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    Wyświetlanie 1-15 z 15
    Tytuł:
    On the buoyant sub-surface salinity maxima in the Gulf of Riga
    Autorzy:
    Liblik, T.
    Skudra, M.
    Lips, U.
    Powiązania:
    https://bibliotekanauki.pl/articles/48990.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    thermohaline structure
    Riga Gulf
    water column
    temperature
    salinity
    stratification
    water exchange
    intrusion
    Opis:
    Thermohaline structure in the Gulf of Riga (GoR) was investigated by a multiplatform measurement campaign in summer 2015. Stratification of the water column was mainly controlled by the temperature while salinity had only a minor contribution. Buoyant salinity maxima with variable strength were observed in the intermediate layer of the Gulf of Riga. The salinity maxima were likely formed by a simultaneous upwelling—downwelling event at the two opposite sides of the Irbe strait. The inflowing salty water did not reach the deeper (> 35 m) parts of the gulf and, therefore, the near-bottom layer of the gulf remained isolated throughout the summer. Thus, the lateral water exchange regime in the near bottom layer of the Gulf of Riga is more complicated than it was thought previously. We suggest that the occurrence of this type of water exchange resulting in a buoyant inflow and lack of lateral transport into the near-bottom layers might contribute to the rapid seasonal oxygen decline in the Gulf of Riga
    Źródło:
    Oceanologia; 2017, 59, 2
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Inflow of Atlantic-origin waters to the Barents Sea along glacial troughs
    Autorzy:
    Matishov, G.G.
    Matishov, D.G.
    Moiseev, D.V.
    Powiązania:
    https://bibliotekanauki.pl/articles/47953.pdf
    Data publikacji:
    2009
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    thermohaline
    bathymetry
    Atlantic-origin water
    Barents Sea
    water mass
    circulation
    climate
    glacial trough
    Opis:
    This paper discusses the role of glacial shelf topography in the formation of general oceanological and biological mechanisms in the Barents Sea. Analysis of geomorphological data and oceanographic observations obtained on board MMBI research vessels in 2001–08 has shown that: fluxes of Atlantic-origin waters pass along glacial troughs; the inflow of Atlantic waters to the Barents Sea from the west increased from 2001t ill 2007, although this advection began to weaken in 2008; vertical and horizontal thermohaline gradients intensified during the investigated period; a warm period similar to that of the 1930s was observed in the Barents Sea at the beginning of the 21st century.
    Źródło:
    Oceanologia; 2009, 51, 3; 321-340
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Application of a sigma-coordinate baroclinic model to the Baltic Sea
    Autorzy:
    Jankowski, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/47974.pdf
    Data publikacji:
    2002
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    thermohaline variability
    numerical modelling
    sigma-coordinate model
    Baltic Sea
    water circulation
    hydrological parameter
    Źródło:
    Oceanologia; 2002, 44, 1
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Variability in the saline water exchange between the Baltic and the Gulf of Gdańsk by the σ-coordinate model
    Autorzy:
    Jankowski, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/48078.pdf
    Data publikacji:
    2003
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    coastal zone
    variability
    thermohaline variability
    water exchange
    saline water
    Baltic Sea
    mass exchange
    Gdansk Gulf
    Opis:
    A three-dimensional baroclinic σ–coordinate model was applied to study the circulation and thermohaline variability in the coastal zone in the south-eastern Baltic Sea. The model is based on the Princeton Ocean Model code of Blumberg & Mellor (1987), known as POM, and has the horizontal resolution of ∼5 km and 24 σ-levels in the vertical. The hydrodynamic conditions and variability of water and salt exchange between the Gulf of Gdańsk and the Baltic Proper, and the renewal of water masses in the Gulf of Gdańsk due to atmospheric forcing are analyzed. The numerical simulations were performed with real atmospheric forcings as well as with homogeneous (spatially uniform) wind fields over the whole Baltic Sea. The numerical simulations showed that the atmospheric forcing (winds) can play a significant role in shaping the renewal of bottom saline waters in the Gulf of Gdańsk. Two regions of inflow/outflow of saline waters responsible for the salinity regime were located. The overall water exchange between the Gulf and the Baltic Proper as well as the exchange of saline bottom waters appear to be strongly dependent on wind conditions. The net flux of water of salinity >9 PSU is of the order of 48 000–100000 m3 s−1. SE, E, S and NE winds were found to exert the greatest influence on salinity conditions in the Gulf of Gdańsk. Estimates of saline (salinity >9 PSU) water residence time based on the model simulation yielded values from 46 days for SE winds to 153 days for NW winds.
