The Vulnerability and Resilience of Seagrass Ecosystems to Marine Heatwaves in New Zealand: A Remote Sensing Analysis of Seascape Metrics Using PlanetScope Imagery

Seagrasses are foundation species that provide ecosystem functions and services, including increased biodiversity, sediment retention, carbon sequestration, and fish nursery habitat. However, anthropogenic stressors that reduce water quality, impose large-scale climate changes, and amplify weather patterns, such as marine heatwaves, are altering seagrass meadow configurations. Quantifying large-scale trends in seagrass distributions will help evaluate the impacts of climate drivers on their functions and services. Here, we quantified spatiotemporal dynamics in abundances and configurations of intertidal and shallow subtidal seagrass (Zostera muelleri) meadows in 20 New Zealand (NZ) estuaries that span a 5-year period (mid/late 2016–early 2022) just before, during and after the Tasman Sea 2017/18 marine heatwave, the warmest summer ever recorded in NZ. We used high-resolution PlanetScope satellite imagery to map interseasonal seagrass extent and quantify seascape metrics across 20 estuaries along a latitudinal gradient spanning 12° in NZ. We also explored the association of changes in seagrass metrics with satellite-derived predictors such as sea surface temperature (SST), SST anomaly (SSTa), water column turbidity, and nutrient concentration. Our analyses revealed that NZ seagrass meadows varied in areal extent between years and seasons, but with no clear patterns over the 5-year period, implying resilience to large-scale stressors like the 2017/18 marine heatwave. Small-scale patterns were also dynamic, for example, patch sizes and patch configurations differed across estuaries, seasons, and years. Furthermore, seagrass patches expanded in some estuaries with increasing SST and SSTa. These results highlight dynamic seagrass patterns that likely affect local processes such as biodiversity and carbon sequestration. Our analyses demonstrate that a combination of high-resolution satellite remote sensing and seascape metrics is an efficient and novel approach to detect impacts from anthropogenic stressors, like eutrophication and climate changes, and climate extremes like cyclones and heatwaves

The formation of a subsurface anticyclonic eddy in the Peru-Chile Undercurrent and its impact on the near-coastal salinity, oxygen and nutrient distributions

The formation of a subsurface anticyclonic eddy in the Peru-Chile Undercurrent (PCUC) in January and February 2013 is investigated using a multi-platform four-dimensional observational approach. Research vessel, multiple glider and mooring-based measurements were conducted in the Peruvian upwelling regime near 12°30'S. The dataset consists of > 10000 glider profiles and repeated vessel-based hydrography and velocity transects. It allows a detailed description of the eddy formation and its impact on the near-coastal salinity, oxygen and nutrient distributions. In early January, a strong PCUC with maximum poleward velocities of ∼ 0.25 m/s at 100 to 200 m depth was observed. Starting on January 20 a subsurface anticyclonic eddy developed in the PCUC downstream of a topographic bend, suggesting flow separation as the eddy formation mechanism. The eddy core waters exhibited oxygen concentrations < 1μmol/kg, an elevated nitrogen-deficit of ∼ 17μmol/l and potential vorticity close to zero, which seemed to originate from the bottom boundary layer of the continental slope. The eddy-induced across-shelf velocities resulted in an elevated exchange of water masses between the upper continental slope and the open ocean. Small scale salinity and oxygen structures were formed by along-isopycnal stirring and indications of eddy-driven oxygen ventilation of the upper oxygen minimum zone were observed. It is concluded that mesoscale stirring of solutes and the offshore transport of eddy core properties could provide an important coastal open-ocean exchange mechanism with potentially large implications for nutrient budgets and biogeochemical cycling in the oxygen minimum zone off Peru

