Alfred Wegener Institute for Polar and Marine Research
Electronic Publication Information CenterNot a member yet
52828 research outputs found
Sort by
Towards a common terminology in radioglaciology
Get PDFOver the past 70 years, many different components of the cryosphere have been imaged with a variety of radar systems using increasingly sophisticated processing techniques. These systems use various pulse lengths, signal frequencies and, in some cases, modulated signals. The increasing diversity of radar systems has created the potential for confusion due to the use of non-consistent terminology. Here we provide an overview of state-of-the-science radar technologies and suggest a simplified and unified terminology for use by the cryosphere community. We recommend a terminology that is target independent but specifies the characteristics of the signal. Following this recommendation, commercial impulse systems that penetrate the subsurface should be referred to as ground-penetrating radar (GPR), and pulse radars as radio-echo sounding (RES). Continuous-wave (CW) radar systems should be referred to as ground-penetrating CW radars. We further suggest any additional characterisation of the system be expressed using descriptors that specify the platform it is mounted on (e.g. airborne) or the frequency range (e.g. HF (high frequency)) or modulation (e.g. FM (frequency modulated))
Potential of MALDI‐TOF MS‐based proteomic fingerprinting for species identification of Cnidaria across classes, species, regions and developmental stages
No full textMorphological identification of cnidarian species can be difficult throughout all life stages due to the lack of distinct morphological characters. Moreover, in some cnidarian taxa genetic markers are not fully informative, and in these cases combinations of different markers or additional morphological verifications may be required. Proteomic fingerprinting based on MALDI-TOF mass spectra was previously shown to provide reliable species identification in different metazoans including some cnidarian taxa. For the first time, we tested the method across four cnidarian classes (Staurozoa, Scyphozoa, Anthozoa, Hydrozoa) and included different scyphozoan life-history stages (polyp, ephyra, medusa) in our dataset. Our results revealed reliable species identification based on MALDI-TOF mass spectra across all taxa with species-specific clusters for all 23 analysed species. In addition, proteomic fingerprinting was successful for distinguishing developmental stages, still by retaining a species specific signal. Furthermore, we identified the impact of different salinities in different regions (North Sea and Baltic Sea) on proteomic fingerprints to be negligible. In conclusion, the effects of environmental factors and developmental stages on proteomic fingerprints seem to be low in cnidarians. This would allow using reference libraries built up entirely of adult or cultured cnidarian specimens for the identification of their juvenile stages or specimens from different geographic regions in future biodiversity assessment studies
New estimates of pan-Arctic sea ice–atmosphere neutral drag coefficients from ICESat-2 elevation data
Get PDFThe effect that sea ice topography has on the mo-
mentum transfer between ice and atmosphere is not fully
quantified due to the vast extent of the Arctic and limita-
tions of current measurement techniques. Here we present a
method to estimate pan-Arctic momentum transfer via a pa-
rameterization that links sea ice–atmosphere form drag coef-
ficients with surface feature height and spacing. We measure
these sea ice surface feature parameters using the Ice, Cloud
and land Elevation Satellite-2 (ICESat-2). Though ICESat-2
is unable to resolve as well as airborne surveys, it has a higher
along-track spatial resolution than other contemporary al-
timeter satellites. As some narrow obstacles are effectively
smoothed out by the ICESat-2 ATL07 spatial resolution, we
use near-coincident high-resolution Airborne Topographic
Mapper (ATM) elevation data from NASA’s Operation Ice-
Bridge (OIB) mission to scale up the regional ICESat-2 drag
estimates. By also incorporating drag due to open water, floe
edges and sea ice skin drag, we produced a time series of
average total pan-Arctic neutral atmospheric drag coefficient
estimates from November 2018 to May 2022. Here we have
observed its temporal evolution to be unique and not directly
tied to sea ice extent. By also mapping 3-month aggregates
for the years 2019, 2020 and 2021 for better regional anal-
ysis, we found the thick multiyear ice area directly north of
the Canadian Archipelago and Greenland to be consistently
above 2.0 × 10 −3 , while most of the multiyear ice portion of
the Arctic is typically around 1.5 × 10 −3
Postdepositional Behavior of Molybdenum in Deep Sediments and Implications for Paleoredox Reconstruction
Get PDFMolybdenum (Mo) is a trace element sensitive to oceanic redox conditions. The fidelity of sedimentary Mo as a paleoredox proxy of coeval seawater depends on the extent of Mo remobilization during postdepositional processes. Here we present the Mo content and isotope profiles for deep sediments from the Nankai Trough, Japan. The Mo signature suggests that these sediments have experienced extensive early diagenesis and hydrothermal alteration at depth. Iron (Fe)‐manganese (Mn) (oxyhydr)oxide alteration combined with Mo thiolation leads to a more than twenty‐fold enrichment of Mo within the sulfate reduction zone. Hydrothermal fluids and Mo adsorption onto Fe‐Mn (oxyhydr)oxides cause extremely negative Mo‐isotope values at the underthrust zone. These postdepositional Mo signals might be misinterpreted as expanded anoxia in the water column. Our findings highlight the importance of constraining postdepositional effects on Mo‐based proxies during paleoredox reconstruction
Evaluation of Surface Layer Stability Functions and Their Extension to First Order Turbulent Closures for Weakly and Strongly Stratified Stable Boundary Layer
Get PDFIn this study, we utilize a generalization of Monin–Obukhov similarity theory to construct first order turbulent closures for single-column models of the atmospheric boundary layer (ABL). A set of widely used universal functions for dimensionless gradients is evaluated.