    Źródło:
    Oceanologia; 2003, 45, 1
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Causes and course of climate change and its hydrological consequences in the Greater Poland region in 1951-2020
    Autorzy:
    Marsz, Andrzej A.
    Sobkowiak, Leszek
    Styszyńska, Anna
    Wrzesiński, Dariusz
    Powiązania:
    https://bibliotekanauki.pl/articles/15804430.pdf
    Data publikacji:
    2022
    Wydawca:
    Uniwersytet im. Adama Mickiewicza w Poznaniu
    Tematy:
    rapid climate shift
    cause of warming up
    thermohaline circulation
    water balance
    Polska
    North Atlantic
    Opis:
    The paper presents effects of changes in climatic elements in the Greater Poland region (Poland), their causes and consequences for shaping the water balance of this area, copying with the most severe water deficit in Poland. The study period covers 70 years (1951–2020). The research identified an abrupt and significant change in the climate of Greater Poland, which started between 1987 and 1989, concerning not only air temperature but also a wider spectrum of climatic elements. The change in the state of the climate, which covers the entire Atlantic-Eurasian circulation sector, re-sults from a sudden change in the macro-circulation conditions in the middle troposphere (500 hPa). The reason for the change in the mid-tropospheric circulation is an equally abrupt and simultaneous change in the intensity of the ocean heat transport by the North Atlantic thermohaline circulation (NA THC). Climate change observed in Greater Poland is manifested in an increase in sunshine duration (SD) and air temperature, a decrease in relative humidity, a change in the cloud structure, and an increase in the degree of sky coverage. The main, physical reason for an increase in air tempera-ture is a rapid and strong increase in SD in the warm half-years, which began after 1988, and a significant increase in the frequency of positive North Atlantic Oscillation (NAO) phases in winters. The ongoing climate change entails various effects, among which the most important is considered to be hydrological consequences. The water balance of Greater Poland is becoming increasingly unfavourable, mainly as a result of a rapid increase in field evaporation.
    Źródło:
    Quaestiones Geographicae; 2022, 41, 3; 183-206
    0137-477X
    2081-6383
    Pojawia się w:
    Quaestiones Geographicae
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Impact of a dipole on the phytoplankton community in a semi-enclosed basin of the Southern Gulf of California, Mexico
    Autorzy:
    Duran-Campos, E.
    Monreal-Gomez, M.A.
    Salas de Leon, D.A.
    Coria-Monter, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/47595.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    phytoplankton
    chlorophyll a
    dipole impact
    horizontal distribution
    thermohaline
    geostrophic flow
    dinoflagellate
    California Gulf
    Mexico
    Źródło:
    Oceanologia; 2019, 61, 3
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Linear stability effect of densely distributed porous medium and Coriolis force on Soret driven ferrothermohaline convection
    Autorzy:
    Sekar, R.
    Murugan, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/264456.pdf
    Data publikacji:
    2018
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    siła Coriolisa
    model Darcy'ego
    efekt Soreta
    ferrofluid
    Coriolis force
    Darcy model
    Soret effect
    thermohaline convection
    Opis:
    The effect of Coriolis force on the Soret driven ferrothermohaline convection in a densely packed porous medium has been studied. A linear stability analysis is carried out using normal mode technique. It is found that stationary convection is favorable for the Darcy model, therefore oscillatory instability is studied. A small thermal perturbation is applied to the basic state and linear stability analysis is used for which the normal mode technique is applied. It is found that the presence of a porous medium favours the onset of convection. The porous medium is assumed to be variable and the effect of the permeable parameter is to destabilize the system. The present work has been carried out both for oscillatory as well as stationary instabilities. The results are depicted graphically.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2018, 23, 4; 911-928
    1734-4492
    2353-9003
    Pojawia się w:
    International Journal of Applied Mechanics and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Thin chlorophyll layer concomitant of the thermohaline intrusion in the confluence of the Gulf Stream and Labrador Current (a case study)
    Autorzy:
    Karabashev, G.S.
