the Antarctic as a whole. The author actually
observed this phenomenon from RV Polarstern: in March 2010, the eastern Amundsen Sea
(Pine Tree Island Bay) was almost ice-free - an exceptional situation - while satellite images
showed on the contrary an exceptionally high ice coverage in the Ross Sea. Again, such
phenomena cannot be explained by a simple increase of global temperature.
Figure 3. Long term evolution of ice coverage in the Antarctic (% per year for a given
month); a: example of summer (January); b: sea ice concentration trends in summer
(February) (NSIDC).
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Claude R. Joiris
Other mechanisms must be involved, such as an extension of warmer sub-tropical waters
to the South, possibly reaching the most northern part of Antarctica and causing the observed
strong local decrease of pack ice. The disappearance of huge pieces of land fast pack ice from
the eastern Peninsula is well documented and impressive, e.g. the Larsen A and B ice shelf, in
January 1995 and February 2002 respectively (Figure 4).
Ice thinning is also an important phenomenon, generally interpreted as reflecting another
aspect of the decline of Arctic ice coverage. This is however not necessarily the case, and
another explanation is possible, namely that after a year of very poor ice coverage (e.g. 2007),
ice is growing again the year after (Figure 5). This new one-year ice is necessarily thinner
than multi-year pack ice and will become thicker during next years.
Figure 4. Temporal evolution of the extent of the Larsen B shelf till its disappearance in
2002 (NASA, Wikipedia).
Possible Impact of Decreasing Arctic Pack Ice on the Higher Trophic Levels
7
Figure 5. Arctic pack ice extent in August 2007, the year of lowest ice coverage ever
recorded, and August 2008 (top); September 2007 and September 2008 (bottom)
(NSIDC).
This means that thin ice is not necessarily a sign for decreasing ice coverage: after a year
of very poor ice conditions it can, in contrast, reflect a new ice extension.
2. Little auks represent the most abundant seabird species in the Arctic, and probably the
most numerous one on Earth marine ecosystems. They need on the one hand colonies on land,
often huge ones, as breeding site, and depend on the other hand on rich feeding grounds for
bringing back food (polar zooplankton: mainly the Arctic copepods Calanus hyperboreus and
C. glacialis.) to their chicks at the nest. It is often assumed that little auks feed in Polar Water,
while they actually depend on the narrow zone of mixed Polar and Arctic Waters: this usually
8
Claude R. Joiris
takes place at the ice edge, but can also be situated farther from the pack ice, e.g. above
eddies containing this same type of water (Joiris and Falck 2010). The distance between
colony and feeding ground can reach a maximum of 100 to 150 km (Byrkjedal et al. 1974;
Brown 1976; Joiris 1992; Joiris and Tahon 1992). In case of decreasing pack ice, this distance
might become too long, and little auks unable to fly it daily (Figure 6a). In July 2005, adults
were massively leaving the southern Jan Mayen colony by thousands, all flying in exactly the
same direction to the North-North-East: they apparently had to interrupt breeding in order to
reach the ice edge (Figure 6c: arrows)(Joiris 2007; Joiris and Falck 2010). In future years, if a
much stronger decrease in ice coverage similar to the 2005 and 2007 decline was taking
place, the breeding failure might affect the whole Spitzbergen and South-East Greenland
populations (Scoreby Sound with close to half of the world population: more than 10 millions
birds), as well as other seabird species feeding mainly at the ice edge, such as Brünnich’s
guillemot Uria lomvia.
Figure 6. Data collected in the Fram Strait and the Greenland Sea in summer 2005; a
main water masses, fronts, main currents (WSC: West Spitsbergen Current, EGC: East
Greenland Current), pack ice, and ice edge; b numbers of local little auks Alle alle per
half-an-hour count; c numbers of moving little auks per half-an-hour count. Note: the
concentration of local little auks around 0°E, 75°N, marked with a thin line, should not be
taken into account: they were observed in September, i.e. after the end of the breeding
season (Joiris 2007, Joiris and Falck 2010).
