Posts by Yuanrong Zhou

Where Can Alpine Plants Hide from Global Warming?

Posted by on Mar 17, 2015 in Adaptation, All Posts, Featured Posts, Science | 0 comments

Where Can Alpine Plants Hide from Global Warming?

Spread the News:ShareEnvironmental conditions, including climate, strongly influence the distribution of plant species. As temperatures continue to rise around the world, many people are concerned about the possible shifts in distribution of plant species, since plants are immobile, and many of them have a limited ability to disperse. These restrictions to changes in their distribution are particularly severe for plants that are adapted to cold conditions, such as those found in high mountain regions. Studies by Valenti Rull and others have shown that during interglacial periods in the geological past, alpine plants were able to disperse to microrefugia, small-scale sites which allowed species to persist when most of their ranges became unsuitable for them. Thus, in the current era of warming, such sites, with locally favorable climate, could once again prove to be important for the survival of cold-adapted alpine species. A newly published study by Rodolfo Gentili of the Department of Environmental Sciences at the University of Milan and several co-authors in Ecological Complexity establishes a fresh approach to the study  of microrefugia. The authors examined the geomorphological and ecological features of microrefugia during earlier interglacial stages and used these features to identify potential microrefugia areas for alpine plants in and near glaciers, in both the present and the near future. In general, there are three recognized strategies which alpine plants can adapt to survive under a warming climate. They can migrate to higher elevation, remain at local microrefugia or evolve through genetic differentiation to adapt to new climate. However, there had been no overview to date of how plants in the Alps and other high mountains of Europe could respond to future warming. Gentili and his co-authors conducted  a thorough literature review, focusing in particular on geomorphological processes and landforms associated with plant communities in alpine environment. (They found only one study which addressed the genetic evolution of an alpine plant.) The authors developed a typology of alpine landforms and characterized each one according to its “vegetation features, climatic controls, microclimate features of active landforms and microrefugium functions.” They recognized eight landform types, which differ in terms of the processes that generate them. These landforms are mountain summits, debris-covered glaciers, moraine ridges and deglaciated forelands, nivation niches or snow patches,rock glaciers, alpine composite debris cones (debris slopes and scree), alpine corridors (composite channels, including avalanche channels and tracks), and ice caves. Taken individually, all of these eight landforms have been documented in the published literature as serving currently as microrefugia, except for the debris-covered glaciers, which nonetheless are promising as future microrefugia because of their relatively cool temperatures which result from the presence of sub-surface ice. The other landforms all have been shown to function as microrefugia. They offer a number of advantages, including suitable sites for colonization (moraine ridges and deglaciated forelands), cooler temperatures (debris-covered glaciers, rock glaciers, nivation niches or snow patches, ice caves), a vertical range that facilitates dispersal (alpine corridors) and a large variety of niches (alpine composite debris cones). Taken together, these landforms provide a very wide range of habitats, increasing the likelihood that any given alpine species could have a favorable spot to which it could disperse. These relations are indicated in the figure from the paper, shown below, which demonstrates that the geomorphological heterogeneity—the diversity of habitats within and across landforms—promotes the survival of species. The researchers note that these glacial and pre-glacial landforms are potential microrefugia for alpine plants under warming conditions. They recognize that human intervention—purposive translocation of plants—may assist in the survival of species. In addition, they point out that the plant species themselves may adapt genetically to changing environmental conditions. They conclude by suggesting that...