    Powiązania:
    https://bibliotekanauki.pl/articles/48303.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    fluorometer
    chlorophyll fluorescence
    sea water
    temperature
    coloured dissolved organic matter
    vertical distribution
    thermohaline
    sea water intrusion
    Labrador Current
    Źródło:
    Oceanologia; 2019, 61, 4
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Response of Eastern Indian Ocean (ODP Site 762B) benthic foraminiferal assemblages to the closure of the Indonesian seaway
    Autorzy:
    Rai, A.K.
    Singh, V.B.
    Powiązania:
    https://bibliotekanauki.pl/articles/48495.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    Indian Ocean
    benthic foraminifera
    productivity
    upwelling
    oligotrophic water
    surface water
    Pliocene
    atmospheric circulation
    ocean circulation
    thermohaline circulation
    Źródło:
    Oceanologia; 2012, 54, 3
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Distribution of phytoplankton along the thermohaline gradient in the North-Eastern Adriatic channel; winter aspect
    Autorzy:
    Vilicic, D.
    Kuzmic, M.
    Bosak, S.
    Silovic, T.
    Hrustic, E.
    Buric, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/47482.pdf
    Data publikacji:
    2009
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    Adriatic Sea
    chlorophyll
    diatom
    dinoflagellate
    distribution
    nutrient
    oligotrophic water
    phytoplankton composition
    picoplankton
    salinity
    temperature
    thermohaline
    transition zone
    water transparency
    Opis:
    The distribution of phytoplankton and its relation to the hydrographic features in the north-eastern Adriatic was investigated in February 2008. The area of interest included a thermohaline gradient in the channel situated between the coast and the islands lying parallel to the coast. The gradient is controlled by the influx of oligotrophic karstic riverine water at the south-eastern end,subma rine springs in the middle part,an d warmer offshore waters at the north-western end of the channel. The change of temperature and salinity in the estuarine transition zone was accompanied by abundant diatoms and dinoflagellates below the halocline,with dominant chain-forming diatoms (Chaetoceros, Bacteriastrum) in abundances reaching 5×105 cells dm−3. The impact of coastal submarine springs detected by infrared remote sensing resulted in the growth of cyanobacteria in the nitrogen-depleted surface waters. The greater contribution of picoplankton, as well as of nanoplanktonic coccolithophorids and cryptophytes,in the outer channel system indicated their preference for oligotrophic conditions. Flow cytometric counts of nanophytoplankton were 10–30 times greater than inverted microscope counts. Cyanobacteria were about five times more abundant than picoeukaryotes. The study demonstrates how different techniques (remote sensing and in situ investigations) can be useful in understanding the biological and hydrographic set-up in the specific oligotrophic eastern Adriatic coastal environment.
    Źródło:
    Oceanologia; 2009, 51, 4
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Nutrient flux fuels the summer primary productivity in the oligotrophic waters of the Gulf of Aqaba, Red Sea
    Autorzy:
    Badran, M.I.
    Rasheed, M.
    Manasrah, R.
    Al-Najjar, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/47744.pdf
    Data publikacji:
    2005
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    Aqaba Gulf
    biological stress
    diffusion model
    chlorophyll a
    oligotrophic water
    primary productivity
    thermohaline stratification
    nutrient flux
    Red Sea
    Opis:
    The thermohaline characteristics of the Gulf of Aqaba, Red Sea, depict a welldefined seasonal pattern of winter mixing from December to April and summer stratification from May to November. This thermohaline structure is a major controlling factor of the nutrient, chlorophyll a and primary productivity seasonal cycles. The nitrate and chlorophyll a concentration records generated down to 200 m at a vertical resolution of 25 m – weekly during 1994, 1995 and every two weeks from April 1997 through to December 2000 – are employed to assess the nitrogen flux across the summer thermocline of the Gulf of Aqaba. The flux calculations are based on a simple diffusion model that incorporates the physical stress eddy diffusivity factor Kz and a biological stress factor k. Both Kz and k are calculated using the Michaelis-Menten equation and the nitrate concentration gradient. The total nitrate flux of the Gulf of Aqaba during the seven summer months (May–November) is estimated at 0.52 moleN m−2. In relation to established primary productivity values (75.5 gC m−2 (May November)−1) and the generated chlorophyll a records, this yields an f fraction of new to total primary production of 0.50. This relatively high f value is discussed with respect to the geophysical characteristics of the Gulf of Aqaba and similar oceanic basins. The remaining 50% is accounted for by cross-sectional flow from the relatively nutrientrich coral reef coastal habitat and rapid recycling, triggered by high irradiance and water temperature.