Possible Impact of Decreasing Arctic Pack Ice on the Higher Trophic Levels
9
3. Large cetaceans, mainly large baleen whales (Mysticeti), showed a distribution in
separate Arctic populations (stocks) without contacts - or very limited ones only. Such
separations were noted especially between the North Atlantic and the North Pacific oceans, as
well for some species between the north-eastern and the north-western Atlantic. This is the
case for the minke whale Balaenoptera acutorostrata including, as a visible result, the
presence of different patterns between stocks (Steward and Leatherwood 1985). The situation
is less clear for the fin whale B. physalus, with possible limited interactions between stocks
(Gambell 1985). The blue B. musculus and humpback whales Megaptera novaeangliae
showed a separation between North Atlantic and North Pacific populations (Yochem and
Leatherwood 1985, Winn and Reichley 1985). Bowhead Balaena mysticus also showed such
a separation (Reeves and Leatherwood 1985) with very large differences in numbers, the
north-eastern Atlantic (Spitzbergen) stock being at a very low level if not close to extinction:
24 specimens were noted between 1958 and 1982, including one found dead, even if a more
optimistic interpretation mentioned 11 possible sightings off Franz Joseph Land in post-war
years. The north-western Atlantic stock was evaluated as a few hundreds individuals and the
North Pacific one around 8,000 (Klinowska 1991).
Among the large toothed cetaceans (Odontoceti), the sperm whale (Physeter
macrocephalus) was also split in two stocks: the North Atlantic one was estimated as 60,000
adult males and the North Pacific one as 450,000 (Rice 1985)(adult males being the only ones
to migrate into Arctic waters in summer).
This situation implies a physical barrier between both oceans, making exchanges between
stocks highly improbable and very limited, if any. The most logic interpretation is that the
heavy pack ice, including in the North-East and North-West Passages, was bringing on for
such a physical separation between populations of a same species.
Our data about the quantitative distribution of the "higher trophic levels" in the Arctic
since 1979, mainly in the Greenland and Norwegian seas, showed a drastic increase in
numbers of large cetaceans from 2007 on, then the year of lowest ice coverage ever recorded
(Figures 2 and 6). The most striking change concerns the bowhead: one exemplar only was
noted during the periods 1979-1993 and 2003-2005 in 5,600 half-an-hour counts (in June
1988: Joiris and Tahon 1992), but 7 were encountered in 2007 at four counts off West
Spitzbergen, on positions corresponding both to the continental slope and the front between
Polar and Arctic Waters (July 10th, 2007) and 7 in 2008 in 1,174 counts. This same transect
was often visited during previous years, without such whale concentrations: the observed high
numbers are not according to a spatial variation but to a temporal one. The high density was
confirmed during next years, 66 exemplars being encountered in total during 3,630 counts
from 2007 to 2010 (Table 1). Similar high numbers were reported by other observers
(Boertmann et al. 2009, de Korte and Belikov 1994, Gilg and Born 2005, Wiig 1991, Wiig et
al. 2007, 2010) and the increase was mentioned by Gilg and Born (2005), while out of the
total of 46 reported from 1940 to 2009 by Wiig et al. (2010), 35 were actually noted after
2005. This sudden and huge increase obviously cannot be attributed to a growth of the local
population, such a growth seldom reaching 15% per year for large cetaceans (Klinowska
1991) and probably less than 8% per year for the bowhead. The most reasonable interpretation
seems thus to be that the bowheads belonging to different stocks separated by close pack ice,
were able to travel between the North-East and/ or North-West Passages off Alaska, Canada
and/ or Siberia as a consequence of strongly decreasing ice coverage and opening of the
Passages. This caused an inflow from the high Pacific stock to the much lower Atlantic one.
