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Geographic variation and temporal trends in ice phenology in Norwegian lakes during the period 1890–2020
Ist Teil von
The cryosphere, 2021-05, Vol.15 (5), p.2333-2356
Ort / Verlag
Katlenburg-Lindau: Copernicus GmbH
Erscheinungsjahr
2021
Link zum Volltext
Quelle
EZB Electronic Journals Library
Beschreibungen/Notizen
Long-term observations of ice phenology in lakes are ideal for studying
climatic variation in time and space. We used a large set of observations
from 1890 to 2020 of the timing of freeze-up and break-up, and the length of
ice-free season, for 101 Norwegian lakes to elucidate variation in ice
phenology across time and space. The dataset of Norwegian lakes is unusual,
covering considerable variation in elevation (4–1401 m a.s.l.) and
climate (from oceanic to continental) within a substantial latitudinal and
longitudinal gradient (58.2–69.9∘ N, 4.9–30.2∘ E). The average date of ice break-up occurred later in spring with increasing
elevation, latitude and longitude. The average date of freeze-up and the
length of the ice-free period decreased significantly with elevation and
longitude. No correlation with distance from the ocean was detected,
although the geographical gradients were related to regional climate due to
adiabatic processes (elevation), radiation (latitude) and the degree of
continentality (longitude). There was a significant lake surface area effect
as small lakes froze up earlier due to less volume. There was also a
significant trend that lakes were completely frozen over later in the autumn
in recent years. After accounting for the effect of long-term trends in the
large-scale North Atlantic Oscillation (NAO) index, a significant but weak trend over time for earlier
ice break-up was detected. An analysis of different time periods revealed significant and accelerating
trends for earlier break-up, later freeze-up and completely frozen lakes
after 1991. Moreover, the trend for a longer ice-free period also
accelerated during this period, although not significantly. An understanding of the relationship between ice phenology and geographical
parameters is a prerequisite for predicting the potential future
consequences of climate change on ice phenology. Changes in ice phenology
will have consequences for the behaviour and life cycle dynamics of the
aquatic biota.