    Źródło:
    Oceanologia; 2005, 47, 1
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mixing characteristics of the subarctic front in the Kuroshio-Oyashio confluence region
    Autorzy:
    Ke-Lan, Z.
    Xi, C.
    Ke-Feng, M.
    Dong, H.
    Sen, H.
    Yan, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/49009.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    Subarctic Front
    Kuroshio-Oyashio confluence region
    sea surface temperature
    salinity
    topography
    geostrophic flow
    thermohaline
    structural characteristics
    turbulent mixing
    Źródło:
    Oceanologia; 2019, 61, 1
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Distinctive features of water exchange across the Słupsk Sill (a full-scale experiment)
    Autorzy:
    Paka, V.
    Golenko, N.
    Korzh, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/47795.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    Sopot
    water exchange
    thermohaline structure
    Slupsk Sill
    saline water
    conference
    Baltic Sea
    high-resolution transect
    inflow water
    brackish water
    Opis:
    The flows of brackish waters in the upper layer and saline waters in the lower layer meet above the Słupsk Sill, which makes this one of the most significant features of the Baltic Sea, controlling as it does the ventilation of the deep basins in its central region. Earlier high-resolution measurements using towed scanning probes conducted here for more than ten years had revealed the complexity and variability of the water dynamics in this area. Mapping surveys repeated in quick succession are needed to study the water exchange in such an area. A survey of this kind was attempted in October 2003 during the 57th cruise of the r/v ‘Professor Shtokman’. Three surveys were carried out in the areas of the Słupsk Sill, the eastern Bornholm Basin, and the western Słupsk Furrow by means of a scanning probe towed along closely-spaced transects. The water structure around the sill was different each time, despite the rather short time gaps between the surveys. As follows from the data analysis, during the first survey, the saline Bornholm waters flowed over the sill as an axially symmetrical jet and entrained the adjacent freshened cold waters of the intermediate layer. In ten days, this joint flow displaced to the southern flank of the sill and propagated in the Słupsk Furrow along its southern border, with the dense core of saline waters gradually moving over the bottom to the northern border. Concurrently, the contrary flow of the main volume of cold freshened waters, originating from northern areas and leaving the Baltic Sea, was pushed away from the southern wall of the furrow and blocked at a significant distance from the sill. In three days, the blocked waters forced their way through towards its northern flank. Just below these waters, waters of elevated salinity were found above the eastern slope of the sill at the depth of its ridge, while waters of a similar salinity occurred below the depth of the ridge above the western slope of the sill. There were no indications of intensive overflow in the central and southern areas of the sill. Accordingly, the return flow of Bornholm waters across the sill became possible.