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Claude R. Joiris
Table 1. Summer at-sea distribution of large cetaceans in the Greenland and Norwegian
seas. Mean number per 100 counts (50 hours)
period >
1979 –
1993 a
2003
2005
2007
2008 b
2009
2010
species
number of counts >
3,768
730
1,116
190
1,174
1,328
950
bowhead
Balaena mysticus
< 0.05
0
0
0.4
0.7
1
0
bue whale
Balaenoptera musculus
< 0.05
0
2
0.3
0.3
0.3
1
fin whale
minke
whale
humpback
whale
sperm
whale
Balaenoptera physalus
Balaenoptera
acutorostrata
0.1
2
7
0.6
1.3
5
11
1
1
4
0.5
0.7
0.5
2
Megaptera novaeangliae
< 0.05
0
1
0.2
13
0.3
2
Physeter macrocephalus
0.6
0
1
0.7
0.2
0.6
3
a: 7 expeditions (Joiris 2000); b: (Joiris 2011).
The implication is that the previously separated stocks merged into one single population.
Last but not least, an important consequence is that such a gene flow should in future allow to
avoid the risks of consanguinity, potentially a major problem when population levels are as
low as was the north-eastern Atlantic bowhead stock.
The situation is very similar for the blue, fin and humpback whales (Table 1): 49 blue
whales were encountered in 2007, of which 35 in the selected four counts (see above).
A clear difference, however, is that a first limited increase could already be detected in
2005, with 6 contacts in one week on the slope of the Greenland Plateau (75°N, 00°E), again
corresponding to the front between Polar and Arctic Waters; the same remark might apply to
the fin whale. A possible explanation might be that the large blue and fin whales are able to
travel for longer distances under the ice: the first important decrease of ice coverage in 2005
possibly allowed them to arrive in the north-eastern Atlantic in 2005 already, while the other
large cetaceans such as bowhead could only move from one ocean to the other in 2007 by
much lower ice coverage.
Similar trends can be detected for minke and sperm whales, but these species were
already present in good numbers in the area, so that the increase is less obvious, if any (Table
1).
An open question remains to see if the large whale stocks will stay and reproduce in their
"new" zones, or return to their region of origin for their reproduction cycle as it is often the
case by large, social animals.
4. Polar bear populations are often said as probably declining, if not threatened and
decreasing toward a disappearance on the longer-term, sometimes expressed in decades, due
to decreasing ice coverage. No such trend could, however, be detected yet in our data:
numbers encountered remain stable during the 1988 - 1993 and 2003 - 2010 periods. They
looked healthy (Figures 7a and b), and mothers accompanied by one or two cubs were noted
in usual proportion (Figure 8). The author noticed one exception only, during a helicopter
flight in the Arctic off the coast of Canada in 2009: a bear obviously remained blocked on a
medium sized ice flow, too far from the pack ice, and could not - or did not dare to - swim to
the next floes.
Possible Impact of Decreasing Arctic Pack Ice on the Higher Trophic Levels
11
Figure 7. Polar bear at the end of a meal (carcass of a bearded seal), summer 2008.
Figure 8. Polar bear: mother and cub swimming between two ice floes; summer 2008.
This individual stayed isolated for that long that the floe was entirely covered with its
tracks (Figure 9a), and it was clearly starving (Figure 9b).
12
Claude R. Joiris
Figure 9. Isolated ice floe covered with polar bear tracks and the same bear in movement;
summer 2008.
The actual importance of such a phenomenon can, however, only be overestimated from
observations made from the coast or from local expeditions at the southern limit of the pack
ice, and thus should not be exaggerated: in our data, it concerns by far less than 1% of the
total.
The proposed explanation for the very limited effects - if any - on the bear stocks is that
they are not depending on the entire pack ice as wrongly interpreted, but are mainly
depending on the Outer Marginal Ice Zone (OMIZ), and thus have no heavy problem to
follow it when it is moving north with decreasing pack ice. The same is true for their main
Possible Impact of Decreasing Arctic Pack Ice on the Higher Trophic Levels
13
prey: the pinnipeds (mainly harp seal), in contrast with seabird species depending on breeding
colonies on land and on the ice edge for feeding (e.g. little auk: see above).