Two test cases based on Large-Eddy Simulations (LES) experimental setups are considered – weakly stable ABL (GABLS1; Beare et al. in Bound Layer Meteorol 118(2):247–272,2006), and very strongly stratified ABL (van der Linden et al. in Bound Layer Meteorol
173(2):165–192, 2019). The comparison shows that approximations obtained using a linear
dimensionless velocity gradient tend to match the LES data more closely. In particular, the
EFB (Energy- and Flux- Budget) closure proposed by Zilitinkevich et al. (Bound Layer Meteorol 146(3):341–373, 2013) has the best performance for the tests considered here. We also test surface layer “bulk formulas” based on these universal functions. The same LES data are utilized for comparison. The setup showcases the behavior of surface scheme, when one assumes that the velocity and temperature profiles in ABL are represented correctly. The advantages and disadvantages of different surface schemes are revealed
The enormous repetitive Antarctic krill genome reveals environmental adaptations and population insights
Get PDFAntarctic krill (Euphausia superba) is Earth’smost abundant wild animal, and its enormous biomass is vital to
the Southern Ocean ecosystem. Here, we report a 48.01-Gb chromosome-level Antarctic krill genome, whose
large genome size appears to have resulted from inter-genic transposable element expansions. Our assembly
reveals the molecular architecture of the Antarctic krill circadian clock and uncovers expanded gene
families associated with molting and energy metabolism, providing insights into adaptations to the cold
and highly seasonal Antarctic environment. Population-level genome re-sequencing from four geographical
sites around the Antarctic continent reveals no clear population structure but highlights natural selection
associated with environmental variables. An apparent drastic reduction in krill population size 10 mya and
a subsequent rebound 100 thousand years ago coincides with climate change events. Our findings uncover
the genomic basis of Antarctic krill adaptations to the Southern Ocean and provide valuable resources for
future Antarctic research
Clathrate hydrates of air in polar ice and their importance for climate science
Get PDFclathrate hydrates are solid guest-host com- pounds, formed by small molecules (guests; e.g. N2, O2, cH4 or cO2) trapped in a crystal- line framework (host) of hydrogen-bonded water molecules (chazallon and Kuhs 2002). In natural environments, clathrate hydrates occur in deep-sea sediments and perma- frost (e.g. as methane hydrates). the first direct observations of clathrate hydrates
of air (hereinafter, air hydrates) in polar ice were made in 1982 by Shoji and Langway (1982) in the Dye-3 ice core (Greenland) using an optical microscope. Subsequently, air hydrates have been found in all deep ice cores in Greenland and Antarctica (Uchida et al. 2014)
Salinity as a tool for strain selection in recirculating land-based production of Ulva spp. from germlings to adults
Get PDFThe genus Ulva is globally distributed and has been thoroughly studied because of its functional biochemical composition,
rapid growth rates and opportunistic features, and interest in Ulva cultivation is growing worldwide. In Europe, mostly
near- and on-shore flow-through cultivation systems are used and land-based recirculating aquaculture systems (RAS) using
fresh water or artificial seawater have not been developed for Ulva. While RAS provides quality control and can be located
inland, maintenance costs are high. Using selected strains adapted to low-salinity could reduce seawater production costs
and improve the economic feasibility. Therefore, our study assessed how salinity can be used as a tool for strain selection and
optimization of functional traits. Growth rates and antioxidant activity of three species (four strains) of tubular and foliose
Ulva from the NE-Atlantic and Mediterranean (foliose: Ulva lacinulata – two geographical strains, tubular: Ulva linza and
Ulva flexuosa) were followed for three weeks at salinities ranging from 10 to 30 PSU. The tubular strains achieved optimal
growth at a lower salinity than U. lacinulata. However, growth rates of both foliose strains were higher than of tubular strains,
even at sub-optimal salinity. Therefore, U. lacinulata is a good candidate for RAS with artificial seawater, and the cost of salt
can be reduced by up to 33.3% (20 PSU) without significantly reducing the growth rate of U. lacinulata. Higher antioxidant
activity was achieved by reducing the salinity to 10 PSU for 10 days, suggesting that the functional traits of cultivated Ulva
lacinulata can be optimized prior to harvest