Geologiske interesseområder - Århus Amts nye hjemmeside om geologi

&Aring;rhus Amt har i l&oslash;bet af 2004 og&nbsp;2005 som led i den generelle&nbsp;regionplansrevision sat fokus p&aring; amtets&nbsp;geologiske interesseomr&aring;der. I&nbsp;alt 77 omr&aring;der (med tilh&oslash;rende&nbsp;underlokaliteter) er udpeget som&nbsp;omr&aring;der, der har s&aelig;rlige geologiske&nbsp;og landskabelige v&aelig;rdier. Disse omr&aring;der&nbsp;er nu beskrevet og sammenstillet&nbsp;i 77 beskrivelser, der ligger frit&nbsp;tilg&aelig;ngeligt p&aring; amtets hjemmeside

Geologi og grundvand i 3 D - GeoScene3D - nyt værktøj til præsentation

&Aring;rhus Amt har som det f&oslash;rste amt&nbsp;i Danmark valgt at offentligg&oslash;re&nbsp;sine resultater fra den omfattende&nbsp;kortl&aelig;gning af grundvandsressourcerne&nbsp;p&aring; internettet ved hj&aelig;lp af&nbsp;3D-grafik. P&aring; amtets hjemmeside er&nbsp;det muligt at bev&aelig;ge sig rundt b&aring;de&nbsp;over og under jordoverfladen og&nbsp;betragte de geologiske data fra alle&nbsp;vinkler &ndash; n&aelig;rmest som i et computerspil

Wideband corrugated feedhorns, for radar, communications, radiometry and quasi-optics

This work was supported in part by Engineering and Physical Sciences Research Council, U.K., under Grant EP/R013705/1, and in part by IAA Funding.A wide variety of desirable antenna beam patterns can be synthesized by optimal excitation and phasing of the HE11 and HE12 modes in scalar corrugated feedhorns. However, the bandwidth of such two-mode horns is often limited by modal dispersion. In this paper we introduce a class of low dispersion, two-mode feedhorns that can operate, in some cases, over operating bandwidths of 40-50%. We provide example designs that include horns with high coupling efficiency to: 1) a pure HE11 mode for single-mode excitation of corrugated pipe transmission lines; 2) a LG00 and LG02 combination for radiometry, with narrow beams; 3) a pure Laguerre Gaussian LG00 mode for quasi-optical instrumentation with constant phase centers; 4) a constant gain antenna for uniform illumination with frequency; 5) Airy patterns or “top hat” patterns for radar or communications applications, designed to maximize aperture efficiencies when used with larger reflect or lens antennas. More generally, we show methods to generate and phase multiple HE1n modes, to synthesize symmetric output beams at any desired frequency or gain.Publisher PDFPeer reviewe

Kortlægning af begravede dale - gebyrkortlægning og undersøgelsesmetoder

&Aring;rhus Amt er i lighed med landets&nbsp;&oslash;vrige amter i gang med en&nbsp;omfattende kortl&aelig;gning af grundvandsressourcerne&nbsp;i Omr&aring;der med&nbsp;S&aelig;rlige Drikkevandsinteresser&nbsp;(OSD-omr&aring;der). Disse omr&aring;der er&nbsp;beskrevet ved et antal indsatsomr&aring;der,&nbsp;for hvilke der skal udarbejdes&nbsp;indsatsplaner med henblik p&aring; beskyttelse&nbsp;af fremtidens drikkevandsressourcer

Begravede dale i Århus Amt - undersøgelse af Frijsenborg-Foldby-plateauet

I den foreg&aring;ende artikel kiggede vi&nbsp;p&aring; to af de metoder, der er benyttet&nbsp;i forbindelse med kortl&aelig;gning&nbsp;af grundvandsressourcerne i &Aring;rhus&nbsp;Amt. Der s&aring; vi, hvordan der i &Aring;rhus&nbsp;Nord og ved Hadsten ved hj&aelig;lp af&nbsp;geofysiske metoder er blevet identificeret et imponerende netv&aelig;rk&nbsp;af begravede dale, og vi sluttede&nbsp;af med at omtale, hvordan disse&nbsp;dales indfyldning p&aring; baggrund af&nbsp;fingrusanalyser er blevet henf&oslash;rt til&nbsp;forskellige glaciationer