CONCLUSION
The long-term evolution of Arctic pack ice shows a decreasing trend, which is obviously
of great importance for both marine and terrestrial ecosystems. This trend is, however, limited
and is to be expressed as 0.25% per year in winter, and 1% per year in summer. Year-to-year
variations can show huge amplitudes, and are thus not to be explained by climatic change
only: indirect consequences influencing the extent of water masses and/ or the main wind
direction and force seem to be the cause of such short-term changes and should be taken into
account separately.
Possible consequences of this phenomenon for marine ecosystems, especially for higher
trophic levels, are firstly to be expected for seabirds, since they depend on land for their
breeding colonies, and some of the most abundant species (little auk) must fly daily to the ice
edge for feeding on polar copepods and bringing back food to their chicks. In years with very
low ice coverage, the distance between colony and ice edge might become too large and the
birds unable to breed successfully: this apparently happened in 2005 for the Jan Mayen
colonies. If on the longer-term the pack ice decease was still taking place, the whole
population and thus the species as such might possibly be threatened, as well as other Arctic
species breeding on Svalbard and Greenland, and showing a similar feeding ecology (e.g.
Brünnich's guillemot).
Secondly, populations of large whales were drastically increasing from 2007 on, a
phenomenon not to be explained by population growth but by an important inflow from the
more numerous Pacific stocks through the recently open North-East and North-West Passages
into the Atlantic area where stocks were close to depletion: an apparently "positive"
consequence for the North Atlantic stocks. Moreover, mixing with other stocks might
improve the genetic heterogeneity of such stocks previously so depleted that inbreeding might
have become a serious problem, if they remain in their new zone instead of going back in
their zone of origin for mating and reproduction.
Thirdly, in contrast with what is often assumed by some scientists and the media, polar
bear populations are not directly influenced by decreasing ice coverage and seem to remain
healthy. They are indeed not depending on the extent of pack ice but on ice edge and OMIZ,
together with their main prey, harp seals: by retreating ice edge, they can - with a few
exceptions - move north and remain in their biotope.
ACKNOWLEDGMENTS
The author is very grateful to the coordinator and the chief scientists for invitation on
board RV Polarstern (AWI, Bremerhaven, Germany) and to the members of the PolE team
having taken part to different expeditions with the author. Jo Dufour made useful comments
allowing to improve a first version of the manuscript.
14
Claude R. Joiris
REFERENCES
Boertmann D, Merkel F, Durinck J (2009) Bowhead whales in East Greenland, summers
2006–2008. Polar Biology 32, 1805–1809.
Brown RGB (1976) The foraging range of breeding dovekies Alle alle. Canadian FieldNaturalist 90,166-168.
Byrkjedal L, Alendal E, Lindberg F (1974) Counts of sea-birds between Norway and
Spitzbergen in the summer 1973. Norsk Polarinst Årbok, 265-269.
de Korte J, Belikov SE (1994) Observations of Greenland whales (Balaena mysticetus),
Zemlya Frantsa-Iosifa. Polar Record 30, 135–136.
Gambel R (1985) Fin whale Balaenoptera physalus (Linnaeus, 1758). In: Ridgway SH and
Harrison RJ (eds): Handbook of marine mammals, vol. 3: The sirenians and baleen
whales. Acad Press, pp 171-192.
Gilg O, and Born EW (2005) Recent sightings of the bowhead whale (Balaena mysticetus) in
Northeast Greenland and the Greenland Sea. Polar Biology 28, 796-801.
Joiris C (1976) Seabirds seen during a return voyage from Belgium to Greenland in July. Le
Gerfaut 66, 63-87.
Joiris CR (1978) Seabirds recorded in the northern North Sea in July: the ecological
implications of their distribution. Le Gerfaut 68, 419-440.
Joiris CR (1992) At-sea distribution and ecological role of seabirds and marine mammals in
the Norwegian and Greenland seas (June 1988). Journal of Marine Systems 3, 73-89.
Joiris CR (2000) Summer at-sea distribution of seabirds and marine mammals in polar
ecosystems: a comparison between the European Arctic seas and the Weddell Sea,
Antarctica. Journal of Marine Systems 27, 267-276.
