Retinal oxygen metabolism in patients with mild cognitive impairment

Publisher's version (útgefin grein)Introduction We have previously reported that retinal vessel oxygen saturation is increased in mild-to-moderate dementia of Alzheimer's type when compared with healthy individuals. Mild cognitive impairment (MCI) is the predementia stage of the disease. The main purpose was to investigate if these changes are seen in MCI. Methods Retinal vessel oxygen saturation was measured in 42 patients with MCI and 42 healthy individuals with a noninvasive retinal oximeter, Oxymap T1. The groups were paired according to age. Results Arteriolar and venular oxygen saturation was increased in MCI patients compared to healthy individuals (arterioles: 93.1 ± 3.7% vs. 91.1 ± 3.4%, P = .01; venules: 59.6 ± 6.1% vs. 54.9 ± 6.4%, P = .001). Arteriovenous difference was decreased in MCI compared to healthy individuals (33.5 ± 4.5% vs. 36.2 ± 5.2%, P = .01). Discussion Increased retinal vessel oxygen saturation and decreased arteriovenous difference in MCI could reflect less oxygen extraction by retinal tissue. This indicates that retinal oxygen metabolism may be affected in patients with MCI.Olof Birna Olafsdottir received a grant from the Icelandic Centre for Research. The sponsor did not have any role in the study design; in the collection, analysis, and interpretation of the data; in the writing of the report, and in the decision to submit the article for publication.Peer Reviewe

Retinal oxygen metabolism in patients with mild cognitive impairment

Publisher's version (útgefin grein)Introduction We have previously reported that retinal vessel oxygen saturation is increased in mild-to-moderate dementia of Alzheimer's type when compared with healthy individuals. Mild cognitive impairment (MCI) is the predementia stage of the disease. The main purpose was to investigate if these changes are seen in MCI. Methods Retinal vessel oxygen saturation was measured in 42 patients with MCI and 42 healthy individuals with a noninvasive retinal oximeter, Oxymap T1. The groups were paired according to age. Results Arteriolar and venular oxygen saturation was increased in MCI patients compared to healthy individuals (arterioles: 93.1 ± 3.7% vs. 91.1 ± 3.4%, P = .01; venules: 59.6 ± 6.1% vs. 54.9 ± 6.4%, P = .001). Arteriovenous difference was decreased in MCI compared to healthy individuals (33.5 ± 4.5% vs. 36.2 ± 5.2%, P = .01). Discussion Increased retinal vessel oxygen saturation and decreased arteriovenous difference in MCI could reflect less oxygen extraction by retinal tissue. This indicates that retinal oxygen metabolism may be affected in patients with MCI.Olof Birna Olafsdottir received a grant from the Icelandic Centre for Research. The sponsor did not have any role in the study design; in the collection, analysis, and interpretation of the data; in the writing of the report, and in the decision to submit the article for publication.Peer Reviewe

Breytingar á suðaustanverðum Vatnajökli, fortíð, nútíð og framtíð

The temperate outlet glaciers of SE-Vatnajökull are sensitive to climate change, and provide important climatic and glaciologic information through their recorded variations in mass balance and extent. They descend to the coast from an elevation of 1500–2100 m a.s.l., are located in one of the warmest and wettest area in Iceland and have among the highest mass turnover rates worldwide. The area was settled in the 9th century, and people have lived in close proximity to the glaciers, which has led to numerous contemporary written documents, also provided by the travelers and explorers of the 18th and 19th centuries. According to the unique local historical records, the outlet glaciers advanced in the latter half of the 17th century and extended far out on the lowlands in the mid-18th century. The glaciers were at their LIA terminal moraines around 1880–1890 and soon thereafter started retreating. The well-preserved glacial geomorphological features (including lateral moraines, trimlines and erratics) outlining the LIA maximum extent of the glaciers, have been mapped in this study. A reconstruction of the LIA glacier surface geometry was made, based on the geomorphological data, historical photographs, and information from the oldest reliable topographic maps of 1904. A LiDAR (laser scanning) digital elevation model (DEM) from 2010/2011 provided a reference topography for the reconstruction. From the elevation of the uppermost LIA lateral moraines, the equilibrium line altitude (ELA) was estimated to have been ~300 m lower during the LIA than around 2010. Various datasets on glacier extent and geometry since the end of the 19th century have been used to derive area and volume changes for the period 1890–2010. DEMs have been created from maps, aerial images, DGPS measurements and airborne surveys. In the period 1890–2010 the glacierized area shrunk by 164 km2, the outlet glaciers lowered by 150–270 m near the terminus and collectively lost 60±8 km3 of ice, equal to a global mean sea level rise of 0.15±0.02 mm. The bedrock topography of SE-Vatnajökull has previously been surveyed with radio echo sounding (RES) measurements, allowing relative volume change estimates, indicating that they have lost 15–50% of their LIA maximum volume. The geodetic mass balance has been estimated by subtracting the DEMs from each other. The most negative balance was observed between 2002 and 2010, when the glaciers lost on average –1.34±0.12 m w.e. a-1, which is among the highest rates of mass loss worldwide in the early 21st century. The variable dynamic response of the glaciers to similar climate forcing is related to their different hypsometry, bedrock topography, and the presence of proglacial lakes. The time series of area and volume changes of the entire post-LIA period created in this thesis provided an opportunity to evaluate the empirical volume-area scaling relation, indicating that ice volume may be underestimated by 50% if applying the commonly proposed constants of the power law. A vertically integrated Shallow Ice Approximation ice-flow model, coupled with a positive degree–day surface mass balance model, is used to simulate the evolution of the three outlet glaciers descending from the dome of Breiðabunga, constrained with the observed history of volume change. The degree–day model uses downscaled daily precipitation derived from an orographic precipitation model, that simulates well the observed pattern of winter mass balance variance. Simulations imply that the LIA maximum ice volume is reached with 1°C lower temperatures than the average of the 1980–2000 baseline period and a 20% decrease in annual precipitation, which is in line with meteorological data from nearby lowland stations. Applying a step change in temperature of +3°C, as predicted by some future scenarios will be reached by 2100, the model simulations indicate that the glaciers would loose 80–90% of their present volume.Rannsóknasjóður Háskóla Íslands Vegagerðin Kvískerjasjóður SVALI (Nordic Centre of Excellence

