Alfred Wegener Institute for Polar and Marine Research
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Atmospheric destabilization leads to Arctic Ocean winter surface wind intensification
Get PDFThe surface-amplified winter warming over the Arctic Ocean is accompanied by a pronounced intensification of near-surface winds, simulated by climate models and emerging in reanalysis data. Here, the influences of sea-ice decline, wind changes aloft, and atmospheric stability are revisited based on CMIP6 historical and high-emission scenario and ERA5 reanalysis data. Spatial trend patterns suggest that near-surface wind intensification over the inner Arctic Ocean in winter is largely driven by an increasing downward momentum transfer due to a weakening atmospheric stratification. In contrast, a near-surface wind intensification in summer appears to be largely driven by accelerating winds aloft, amplified in a high-emission future by decreasing surface roughness due to sea-ice decline. In both seasons, differences in near-surface wind-speed trends are closely linked to atmospheric stability trends. Models suggest that by 2100 the lower troposphere may become as unstable in winter as in summer, implying a fundamental regime shift of the Arctic winter boundary layer
Spatial distribution of small microplastics in the Norwegian Coastal Current
Get PDFHigh concentrations of microplastic (MP) particles have been reported in the Arctic Ocean. However, studies on the high-resolution lateral and vertical transport of MPs from the European waters to the Arctic are still scarce. Here, we provide information about the concentrations and compositions of MPs in surface, subsurface, and deeper waters (300 μm), and overall, SMPs 80 % of all detected MPs. However, no statistically significant geographical patterns were observed in SMP concentrations in surface/subsurface seawaters between the six sampling transects, suggesting a relatively homogeneous horizontal distribution of SMPs in the upper ocean within the NCC/Norwegian Atlantic Current (NwAC) interface. The Lagrangian particle dispersal simulation model further enabled us to assess the large-scale transport of MPs from the Northern European waters to the Arctic
Evaluating the global ocean biogeochemistry models used in the Global Carbon Budget with the International Ocean Model Benchmarking (IOMB) System
Get PDFCircumarctic land cover diversity considering wetness gradients
Get PDFLand cover heterogeneity information considering soil wetness across the entire Arctic tundra is of interest for a wide range of applications targeting climate change impacts and ecological research questions. Patterns are potentially linked to permafrost degradation and affect carbon fluxes. First, a land cover unit retrieval scheme which provides unprecedented detail by fusion of satellite data using Sentinel-1 (synthetic aperture radar) and Sentinel-2 (multispectral) was adapted. Patterns of lakes, wetlands, general soil moisture conditions and vegetation physiognomy are interpreted at 10 m nominal resolution. Units with similar patterns were identified with a k-means approach and documented through statistics derived from comprehensive in situ records for soils and vegetation (more than 3500 samples). The result goes beyond the capability of existing land cover maps which have deficiencies in spatial resolution, thematic content and accuracy, although landscape heterogeneity related to moisture gradients cannot be fully resolved at 10 m. Wetness gradients were assessed, and measures for landscape heterogeneity were derived north of the treeline. About 40 % of the area north of the treeline falls into three units of dry types with limited shrub growth. Wetter regions have higher land cover diversity than drier regions. An area of 66 % of the analysed Arctic landscape is highly heterogeneous with respect to wetness at a 1 km scale (representative scale of frequently used regional land cover and permafrost modelling products). Wetland areas cover 9 % and moist tundra types 32 %, which is of relevance for methane flux upscaling
Seasonality of spectral radiative fluxes and optical properties of Arctic sea ice during the spring–summer transition
Get PDFThe reflection, absorption, and transmittance of shortwave solar radiation by sea ice play crucial roles in
physical and biological processes in the ice-covered Arctic Ocean and atmosphere. These sea-ice optical
properties, particularly during the melt season, significantly impact energy fluxes within and the total
energy budget of the coupled atmosphere-ice-ocean system. We analyzed data from autonomous drifting
stations to investigate the seasonal evolution of the spectral albedo, transmittance, and absorptivity for
different sea-ice, snow, and surface conditions measured during the MOSAiC expedition in 2019–2020. The
spatial variability of these properties was small during spring and increased strongly after melt onset on May
26, 2020, when liquid water content on the surface increased, largely accounting for the enhanced variability.
The temporal evolution of surface albedo and sea-ice transmittance was mostly event-driven, thus containing
episodic elements. Melt ponds reduced the local surface albedo by 31%–45%. Over the melting season, single
ponding events increased the energy deposition of the sea ice by 35% compared to adjacent bare ice. Thus,
single melt ponds may impact the summer energy budget as much as seasonal evolution over 1 month.
