Climate and vegetation interactions in the Arctic

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Papaver radicatum (arctic poppy), a flowering plant of the Arctic tundra follows the sun around the sky during the 24-hour daylight of summer north of the Arctic Circle.

Changing climate conditions are amplified in polar regions and northern high-latitude areas are projected to warm at twice the rate of the global average.[1] These modifications result in ecosystem interactions and feedbacks that can augment or mitigate climatic changes. These interactions may have been important through the large climate fluctuations since the glacial period (the last ca. 14,500 years). Therefore it is useful to review the past dynamics of vegetation and climate to place recent observed changes in the Arctic into context. This article focuses on northern Alaska where there has been much research on this theme.

Recent changes

As the

climate feedbacks, improving Earth System Models, and projecting future changes in tundra ecosystems.[8]

Tundra fire scar, July 2015: Mingvk Lake Fire, Quartz Creek, Seward Peninsula, AK. Photo was taken less than one month after fire.
Climate-vegetation interactions associated with shrub expansion in Arctic tundra ecosystems
Positive feedbacks [6][12][13][14][15][9] Negative feedbacks [6][16] Landscape changes [16]

Past
climate change

Shifting vegetation assemblages and fire regimes in the Arctic are of current research priority because of the strength of feedbacks with the global climate system, however, instrumental and historical observations are of limited duration and extent. Consequently, our ability to infer the potential magnitude and direction of change that this region may experience as a result of future climatic changes is hindered. However, a close analysis of Late Quaternary dynamics throughout this region can enhance our understanding of biotic responses to shifts in climate by providing insight as to how past ecosystems in this area were modified by a variety of environmental conditions.[17] Since the climate of the historical record has only demonstrated a fraction of the natural variability seen throughout earth's history (or even that of the Quaternary period), this work will augment contemporary research into the dynamics of climate-induced vegetation change.[17][6]

Quaternary
climate change
in arctic Alaska

Pleistocene (2.58 ma – 11.7 ka)

The

epoch
.

Holocene (11.7 – 4.2 ka)

Throughout the early

insolation levels began to decrease.[22][21] The timing of the middle Holocene thermal maximum was significantly later than originally inferred (it had previously been suggested that this warm period began during the early Holocene 11.0-9. Ka), however multiproxy analysis has demonstrated that there was not a uniform thermal maximum throughout northwestern Alaska at that point.[24][23]

Past ecosystem change

Quaternary environmental change in Arctic Alaska

Pleistocene

Tundra ecosystems developed in the Northern Hemisphere toward the end of the Pliocene (3.6 ma), prior to this point the Arctic was predominantly covered with forests and shrublands which extended northward to the coastline of the Arctic Ocean. However, during the middle Pleistocene this vegetation pattern shifted to a graminoid tundra steppe.[18] This transition away from taller-statured vegetation continued further until reaching an extreme during the Last Glacial Maximum, when forests did not reach north of 55°N except for areas where cryptic refugia occurred within Beringia.[21][25] Likely due to the aridity (and resultant lack of snow cover) throughout the unglaciated region at this time shrub tundra was highly limited in extent in comparison to prior ecosystems. Instead, across Beringia graminoid tundra steppe formed a mosaic with prostrate dwarf shrub, and graminoid forb tundra (an ecotype that is currently restricted today).[18][21] Representative of the large magnitude climatic changes occurring throughout this time, the vegetation patterns of the Pleistocene demonstrate large expansions and contractions of various ecosystems.

Holocene

During the dramatic landscape transition occurring throughout Beringia from the Pleistocene LGM into the early Holocene the arid tundra was replaced as shrubs expanded in warmer and wetter periods, eventually creating the mosaic of

Holocene thermal maximum the landscape continued to transform as peatland and thaw lakes formed at high rate. However, these changes reached a peak between 11 and 10 ka prior to decreasing throughout the early Holocene as changing seasonality rather than temperature alone modified landscape processes and vegetation shifts.[23] Shifting range limits and plant assemblages were further impacted by soil type, as a result vegetation change was not controlled by climatic conditions alone.[28][18]

Spatiotemporal variability

During the dramatic transformations that occurred globally throughout the late Pleistocene, the area of Beringia experienced relatively minor

climatic change.[17]

See also

Climate change in the Arctic

References

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  19. ^ "Bering Land Bridge Animation". instaar.colorado.edu. Retrieved 2018-12-03.
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