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Glaciers Influence Marine Invertebrates in Chile

Posted by on Feb 25, 2015 in All Posts, Featured Posts, Science, Uncategorized | 0 comments

Glaciers Influence Marine Invertebrates in Chile

Spread the News:ShareZooplankton are tiny creatures that drift in water bodies. A recent study by Meerhoff et al. in Progress in Oceanography describes linkages which connect them with glaciers. The researchers observed meroplankton—organisms which have planktonic features in their larval stages, but live sessile in the bottom as adults. They worked in the fjords of the Baker River, which is located between the Northern and Southern Patagonian ice fields in Chile. Physical and chemical conditions vary widely in these fjords, due to tides and to seasonal fluctuations in glacier meltwater and other contributions to river flow. These varying conditions, in turn, influence the dynamics of zooplankton communities, including productivity patterns, biomass, and community structure (the distribution and interactions of different species). Zooplankton community dynamics in fjords are influenced by the strong vertical and horizontal gradients in hydrographic structure, such as freshwater discharge and tides. Studies have shown that temporal and spatial distributions of zooplankton are controlled by environmental conditions. Temperatures influence temporal scale by influencing metabolic rates and swimming behaviors of zooplankton. The salinity of water constrains the spatial distribution of estuarine zooplankton because each species can tolerate only certain levels of salinity. These two environmental factors also influence food availability and predation stress, which also affects the community structure of zooplankton. The input of freshwater from glacial meltwater can change salinity, generate internal tides and reshape the circulation pattern in estuarine systems. Moreover, the turbidity of the water is influenced by glacial input. Even though the glaciers are virtually pristine, the meltwater is able to carry sediments along its way, known as rock flour. These finely ground particles, formed by the interaction of glaciers with their beds, are so small that they remain in suspension, making the water less transparent. This increase in turbidity limits light penetration and thus restricts primary production through photosynthesis by phytoplankton—the minute plants which float in the water column. Using vertical tows, Meerhoff and her associates collected samples in three sites close to the river mouth, during the Baker river minimum outflow season (October 2012) and during the maximum outflow season (February 2013). They observed strong hydrographic gradients, both horizontal and vertical, in early spring (October) and late summer (February). They have also found that these two seasons are significantly distinct in water-column conditions. Such variations are largely caused by freshwater discharges from nearby glaciers. This study found a number of kinds of meroplankton in these fjords; the dominant organisms are larval forms of barnacles, squat lobsters, crabs, snails and bivalves. The study also indicated that zooplankton community shows seasonal variations. Specifically, barnacle larvae are favored in spring, when river outflow is at its minimum, while its food sources, phytoplankton, are more abundant. In contrast, bivalve larvae are dominant in summer due to higher surface water temperature. At this time, river outflow is at its maximum and phytoplankton availability is much lower than in spring, reflecting the greater turbidity of the water that carries glacier rock flour. Studies are needed to demonstrate whether bivalve larvae in this estuary feed on bacteria when phytoplankton are unavailable, as they do in other regions. This study shows how freshwater input, along with other factors, affects zooplankton composition and distribution. It is remarkable to think of the numerous marine invertebrate larvae whose populations respond to glaciers located well inland of their estuarine home. Look here for other stories about invertebrate life near and on glaciers. Spread the...

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Photo Friday: Volcanoes in Ecuador

Posted by on Feb 13, 2015 in All Posts, Art/Culture, Featured Posts, Images | 0 comments

Photo Friday: Volcanoes in Ecuador

Spread the News:ShareEcuador has a series of beautiful cone-shaped volcanoes along the Andes. This week, GlacierHub features three volcanoes from Ecuador: Cayambe, Chimborazo, and Tungurahua. Cayambe, locating in the Cordillera Central, is a Holocene compound volcano. Chimborazo, locating in the Cordillera Occidental, is the highest mountain in Ecuador. These two volcanoes are currently inactive. On the other hand, Tungurahua is an active volcano, located in the Cordillera Oriental. Photo Friday highlights photo essays and collections from areas with glaciers. If you have photos you’d like to share, let us know in the comments, by Twitter @glacierhub or email us at glacierhub@gmail.com. Tungurahua_desde_patate Chimborazo2004 Chimborazo Cayambe2 Chimborazo2 Tungurahua Cayambe Spread the...