    Źródło:
    Oceanologia; 2006, 48, S
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    O związkach między intensywnością cyrkulacji termohalinowej na Atlantyku Północnym a sumami opadów w Hornsundzie (Spitsbergen)
    The relationship between intensity of thermohaline circulation on the North Atlantic and precipitation totals at Hornsund (Spitsbergen)
    Autorzy:
    Marsz, A. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/260812.pdf
    Data publikacji:
    2016
    Wydawca:
    Stowarzyszenie Klimatologów Polskich
    Tematy:
    Północny Atlantyk
    THC (cyrkulacja termohalinowa)
    sumy opadów
    powierzchnia zlodzona
    Spitsbergen
    Hornsund
    North Atlantic
    THC (Thermohaline Circulation)
    precipitation totals
    sea-ice extent
    Opis:
    W pracy omówiono związki rocznych i kwartalnych sum opadów w Hornsundzie z intensywnością składowej powierzchniowej cyrkulacji termohalinowej (THC) na Atlantyku Północnym. Fazę i intensywność THC opisuje wskaźnik oznaczony jako DG3L. Analizy wykazują, że związki takie, silnie rozciągnięte w czasie, istnieją. Związki rocznych sum opadów oraz sum opadów w drugim półroczu (lipiec-grudzień) z THC są związkami pośrednimi. Wraz ze zwiększoną dostawą ciepła z transportem Wód Atlantyckich na północ, do Arktyki, rosną w wodach mórz Grenlandzkiego i Barentsa zasoby ciepła, w związku z czym wzrasta temperatura wody powierzchniowej (SST) i maleje pokrywa lodowa. Tym samym wzrasta powierzchnia wód wolnych od lodów, a powierzchnia morza ma wyższą temperaturę. Oba procesy prowadzą do wzrostu natężenia strumieni ciepła i pary wodnej z oceanu do atmosfery, co powoduje wzrost temperatury powietrza (SAT). Wzrost SAT prowadzi do podniesienia wysokości tropopauzy. W rezultacie ciągu procesów sterowanych przez zmienność THC powstają sprzyjające warunki do wzrostu sum opadów w okresie występowania zmniejszonej powierzchni lodów i silnej konwekcji w atmosferze (wzrost wodności i miąższości chmur). Te same procesy wyjaśniają wzrost udziału sum opadów ciekłych w sumie rocznej opadów w Hornsundzie oraz wystąpienie dodatniego trendu sum opadów. Opóźnienie (~6 lat) reakcji sum opadów względem zmian natężenia THC wynika z opóźnionego, w stosunku do przebiegu wskaźnika DG3L, przejścia cyrkulacji atmosferycznej nad Arktyką z reżimu cyrkulacji antycyklonalnej do reżimu cyrkulacji cyklonalnej. Zwiększenie frekwencji cyklonów nad Arktyką, poprzez wzrost częstości wypadania opadów frontalnych również sprzyja wzrostowi sum opadów. Bardziej rozszerzona analiza wskazuje, że zmienność THC reguluje, poprzez wzrost temperatury powietrza, sum opadów i zmianę struktury opadów (stałe/ ciekłe) również przebieg procesów ewolucji geosystemów lądowych.
    The work discusses relationship between total annual and quarterly precipitation in Hornsund and intensity of surface component of thermohaline circulation (THC) on the North Atlantic. Phase and intensity of THC describes index marked as DG3L. Analysis shows that there are such dependencies, significantly extended in time. Relations between THC and total annual precipitation and sums of precipitation in second half of the year (July-December) are indirect dependencies. Together with increased heat supply with transport of Atlantic Water north to the Arctic, grow heat resources in waters of the Greenland and Barents seas. As a result, SST increases and decreases ice extent. Thereby increasing area of water free of ice cover and sea surface has a higher temperature. Both processes leads to an increase in intensity of heat flux and water vapor from ocean into atmosphere, causing an increase in air temperature (SAT). An increase in SAT leads to raise height of tropopause. As a result of a sequence of processes controlled by volatility of THC are generated favorable conditions for an increase of sum of precipitation during periods of reduced sea ice extent and strong convection into atmosphere (an increase in water content and thickness of clouds). These same processes explain an increase sum of liquid precipitation in annual precipitation structure in Hornsund and an occurrence of positive trend of sum of precipitation. Occurring delay (~ 6 years) reacting sum of precipitation in relation to course of indicator, that characterizes intensity variations of THC results from retarded, with respect to course of indicator DG3L, transition of atmospheric circulation over the Arctic from anticyclonic circulation regime to cyclonic circulation regime. Increased frequency of cyclones occurrence over the Arctic, through an increase in frequency of falling out frontal precipitation also favors growth of sum of precipitation. More extended analysis indicates that variability of THC regulates, by an increase in air temperature, total precipitation and change in precipitation structure (solid / liquid) and processes of evolution of land geosystems.
