Hydroclimatic Controls on the Isotopic (δ18 O, δ2 H, d-excess) Traits of Pan-Arctic Summer Rainfall Events

Arctic sea-ice loss is emblematic of an amplified Arctic water cycle and has critical feedback implications for global climate. Stable isotopes (delta O-18, delta H-2, d-excess) are valuable tracers for constraining water cycle and climate processes through space and time. Yet, the paucity of well-resolved Arctic isotope data preclude an empirically derived understanding of the hydrologic changes occurring today, in the deep (geologic) past, and in the future. To address this knowledge gap, the Pan-Arctic Precipitation Isotope Network (PAPIN) was established in 2018 to coordinate precipitation sampling at 19 stations across key tundra, subarctic, maritime, and continental climate zones. Here, we present a first assessment of rainfall samples collected in summer 2018 (n = 281) and combine new isotope and meteorological data with sea ice observations, reanalysis data, and model simulations. Data collectively establish a summer Arctic Meteoric Water Line where delta H-2 = 7.6.delta O-18-1.8 (r(2) = 0.96, p 0.75 parts per thousand/degrees C) were observed at continental sites, while statistically significant temperature relations were generally absent at coastal stations. Model outputs indicate that 68% of the summer precipitating air masses were transported into the Arctic from mid-latitudes and were characterized by relatively high delta O-18 values. Yet 32% of precipitation events, characterized by lower delta O-18 and high d-excess values, derived from northerly air masses transported from the Arctic Ocean and/or its marginal seas, highlighting key emergent oceanic moisture sources as sea ice cover declines. Resolving these processes across broader spatial-temporal scales is an ongoing research priority, and will be key to quantifying the past, present, and future feedbacks of an amplified Arctic water cycle on the global climate system

Fæðuval vaðfugla í fjörum á fari um Reykjanesskaga

Háarktískir vaðfuglar ferðast um og staldra við á Íslandi á leið milli vetrar- og varpsvæða. Þeir sækja í fjörur landsins, einkum á Suðvestur- og Vesturlandi og safna forða til áframhaldandi ferðalags til varpstöðva á Grænlandi og í Kanada. Í þessari rannsókn var fæða vaðfugla á fartíma að vori skoðuð og tilraun gerð til að varpa ljósi á mikilvægustu fæðuhópa hverrar tegundar. Sérhæfing og skörun tegundanna í fæðuvali var metin og fæðuvalið borið saman við fyrirliggjandi þekkingu á fæðu á vetrarstöðvum. Almennt reyndust flestar tegundir ósérhæfðar, ásamt því að mikil skörun var í fæðuvali tegunda. Sanderlur sóttu í fjölbreytta fæðu, þó aðallega úr uppreknu þangi og seti. Tildrur átu fjölbreytta fæðu bæði úr grýttri fjöru og uppreknu þangi. Sandlóur átu aðallega burstaorma, þangflugulirfur og þangflugur en nýttu sér flesta fæðuhópa allra vaðfuglategundanna sem skoðaðar voru. Rauðbrystingar sýndu mestu sérhæfinguna og átu nær eingöngu þangdoppur, en einnig þangflugulirfur. Lóuþrælar voru ósérhæfðir og átu ána, tvívængjur og marflær. Þekking á fæðu þessara fuglastofna á fari er gloppótt og mikilvægi mismunandi fæðutegunda hefur ekki verið metið áður á þennan hátt á Íslandi. Því varpa ég hér nýju ljósi á fæðu vaðfuglastofna sem eru mikilvægur hluti íslenskra fjara og þessi skrif gætu nýst sem upplýsingar til verndunar þeirra og annars fjörulífs.High Arctic wader populations stop in Iceland on their way from wintering grounds in Europe and Africa to the high Arctic in Greenland and Canada. These populations seek sandy and muddy beaches and rocky shores on the southwest and west part of Iceland. Little is known about their diet in this sub-Arctic stopover site and whether they specialize in the same type of prey items as they do on their wintering grounds or if they are more generalized in their strategy. Resource utilization within the same community on a stop-over site is interesting and investigation of resource portioning is necessary to understand the mechanisms that influence the structure of the community. This research focused on gathering information and sampling individual birds by means of stomach flushing and stable isotope analysis, as well as stomach content analysis using dead birds to determine the most important food sources, diet and niche overlap and if the species show feeding specialization on their northward migration. Apart from the red knot, all wader species studied seemed to be generalized. All species overlapped in diet to some degree. Sanderlings were generalists feeding mostly on prey items from the wrack beds such as seaweed flies and their larvae and polychaetes from the sandy beaches. Turnstones ate a wide variety of food items, but these items were mostly from the wrack beds and the rocky shore such as seaweed fly larvae, amphipods, littorinids and barnacles. Ringed plovers mostly ate polychaeta, seaweed flies and larvae, but they did have the biggest range in stable isotopes and ate the most diverse food sources, probably due to their feeding strategy. Red knots were specialized and ate almost exclusively Littorina sp., apart from a few seaweed flies. The few dunlins that were caught ate oligochaetes, dipterans and amphipods. Very few diet studies have been performed on waders in Iceland apart from results on few collected individuals. That data and the results of this thesis are shown and compared with relevant information about wintering diets of waders.Þekkingarsetur Suðurnesj

