Decline of vegetation seasonality is increasing greening in the Arctic
A new NASA-funded study "Temperature and vegetation seasonality diminishment over northern lands" published in Nature Climate Change reports that decreasing temperature difference between the seasons in the North is increasing plant growth and blurring the distinction between the normally more-seasonal North and abutting less-seasonal South. Research Professor Bruce Forbes from the Arctic Centre, University of Lapland was one member of the international team of researchers participating in the study.
Satellite measurements of
vegetation greenness and thermometer data show strong linear
relationships between temperature seasonality and vegetation seasonality
over the past 30 years in the Arctic and Boreal terrestrial biomes.
Temperature seasonality of the area has diminished during the studied
period by an amount equivalent to a 4–5 degree southward shift in
latitude. The estimates from the climate models are that by the end of
the 21st century the additional diminishment could result in an 18
degrees southward shift in latitude.
Diminishment of northern
vegetation seasonality means increase in plant growth. “Indigenous
Nenets reindeer nomads in northern Russia are already experiencing this
through in situ increases in deciduous shrub height and biomass, which
affects herd management, even though the coniferous tree line has yet to
migrate north appreciably in their region”, said Prof. Bruce Forbes,
coauthor from the Arctic Centre, University of Lapland in Rovaniemi,
“The northward migration of the boreal to the Arctic is
apparently slower than anticipated only a few years ago, but the tundra
is already changing from within,” he added. Any significant alterations
to temperature and vegetation seasonality are likely to impact life not
only in the North but elsewhere through atmospheric feedbacks driven by
ongoing changes in tundra albedo and snow capture, he concluded.
international team of 21 researchers from 17 institutions in 7
countries used a new 30-year satellite data set of vegetation greenness.
To determine the growing season, the authors used 20 years of
twice-daily satellite observations of freeze/thaw state of the ground
developed under NASA’s auspices. The authors cast seasonality changes
using latitude as a yardstick because total growing season warmth and
plant growth of circumpolar belts of land monotonically decrease pole
ward from about 50⁰N latitude. This allowed definition of reference
latitudinal profiles of these quantities and translation of their
changes over time as shifts along these reference profiles.
The study was led by Professor Ranga Myneni in cooperation with a doctoral student Liang Xu, from Boston University, USA.
Graphics and more information about the study
The paper can obtained once it is published here (search with DOI number: 10.1038/NCLIMATE1836).
Nature Climate Change
Research Professor Bruce Forbes
Tel. +358 40 847 9202
bruce.forbes (at) ulapland.fi
Professor Ranga Myneni
Tel +1 617 470 7065
ranga.myneni (at) gmail.com
ULapland / Arctic Centre / JL