Joiris CR (2007) At-sea distribution of seabirds and marine mammals in the Greenland and
Norwegian seas: impact of extremely low ice coverage. Symposium “European Research
on
Polar
Environment
and
Climate”,
Brussels,
5-6
March
2007
http://ec.europa.eu/research/environment/newsanddoc/agenda0307_en.htm
Joiris CR (2011) A major feeding ground for cetaceans and seabirds in the south-western
Greenland Sea. Polar Biology doi:10.1007/s00300-011-1022-1. In press.
Joiris CR, Falck E (2010) Summer at-sea distribution of little auks Alle alle and harp seals
Pagophilus (Phoca) groenlandica in the Greenland Sea: impact of small-scale
hydrological events. doi:10.1007/s00300-010-0910-0, 3 November 2010. Polar Biology
34, 541-548 (2011).
Joiris CR, Kampp K, Tahon J, Møbjerg Kristensen R (1997) Summer distribution of seabirds
in the North-East Water polynya, Greenland. Journal of Marine Systems 13, 51-59.
Joiris CR, Tahon J (1992) Distribution and food intake of seabirds and marine mammals in
the Norwegian and Greenland seas (July 1988). Royal Academy of Overseas Sciences,
Brussels, pp 113-133.
Joiris CR, Tahon J, Holsbeek L, Vancauwenberghe M (1996) Seabirds and marine mammals
in the eastern Barents Sea: late summer at-sea distribution and calculated food intake.
Polar Biology 16, 245-256.
Klinowska M Dolphins, porpoises and whales of the world, the IUCN red data book, IUCN,
Gland, Switserland and Cambridge, U.K; 1991.
Possible Impact of Decreasing Arctic Pack Ice on the Higher Trophic Levels
15
Pocklington R (1979) An oceanographic interpretation of seabird distributions in the Indian
Ocean. Marine Biology 51, 9-21.
Reeves RR and Leatherwood S (1985) Bowhead whale Balaena mysticetus Linnaeus, 1758.
In: Ridgway SH and Harrison RJ (eds): Handbook of marine mammals, vol. 3: The
sirenians and baleen whales. Acad Press, pp 305-344.
Rice DW (1985) Sperm whale Physeter macrocephalus Linnaeus, 1758. In: Ridgway SH and
Harrison RJ (eds): Handbook of marine mammals, vol. 3: The sirenians and baleen
whales. Acad Press, pp 177-234.
Steward SB and Leatherwood S (1985) Minke whale Balaenoptera acutorostrata Lacépède,
1804. In: Ridgway SH and Harrison RJ (eds): Handbook of marine mammals, vol. 3: The
sirenians and baleen whales. Acad Press, pp 91-136.
Wiig Ø (1991) Seven bowhead whales (Balaena mysticetus L.) observed at Franz Josef Land
in 1990. Marine Mammals Science 7, 316-319.
Wiig Ø, Bachmann L, Janik VM, Kovacs KM and Lydersen C (2007) Spitzbergen bowhead
whales revisited. Marine Mammals Science 23, 688-693.
Wiig Ø, Bachmann L, Øien N, Kovacs KM and Lydersen C (2010) Observations of bowhead
whales (Balaena mysticetus) in the Svalbard area 1940-2009. Polar Biology 33, 979-984.
Winn HE and Reichley NE (1985) Humpback whale Megaptera novaeangliae (Borowski,
1781). In: Ridgway SH and Harrison RJ (eds): Handbook of marine mammals, vol. 3:
The sirenians and baleen whales. Acad Press, pp 241-273
Yochem PK and Leatherwood S (1985) Blue whale Balaenoptera musculus (Linnaeus, 1758).
In: Ridgway SH and Harrison RJ (eds): Handbook of marine mammals, vol. 3: The
sirenians and baleen whales. Acad Press, pp 193-240
Reviewed by
Dr Eva Falck, University of Bergen, Norway.