    Źródło:
    Problemy Klimatologii Polarnej; 2016, 26; 17-36
    1234-0715
    Pojawia się w:
    Problemy Klimatologii Polarnej
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Model zmian powierzchni lodów morskich Arktyki (1979-2013) – zmienne sterujące w modelu „minimalistycznym” i ich wymowa klimatyczna
    Model of changes in the Arctic sea-ice extent (1979-2013) – variables steering the 'minimalist' model and their climatic significance
    Autorzy:
    Marsz, A. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/260796.pdf
    Data publikacji:
    2015
    Wydawca:
    Stowarzyszenie Klimatologów Polskich
    Tematy:
    Arktyka
    lody morskie
    zmiany powierzchni lodów
    czynniki sterujące
    model
    cyrkulacja termohalinowa
    cyrkulacja atmosferyczna
    Arctic
    sea ice
    ice extent changes
    steering variables
    thermohaline circulation
    atmospheric circulation
    Opis:
    Praca omawia model zmian powierzchni zlodzonej Arktyki typu „białej skrzynki”, opierający się na dwu zmiennych niezależnych – wskaźniku oznaczonym jako DG3L, który charakteryzuje intensywność cyrkulacji termohalinowej (THC) na Atlantyku Północnym i wskaźniku D, który charakteryzuje cyrkulację atmosferyczną nad Arktyką. Objaśnienie konstrukcji obu wskaźników i wartości ich szeregów czasowych przedstawione jest w załącznikach Z1 i Z2. Okres opracowania obejmuje lata 1979-2013 i jest limitowany dostępnością danych o zmianach powierzchni lodów morskich w Arktyce. Model liniowy opierający się na tych zmiennych objaśnia ~72% wariancji rocznej powierzchni zlodzonej w Arktyce i powyżej 65% wariancji powierzchni zlodzonej w marcu (maksimum rozwoju powierzchni lodów) i wrześniu (minimum). Główną rolę w kształtowaniu tej zmienności odgrywa zmienność cyrkulacji termohalinowej, rola cyrkulacji atmosferycznej jest niewielka i wykazuje silną zmienność sezonową. Analiza tego modelu wykazała, że rzeczywiste zależności są nieliniowe, a zmiany pokrywy lodowej zachodzą w dwu odrębnych reżimach – „ciepłym” i „chłodnym”. Reżim „ciepły” funkcjonuje w sytuacji, gdy THC jest bardziej intensywna niż przeciętnie (wskaźnik DG3L > 0). Dochodzi wtedy do szybkiego spadku powierzchni lodów w okresie ciepłym – zwłaszcza we wrześniu i powolnego spadku rozmiarów pokrywy lodowej w marcu, cyrkulacja atmosferyczna w tym reżimie odgrywa istotną rolę w kształtowaniu zmian powierzchni lodów. Spadek natężenia THC poniżej przeciętnej (DG3L ≤ 0), z opóźnieniem około 6.letnim prowadzi, do przejścia do reżimu „chodnego”. W reżimie chłodnym następuje szybki przyrost powierzchni lodów w okresie ciepłym i bardzo powolny wzrost powierzchni lodów w marcu, rola cyrkulacji atmosferycznej w kształtowaniu zmienności pokrywy lodowej staje się nikła. Po dalszych kilku latach utrzymywania się reżimu „chłodnego” międzyroczne zmiany powierzchni zlodzonej stają się małe. Analizy związków między zmiennymi z przesunięciami czasowymi wykazały, że cyrkulacja atmosferyczna nad Arktyką stanowi funkcję THC. W rezultacie, za główną przyczynę zmian powierzchni zlodzonej Arktyki należy uznać rozciągnięte w czasie działanie zmian intensywności THC, które w rozpatrywanym okresie objaśnia ~90% wariancji rocznej powierzchni zlodzonej.
