Changes in Greenland’s peripheral glaciers linked to the North Atlantic Oscillation

Glaciers and ice caps peripheral to the main Greenland Ice Sheet contribute markedly to sea-level rise1,2,3. Their changes and variability, however, have been difficult to quantify on multi-decadal timescales due to an absence of long-term data4. Here, using historical aerial surveys, expedition photographs, spy satellite imagery and new remote-sensing products, we map glacier length fluctuations of approximately 350 peripheral glaciers and ice caps in East and West Greenland since 1890. Peripheral glaciers are found to have recently undergone a widespread and significant retreat at rates of 12.2 m per year and 16.6 m per year in East and West Greenland, respectively; these changes are exceeded in severity only by the early twentieth century post-Little-Ice-Age retreat. Regional changes in ice volume, as reflected by glacier length, are further shown to be related to changes in precipitation associated with the North Atlantic Oscillation (NAO), with a distinct east–west asymmetry; positive phases of the NAO increase accumulation, and thereby glacier growth, in the eastern periphery, whereas opposite effects are observed in the western periphery. Thus, with projected trends towards positive NAO in the future5,6, eastern peripheral glaciers may remain relatively stable, while western peripheral glaciers will continue to diminish

Surface velocity of the Northeast Greenland Ice Stream (NEGIS): assessment of interior velocities derived from satellite data by GPS

The Northeast Greenland Ice Stream (NEGIS) extends around 600 km upstream from the coast to its onset near the ice divide in interior Greenland. Several maps of surface velocity and topography of interior Greenland exist, but their accuracy is not well constrained by in situ observations. Here we present the results from a GPS mapping of surface velocity in an area located approximately 150 km from the ice divide near the East Greenland Ice-core Project (EastGRIP) deep-drilling site. A GPS strain net consisting of 63 poles was established and observed over the years 2015–2019. The strain net covers an area of 35 km by 40 km, including both shear margins. The ice flows with a uniform surface speed of approximately 55 m a^−1 within a central flow band with longitudinal and transverse strain rates on the order of 10−4 a^−1 and increasing by an order of magnitude in the shear margins. We compare the GPS results to the Arctic Digital Elevation Model and a list of satellite-derived surface velocity products in order to evaluate these products. For each velocity product, we determine the bias in and precision of the velocity compared to the GPS observations, as well as the smoothing of the velocity products needed to obtain optimal precision. The best products have a bias and a precision of ∼0.5 m a^−1. We combine the GPS results with satellite-derived products and show that organized patterns in flow and topography emerge in NEGIS when the surface velocity exceeds approximately 55 m a−1 and are related to bedrock topography

Utilization and transfer of forest genetic resources: A global review

AbstractOver the last 200years, genetic resources of forest trees have been increasingly transferred, within and outside of species’ native distribution ranges, for forestry and for research and development (R&D). Transferred germplasm has been deployed to grow trees for numerous purposes, ranging from the production of wood and non-wood products to the provision of ecosystem services such as the restoration of forests for biodiversity conservation. The oldest form of R&D, provenance trials, revealed early on that seed origin has a major influence on the performance of planted trees. International provenance trials have been essential for selecting seed sources for reforestation and for improving tree germplasm through breeding. Many tree breeding programmes were initiated in the 1950s, but as one round of testing and selection typically takes decades, the most advanced of them are only in their third cycle. Recent advances in forest genomics have increased the understanding of the genetic basis of different traits, but it is unlikely that molecular marker-assisted approaches will quickly replace traditional tree breeding methods. Furthermore, provenance trials and progeny tests are still needed to complement new research approaches. Currently, seed of boreal and temperate trees for reforestation purposes are largely obtained from improved sources. The situation is similar for fast growing tropical and subtropical trees grown in plantations, but in the case of tropical hardwoods and many agroforestry trees, only limited tested or improved seed sources are available. Transfers of tree germplasm involve some risks of spreading pests and diseases, of introducing invasive tree species and of polluting the genetic make-up of already present tree populations. Many of these risks have been underestimated in the past, but they are now better understood and managed. Relatively few tree species used for forestry have become invasive, and the risk of spreading pests and diseases while transferring seed is considerably lower than when moving live plants. The implementation of the Nagoya Protocol on access to genetic resources and benefit sharing (ABS) may significantly change current transfer practices in the forestry sector by increasing transaction costs and the time needed to lawfully obtain forest genetic resources for R&D purposes. Many countries are likely to struggle to establish a well-functioning ABS regulatory system, slowing down the process of obtaining the necessary documentation for exchange. This is unfortunate, as climate change, outbreaks of pests and diseases, and continual pressure to support productivity, increase the need for transferring tree germplasm and accelerating R&D