Microplastics in Glaciers: First Results from the Vatnajökull Ice Cap

Microplastic particles, as a second-phase material in ice, may contribute to the effect such particles have on the melting and rheological behaviour of glaciers, and thus influence the future meltwater contribution to the oceans and rising sea levels. Hence, it is of the utmost importance to map and understand the presence and dispersal of microplastics on a global scale. In this work, we identified microplastic particles in snow cores collected in a remote and pristine location on the Vatnajökull ice cap in Iceland. Utilising optical microscopy and µ-Raman spectroscopy, we visualised and identified microplastic particles of various sizes and materials. Our findings support that atmospheric transport of microplastic particles is one of the important pathways for microplastic pollution

Glacier changes in Iceland from 1890 to 2019

The volume of glaciers in Iceland (∼3,400 km3 in 2019) corresponds to about 9 mm of potential global sea level rise. In this study, observations from 98.7% of glacier covered areas in Iceland (in 2019) are used to construct a record of mass change of Icelandic glaciers since the end of the 19th century i.e. the end of the Little Ice Age (LIA) in Iceland. Glaciological (in situ) mass-balance measurements have been conducted on Vatnajökull, Langjökull, and Hofsjökull since the glaciological years 1991/92, 1996/97, and 1987/88, respectively. Geodetic mass balance for multiple glaciers and many periods has been estimated from reconstructed surface maps, published maps, aerial photographs, declassified spy satellite images, modern satellite stereo imagery, and airborne lidar. To estimate the maximum glacier volume at the end of the LIA, a volume–area scaling method is used based on the observed area and volume from the three largest ice caps (over 90% of total ice mass) at 5–7 different times each, in total 19 points. The combined record shows a total mass change of −540 ± 130 Gt (−4.2 ± 1.0 Gt a−1 on average) during the study period (1890/91 to 2018/19). This mass loss corresponds to 1.50 ± 0.36 mm sea level equivalent or 16 ± 4% of mass stored in Icelandic glaciers around 1890. Almost half of the total mass change occurred in 1994/95 to 2018/19, or −240 ± 20 Gt (−9.6 ± 0.8 Gt a−1 on average), with most rapid loss in 1994/95 to 2009/10 (mass change rate −11.6 ± 0.8 Gt a−1). During the relatively warm period 1930/31–1949/50, mass loss rates were probably close to those observed since 1994, and in the colder period 1980/81–1993/94, the glaciers gained mass at a rate of 1.5 ± 1.0 Gt a−1. For other periods of this study, the glaciers were either close to equilibrium or experienced mild loss rates. For the periods of AR6 IPCC, the mass change rates are −3.1 ± 1.1 Gt a−1 for 1900/01–1989/90, −4.3 ± 1.0 Gt a−1 for 1970/71–2017/18, −8.3 ± 0.8 Gt a−1 for 1992/93–2017/18, and −7.6 ± 0.8 Gt a−1 for 2005/06–2017/18

Boost glacier monitoring

Glacier-mass changes are a reliable indicator of climate change. On behalf of the worldwide network of glacier observers, we urge parties to the United Nations Framework Convention on Climate Change to boost international cooperation in monitoring these changes, and to include the results in the Paris agreement’s global stocktake. Since 1960, glaciers have lost more than 9,000 gigatonnes of ice worldwide — the equivalent of a 20-metre-thick layer with the area of Spain. This melting alone — as distinct from that of the Greenland and Antarctic ice sheets — has raised global sea level by almost 3 centimetres, contributing 25–30% of the total rise (M. Zemp et al. Nature 568, 382–386; 2019). The present rate of melting is unprecedented. Several mountain ranges are likely to lose most of their glaciers this century. And we face the loss of almost all glaciers by 2300 (B. Marzeion et al. Cryosph. 6, 1295–1322; 2012). Glacier shrinkage will severely affect freshwater availability and increase the risk of local geohazards. Global sea-level rise will result in the displacement of millions of people in coastal regions and in the loss of life, livelihoods and cultural- heritage sites. The systematic monitoring of glaciers has been internationally coordinated for 125 years. Continuing to do so will document progress in limiting climate change for current and future generations