    The paper presents the assumptions and structure of statistical model reproducing the changes in sea ice extent in the Arctic, using the minimum number of steering variables. The data set of NASA's Goddard Space Flight Center (GSFC) nsidc0192_seaice_trends_climo/total-area-ice-extent/nasateam/ (Total Ice-Covered Area and Extent) was used as starting data in the calibration of this model. Its subsets characterizing the sea ice extent of the Arctic Ocean (ArctOcn), Greenland Sea (Grnland), Barents and Kara seas (BarKara) were used. Their sums create a new variable known as the ‘Proper Arctic’. This model also used the following subsets: Archipelago Canadian (CanArch), Bay and Strait Hudson (Hudson), and Baffin Bay and Labrador Sea (Baffin), the sum of which creates another variable the ‘American Arctic’. The sum of all the above mentioned subsets creates a variable defined as the ‘entire Arctic’. The study covered the period 1979-2013, for which the said data set is made up of uniform and reliable data based on satellite observations. The model was developed for moments of maximum (March) and minimum (September) development of sea ice extent as well as for the annual average sea ice extent. After presenting the assumptions of the model (model type ‘White box’), formal analysis of the type and characteristics of the model, the choice of steering variables (independent; Chapters 3 and 4) was made. The index characterizing the intensity of thermohaline circulation (THC) in the North Atlantic, referred to as DG3L and an index characterizing atmospheric circulation having significant influence on changes in sea ice extent, marked as D, were used as independent variables in this model. Physical fundamentals and rules for calculating the DG3L index are discussed in detail in Annex 1, and the D index in Annex 2. These Annexes also include time series of both indexes (DG3L – 1880-2015; D – 1949-2015). Research into delays between the impact of variables and changes in sea ice extent indicated that sea ice extent showed maximum strength of the correlation with the DG3L variable with a three-year delay and with D variable with zero delay. The final form of the model is a simple equation of multiple regression (equation [1]). The following equations are used for estimating the regression parameters for individual sea areas in those time series: the Proper Arctic – equation [1a, 1b, 1c]; the American Arctic – equations [2a, 2b, 2c] and for the entire Arctic - equation [3a, 3b, 3c]. Statistical characteristics of each model are presented in Tables 3, 4 and 5, and Figures 2, 3 and 4 respectively and show the scattering of values estimated by means of each model in relation to the observed values. All models show high statistical significance. The best results, both in terms of explanation of the variance of the observed sea ice extent, as well as the size of the standard errors of estimation of sea ice extent are obtained for changes in the sea ice extent of the entire Arctic. The reasons for this may be traced back to the fact that errors in the estimation of partial models ([1a, 1b, 1c] and [2a, 2b, 2c]) have different signs, which in a synthetic model partially cancel out each other. Moreover, if the variable DG3L three years before shows strong and evenly distributed in time action, the D variable characterizing atmospheric circulation shows clearly seasonal activity – it is marked only during the minimum development of sea ice extent (September), when the degree of ice concentration is reduced, allowing its relatively free drift. The model for the annual average of sea ice extent of the entire Arctic (in the accepted limits) explains 71.5% of the variance, in September 68%, and in March 65% of the variance (Table 5). The lowest values are obtained for the American Arctic, where the D variable, characterizing atmospheric circulation does not appear to have significant influence, so the model is a linear equation with one variable (DG3L). Nevertheless, also in this case, the variance of the annual sea ice extent in the American Arctic is explained exceeding 50%. Variability of THC (described by the DG3L index) explains ~67% of the variance of annual sea ice extent and variability of atmospheric circulation (described by the D index) explains ~6% of the variance of annual sea ice extent of the entire Arctic. It allows claiming that THC and atmospheric circulation are the essential factors that influence the variability of sea ice extent of the Arctic. Both of these factors are natural factors. Further analysis of the results presented by various models and especially those affected by the DG3L variable (Fig. 5) delayed by three years suggests that the linear model is not the most appropriate model reflecting the changes in the sea ice extent of the entire Arctic and its parts. The action of DG3L variable, accumulated over several years, is saved and this causes that a strong significant correlation with the sea ice extent is prolonged. The analysis carried out by means of the segmented regression showed that the variability of sea ice extent was different where THC is lower