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Photo Friday: Yerupaja

Posted by on Feb 6, 2015 in All Posts, Art/Culture, Featured Posts, Images | 0 comments

Photo Friday: Yerupaja

Spread the News:ShareThe mountain Yerupaja in the Cordillera Huayhuash locates at the west central Peru. It is part of the Peruvian Andes and ranks as the second highest mountain in Peru. As one of the hardest mountains along the Andes to climb, it draws mountaineers from all over the world, who come to conquer this high peak. For more photos featuring glaciers from Peru, look here. Photo Friday highlights photo essays and collections from areas with glaciers. If you have photos you’d like to share, let us know in the comments, by Twitter @glacierhub or email us at glacierhub@gmail.com. 4416897719_73809f0a5d_z 16233269358_f231b88f8d_c 16235001187_43e019435f_c 3720052781_bdb4bd1a3c_z 16419997642_60134ac874_c 15800849623_2e11205150_h Spread the...

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Melting Glaciers Give Earth a Pop

Posted by on Feb 3, 2015 in All Posts, Featured Posts, News, Science | 0 comments

Melting Glaciers Give Earth a Pop

Spread the News:ShareThough the Earth often seems solid and fixed, it is not. You’ve probably heard of continental drift—the horizontal movement of continent-sized bodies of rock—but fewer of you may appreciate that the earth can move vertically as well. Studies have shown that North America and Europe are rebounding, slowly but steadily, due to the removal of thick ice sheets which once covered them during the last ice age, which ended about 21,000 years ago. This process of postglacial upward movement is called glacial isostatic adjustment (GIA). Researchers have established that some materials have a viscous response when a surface load is placed on them, flowing like slow-moving honey, and remaining deformed when the load is removed; others have an elastic response, stretching like rubber and bouncing back to their original form. The substances that compose the upper sections of the earth are somewhere between these extremes, and have what is termed a viscoelastic response. As a result, when a mass of an icesheet is removed, the solid Earth underneath may display some degree of rebound. It was observed that the uplift rate in North America and Europe can reach 1 cm/yr. Researchers have established that the formation of icesheets generated pressure on the underlying rocks, pushing them downward. In addition to this downward dislocation of the crust, the mantle beneath might be compressed as well. Previous studies on GIA have seldom included this compressibility of the Earth in their calculations, because of the complexities and uncertainties that it would introduce into quantitative models. But a paper published by Tanaka et al. earlier this year in the Journal of Geodynamics established a model which includes compressibility for the GIA in southeast Alaska and compared this model to another which did not include compressibility. Southeast Alaska, which is also referred to as the Alaska Panhandle, lies west of the Canadian province of British Columbia. This region is known to have the largest GIA rate in North America, approximately 30 mm/yr. The reseachers anticipated that the compressibility effects would be larger and easier to detect in this region. In this region, models of GIA integrate the effect of ice sheet mass variations over three periods: the Last Glacial Maximum (LGM) about 20,000 years ago, the Little Ice Age a few centuries ago (LIA) and present-day (PD). Measurements of rebound at different locations can serve to test these models, since information is available on the extent of icesheets in different periods. It is known, for example, that icesheets retreated earlier at lower elevations, so effects from earlier periods will be stronger there. In the case of southeast Alaska, rebound results primarily from post-LIA and PD ice melting; the former, larger in magnitude, was incorporated into the compressibility model. This model examined the rheological properties of the Earth’s mantle—the geological processes which allow rocks to flow on long time scales, and a second set of properties, called flexural rigidity, which determine the capacity of the earth’s crust to bend. The authors conclude that their modeling efforts demonstrate the value of including compressibility. Without this element, the current uplift rate in southeast Alaska would be 27% (4 mm/yr) slower, and as a result would not match field measurements as well. Phrased in simpler language, they show that the vast ice sheets of the past not only pushed the mantle down, but squeezed it as well. This study demonstrates the great power of ice to alter our planet’s surface, and indicates that it can have measurable effects centuries, or millennia, after it melts. Spread the...

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