Þróunarleg sérstaða íslenskra skógarþrasta, metin út frá hvatbera DNA

Skógarþrestir skiptast í tvær undirtegundir Turdus iliacus iliacus og T. i. coburni. T. i. coburni er undirtegund sem verpir á Íslandi og stöku sinnum í Færeyjum. Íslenska undirtegundin hefur vetursetu á Írlandi, Skotlandi, Bretlandi, norður Frakklandi og á Íberíuskaga og er töluvert stærri, dekkri og hefur gulbrúnni grunnlit í andliti, á brjósti og undirstélþökum samanborið við T. i. iliacus sem er útbreidd á meginlandi Evrópu og allt austur að 165°A, nánar tiltekið Chukotka Autonomous Okrug í Rússlandi. Ég safnaði sýnum af fuglum sem veiddir voru í Skógræktinni í Fossvogi, einangraði DNA og bar það saman við áður birtar erlendar DNA raðir. Með strikamerkingu (e. barcoding) fann ég vísbendingar fyrir því að það sé lítil sem engin aðgreining í hvatbera DNA með því að athuga hluta af COI (cytochrome c oxidase subunit I) geninu sem bendir til þess að sú aðgreining sem við sjáum í svipfari fuglanna sé fremur nýleg í þrónunarfræðilegum skilningi. Þessi aðgreining gæti hafa verið drifin áfram af náttúrulegu vali eða hröðum tilviljunakenndum breytingum sem gætu hafa átt sér stað í litlum landnámsstofni skógarþrasta á Íslandi. Því er með vissu hægt að segja að þessi gögn styðji ekki kenningu um langan aðskilnað íslenskra skógarþrasta frá öðrum skógarþröstum á meginlandi Evrasíu.The Redwing is a bird in the thrush family Turdidae. It has two subspecies Turdus iliacus iliacus and T. i. coburni. T. i. coburni breeds in Iceland and the Faroe Islands and winters in Ireland, Scotland, northern France and in Iberia. It is darker overall, larger and has buffier underparts compared to T.i iliacus which breeds in Eurasia. Data collection took place in Skógrækt Fossvogar, Reykjavík Iceland. I looked at sequence variation of the mtDNA COI (cytochrome c oxidase subunit I) used for an international barcode survey, and compared them with previously published sequences of T. i. iliacus. My data reveals that the isolated Icelandic stock in Iceland lacks the support in mtDNA gene trees for avian subspecies. However, phenotypic variation can evolve rapidly so the separation of the subspecies has most likely happened recently and even after the last cold period of the last ice age. In conclusion, there is no support in my data for old separation of the two redwing subspecies, the Icelandic redwing and the redwing on the mainland Europe