than the average (DG3L ≤ 0), or different where THC is stronger than average (DG3L> 0; see equation [4a, 4b]). When the index is zero or less than zero, the impact of THC on the increase in sea ice extent is limited and the influence of changes in atmospheric circulation on sea ice extent is very small. Conversely, when the THC becomes intense and imports increased amounts of heat to the Arctic, the influence of DG3L index on the decrease in sea ice extent rises, like growing impact of atmospheric circulation on variation of sea ice extent (see equations [5a, 5b]. The segmented regression equations with these two variables explain 88.76% of the observed annual variation of sea ice extent of the entire Arctic (equations [5a, 5b]).This means that the sea ice extent of the Arctic is variable in two distinct regimes – ‘warm’, when the DG3L> 0 and ‘cold’, when the DG3L ≤ 0. This is similar to the results of Proshutinsky and Johnson (1997), Polyakov et al. (1999) and Polyakov and Johnson (2000) and their LFO oscillation. Time limits of the transition intensity of the THC phases from the positive to negative and vice versa correspond to similar limits of LFO, suggesting that the two different systems have the same cause. Polyakov and Johnson (2000) and Polyakov et al. (2002, 2003, 2004, 2005) can see the main reason for the change in the LFO regime in the transition of atmospheric circulation from anticyclonic regime to cyclonic regime and vice versa. The analysis of the reason for the transition of regime of changes in sea ice extent from ‘warm’ to ‘cold’ and vice versa – THC or atmospheric circulation – has shown that the D index is a function of previous changes in DG3L index. Atmospheric circulation over the Arctic shows a greater delay in response to changes in THC than the sea ice extent – this occurs with a 6-year delay (see Table 6, Equation 6). This allows replacing the D variable in the equations describing the change in sea ice extent, directly by DG3L variable from 6 years before (see Equation [7a, 7b]).These simultaneous equations explain about 90% of the observed annual variance of the sea ice extent of the entire Arctic in the years 1979-2013. Most importantly, however, it can be stated, with a high degree of certainty, that the variability of THC of the North Atlantic steers both the changes in sea ice extent and Basic features of atmospheric circulation over the Arctic. The effects of other factors than THC, having influence on variability of sea ice extent and the basic processes of the climate in the Arctic, in the short time scales, leave not too much space/place. The transition from ‘cold’ to ‘warm’ regime in the development of the sea ice extent in the Arctic requires an increase in the intensity of THC. If the values of DG3L index are greater than 0 for a period not shorter than three years, the decrease in the sea ice extent will start, initially in the period of its minimum development (August, September). If the resultant values of the DG3L index have positive values for further three years, the atmospheric circulation will transform into a cyclonic circulation (D index goes to positive values). The role of atmospheric circulation during the ‘warm’ season in the Arctic having influence on the change (reduction) of the sea ice extent becomes significant. The ‘warm’ regime will remain as long as long after its start the situation in which the algebraic sum of DG3L values is greater than 0. If such a situation lasts long, or in case of accumulation of high values of DG3L index, the sea ice cover can disappear almost completely in the warm period. The transition from the ‘warm’ regime to the ‘cold’ regime demands fulfillment of reverse conditions – a consistent decrease in the values of DG3L index into negative values for at least another three year period. After three years this will result in rapid increase in sea ice extent during warm period, thereby increasing the annual average of sea ice extent. If in subsequent years the value of DG3L index remains lower than zero, after the next 3-4 years, the atmospheric circulation will become the anticyclonic circulation. After that there will be gradual, slow growth in sea ice extent, decrease in air temperature, increase in ice thickness and change in the age of the ice structure towards the increase in the multi-year ice. The ice cover in the Arctic will become "self-sustaining", reducing interannual variability. Major changes will occur in the ‘warm’ season, minor in other seasons. The maximum sea ice extent of the Arctic in the cold season, with current conditions in the ‘cold’ regime, can reach ~13.5-14.5 million km2, the average annual sea ice extent should be ~12 (± 0.5) million km2. This area, especially in the winter season, may be in fact higher, since the weakening of the THC must also lead to a decrease in air temperature in the hemisphere.
    Źródło:
    Problemy Klimatologii Polarnej; 2015, 25; s. 249-334
    1234-0715
    Pojawia się w:
    Problemy Klimatologii Polarnej
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-15 z 15

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