Absorptivity and transmittance showed strong temporal and spatial variabilities independently of surface
conditions, possibly due to the different internal sea-ice properties and under-ice biological processes. The
differences in seasonal evolution shown for different sea-ice conditions strongly impacted the partitioning
of shortwave solar radiation.This study shows that the formation and development of melt ponds, in reducing
albedo by a third of bare ice sites, can notably increase the total summer heat deposition.The vastly different
seasonal evolutions, different sea-ice conditions, and timing and duration of ponding events need to be
considered when comparing local in-situ observations with large-scale satellite remote sensing datasets,
which we suggest can help to improve numerical models
Monitoring plankton and hydrography in Potter Cove: observing a changing system during 30 years
Get PDFAntarctic ecosystems are experiencing significant environmental changes, leading to shifts in hydrography, plankton abundance, and community composition, potentially affecting the entire food web. Since the early 1990s, the Coastal Ecology Programme of the Argentinian Antarctic Institute, in collaboration with the Alfred Wegener Institute from Bremerhaven, Germany, has been monitoring coastal hydrography and plankton dynamics. Over nearly 30 years, observations at Potter Cove (25 de Mayo/King George Island, South Shetlands) revealed notable transformations, such as the retreat of the surrounding Fourcade Glacier, and its evolution from a tidal to a land-terminated glacier in 2016, coinciding with a consistent rise in temperature. In addition, Potter Cove phytoplankton, characterized by sparse abundances and occasional blooms during colder seasons in the decades between early 1990’s and 2010, evidenced a shift occurring post-2010, marked by more frequent phytoplankton blooms. However, in warmer-than-average years of the last decade, the plankton community composition skewed toward nanosized phytoplankton, including species typical of Subantarctic regions. It was demonstrated in summer 2020 during two marine heatwave events through in situ monitoring of plankton community. These findings underscore the necessity for ongoing monitoring and research to comprehend the implications of a warming climate on Antarctic ecosystems. In this sense, in January 2024, as part of the ROMA (Argentinian Network for Observations of Coastal Marine Systems), an automated coastal station was deployed in Potter Cove to gather hydrographic and meteorological data. Similarly, a station with additional sensors for chlorophyll and oxygen concentrations has been operational since 2023 in the Beagle Channel, a Subantarctic coastal area, augmenting our understanding of oceanic changes under global warming scenarios. Next year two Lander moorings will be deployed at 30 m depth in both sites, to collect data on salinity, temperature, dissolved oxygen, chlorophyll and currents. These initiatives are pivotal for bridging data and knowledge gaps and advancing our comprehension of oceanic shifts
How are the impacts of multiple anthropogenic drivers considered in marine ecosystem service research? A systematic literature review
Get PDFIn recent decades, great research efforts have been made to understand how specific anthropogenic drivers impact coastal marine ecosystems and their services. Nevertheless, we still lack a synthesis of the existing knowledge on single and multiple anthropogenic drivers impacts to coastal marine systems, which is necessary to guide future work. The objective of this paper is to assess the current knowledge on the impacts of anthropogenic drivers and their interactions on coastal marine ecosystem services, with emphasis on abiotic drivers as dissolved nutrients (eutrophication or de-eutrophication), temperature (warming), pH (acidification) and oxygen (hypoxia). We performed a systematic review of the literature consisting of 164 papers using the PRISMA method (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). We only include English-written papers, we exclude non-English papers to avoid potential errors in representing or interpreting scientific information due to language limitations among the authors. The results show that coastal marine ecosystem service research has largely focused on single drivers, while multiple driver assessments are less common. Assessments partially integrate multiple driver complexity, but they do not consider (1) relations and feedbacks between drivers; 2() social processes dynamics; and (3) temporal and spatial scales. Synthesis and applications. We have reviewed the current scientific knowledge on how human drivers affect coastal marine ecosystem services. We found that understanding the combined effects of different drivers and considering various time and space scales is still a pending issue. Ignoring multiple drivers, their interactions and time and space scales limits our understanding of reality, and results in high levels of uncertainty. This affects policies and actions, as they rely on uncertain information. Thus, incomplete knowledge leads to poor management of coastal ecosystem services. To improve this, we propose research framework to better consider multiple drivers and time and space factors
A simple method of purifying authigenic 10Be from sediments for AMS-analysis
Get PDFThe cosmogenic radionuclide 10Be is used for a variety of applications, its analysis however requires laborious purification methods. We developed a simple purification protocol for Be from sediment samples that works without strongly hazardous chemicals or time consuming and expensive ion exchange columns. The combination of hydroxide precipitations and precipitation in NaHCO3 was compared to an established protocol of hydroxide precipitations and ion exchange columns. The new method has a slightly lower Be-yield and purity of the resulting samples. However, this does not have a significant influence on performance during AMS-measurement where both methods performed equally well. The avoidance of column chromatography reduces sample preparation costs and space requirements in the lab allowing for more samples to be prepared simultaneously
Life Cycles and Polycyclicity of Mega Retrogressive Thaw Slumps in Arctic Permafrost Revealed by 2D/3D Geophysics and Long‐Term Retreat Monitoring
Get PDFMega retrogressive thaw slumps (MRTS, >106 m3) are a major threat to Arctic infrastructure, alter regional biogeochemistry, and impact Arctic carbon budgets. However, processes initiating and reactivating MRTS are insufficiently understood. We hypothesize that MRTS preferentially develop a polycyclic behavior because the material is thermally and mechanically prepared for subsequent generation failure. In contrast to remote sensing, geophysical reconnaissance reveals the inner structure and relative thermal state of MRTS decameters beneath slump surfaces, potentially controlling polycyclicity. Based on their life cycle development, five (M)RTS were studied on Herschel Island, an MRTS hotspot on the Canadian Beaufort coast. We combine >2 km of electrical resistivity tomography (ERT), 500 m of ground-penetrating radar (GPR) and annual monitoring of headwall retreat from 2004 to 2013 to reveal the thermal state, internal structure, and volume loss of slumps. ERT data were calibrated with unfrozen-frozen transitions from frost probing of active layer thickness and shallow boreholes. In initial stage MRTS, ERT displays surficial thermal perturbations a few meters deep, coincident with recent mud pool and mud flow development. In early stage polycyclic MRTS, ERT shows decameter deep-reaching thermal perturbations persisting even 300 years after the last activation. In peak-stage polycyclic MRTS, 3D-ERT highlights actively extending deep-reaching thermal perturbations caused by gully incisions, mud slides and mud flows. GPR and headwall monitoring reveal structural disturbance by historical mud flows, ice-rich permafrost, and a decadal quantification of headwall retreat and slump floor erosion. We show that geophysical signatures identify long-lasting thermal and mechanical disturbances in MRTS predefining their susceptibility to polycyclic reactivation