Synchronous timing of return to breedingsites in a long-distance migratory seabirdwith ocean-scale variation in migrationschedules

Background Migratory birds generally have tightly scheduled annual cycles, in which delays can have carry-over effects on the timing of later events, ultimately impacting reproductive output. Whether temporal carry-over effects are more pronounced among migrations over larger distances, with tighter schedules, is a largely unexplored question. Methods We tracked individual Arctic Skuas Stercorarius parasiticus, a long-distance migratory seabird, from eight breeding populations between Greenland and Siberia using light-level geolocators. We tested whether migration schedules among breeding populations differ as a function of their use of seven widely divergent wintering areas across the Atlantic Ocean, Mediterranean Sea and Indian Ocean. Results Breeding at higher latitudes led not only to later reproduction and migration, but also faster spring migration and shorter time between return to the breeding area and clutch initiation. Wintering area was consistent within individuals among years; and more distant areas were associated with more time spent on migration and less time in the wintering areas. Skuas adjusted the period spent in the wintering area, regardless of migration distance, which buffered the variation in timing of autumn migration. Choice of wintering area had only minor effects on timing of return at the breeding area and timing of breeding and these effects were not consistent between breeding populations. Conclusion The lack of a consistent effect of wintering area on timing of return between breeding areas indicates that individuals synchronize their arrival with others in their population despite extensive individual differences in migration strategies.Arctic Skua, Parasitic Jaeger, Stercorarius parasiticus, Migratory connectivity, Phenology, Annual cycle,Carry-over effects

Hydroclimatic controls on the isotopic (δ¹⁸ O, δ² H, d-excess) traits of pan-Arctic summer rainfall events

Abstract Arctic sea-ice loss is emblematic of an amplified Arctic water cycle and has critical feedback implications for global climate. Stable isotopes (δ¹⁸O, δ²H, d-excess) are valuable tracers for constraining water cycle and climate processes through space and time. Yet, the paucity of well-resolved Arctic isotope data preclude an empirically derived understanding of the hydrologic changes occurring today, in the deep (geologic) past, and in the future. To address this knowledge gap, the Pan-Arctic Precipitation Isotope Network (PAPIN) was established in 2018 to coordinate precipitation sampling at 19 stations across key tundra, subarctic, maritime, and continental climate zones. Here, we present a first assessment of rainfall samples collected in summer 2018 (n = 281) and combine new isotope and meteorological data with sea ice observations, reanalysis data, and model simulations. Data collectively establish a summer Arctic Meteoric Water Line where δ²H = 7.6⋅δ¹⁸O–1.8 (r² = 0.96, p < 0.01). Mean amount-weighted δ¹⁸O, δ²H, and d-excess values were −12.3, −93.5, and 4.9‰, respectively, with the lowest summer mean δ¹⁸O value observed in northwest Greenland (−19.9‰) and the highest in Iceland (−7.3‰). Southern Alaska recorded the lowest mean d-excess (−8.2%) and northern Russia the highest (9.9‰). We identify a range of δ¹⁸O-temperature coefficients from 0.31‰/°C (Alaska) to 0.93‰/°C (Russia). The steepest regression slopes (>0.75‰/°C) were observed at continental sites, while statistically significant temperature relations were generally absent at coastal stations. Model outputs indicate that 68% of the summer precipitating air masses were transported into the Arctic from mid-latitudes and were characterized by relatively high δ¹⁸O values. Yet 32% of precipitation events, characterized by lower δ¹⁸O and high d-excess values, derived from northerly air masses transported from the Arctic Ocean and/or its marginal seas, highlighting key emergent oceanic moisture sources as sea ice cover declines. Resolving these processes across broader spatial-temporal scales is an ongoing research priority, and will be key to quantifying the past, present, and future feedbacks of an amplified Arctic water cycle on the global climate system