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Czynniki zmian klimatycznych w środkowym i górnym plejstocenie : ich zapis geologiczny w osadach Oceanu Południowego oraz rdzeniach lodowych

Kotrys B.

Przegląd Geologiczny

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2016

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Vol. 64, nr 1

35--42

EN

Climate changes during the Pleistocene were driven by large-scale orbital perturbations as well as by internal feedbacks on the Earth. One of the main roles in climate modelling is played by the Southern Ocean that is a great source of sea ice, carbon dioxide, dissolved silica and nutrients. Numerous sediment and ice records derived from the Southern Ocean and Antarctica document high-resolution climatic changes that allow us a better understanding of global climate evolution. Consistently with the global climatic trend, several sea surface temperature (SST) records of the Southern Ocean are marked by a distinct shift from low to high glacial/interglacial variability around Termination V (T V), called the Mid-Brunhes Event (MBE). Prior to T V, the Southern Ocean’s SST displays lower values and low variability. It points to a distinct expansion of the Southern Ocean cold water masses and positional changes of hydrographical fronts during most of the lower Middle Pleistocene, which started in the Pliocene. Beside large climatic changes, several abrupt distinct warming and cooling phases have been recognized. Some of them (MIS 22–19, MIS 11 and MIS 5) show similarities to MIS 1, which could be used for future climate predictions. In this paper we would like to present the middle and late Pleistocene climatic mechanisms in the Southern Ocean, and to show SST changes in relation to the hydrographic frontal movement, sea ice development and CO2 oscillations.

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Rekonstrukcje paleotemperatur w strefie Frontu Polarnego Oceanu Południowego (sektor atlantycki) na podstawie środkowo-górnoplejstoceńskich promienic z odwiertu ODP Leg 177 Site 1091

Kotrys B.

Przegląd Geologiczny

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2014

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Vol. 62, nr 9

448--455

EN

Quantitative analysis of radiolarian assemblages, carried out at the Ocean Drilling Program (ODP) Leg 177 Site 1091 (Atlantic sector of the Southern Ocean), provides a well-established summer sea surface temperature (SSST) record from the Polar Front Zone extending back into the Middle Pleistocene at orbital- -submillennial resolution. In order to estimate the SSST, the Imbrie & Kipp method (IKM) and the artificial neural network (ANN) were applied. The SSST records derived from the IKM and ANN display close similarities in paleotemperature fluctuations, amplitudes and absolute values. The ANN-derived SSST estimations display a pattern of slightly more distinct warm events that is closest to the records obtained from EDC (EPICA Dome C) ice cores and ODP Site 1090. The warm events indicate a distinct shift in the extent of the Southern Ocean cold water sphere that must have affected the ocean–atmosphere–ice field interactions and the configuration of high-latitude wind fields. Consistently with the global trend of paleotemperature fluctuation, the SSST record is marked by a distinct shift from low to high glacial/interglacial variability around Termination V. Prior to Termination V, the SSST displays coldest values and low variability. It points to a distinct expansion of the Southern Ocean cold water masses and positional changes of hydrographical fronts during most of the lower Middle Pleistocene.

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Tracing the signature of various frontal systems in stable isotopes (oxygen and carbon) of the planktonic foraminiferal species Globigerina bulloides in the Southern Ocean (Indian Sector)

Khare N., Chaturvedi S. K.

Oceanologia

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2012

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No. 54 (2)

311-323

EN

Twenty-five surficial sediment samples, collected on board ORV Sagar Kanya during her 199th and 200th cruises along a north-south transect between latitudes 9.69°N and 55.01°S, and longitudes 80°E and 40°E were studied for isotopic variations (values of δ18^O and δ^13C) of the indicator planktonic species Globigerina bulloides. The results indicate that from latitudes 9.69°N to 15°S both these isotopes (δ^18 O and δ^13C) fluctuated significantly. Between latitudes from around 15°S to 30-35°S δ18^ O values steadily increased, whereas δ^13C showed a decreasing trend. However, to the south of latitudes 30-35°S, both isotope values showed a similar response with a gradual increase up to latitude 50°S, beyond which δ^18 O continued to increase while δ^13C declined. The characteristic patterns of the values of both isotopes indicates that the signatures of different water masses are associated with various frontal systems and/or water masses across the transect. The signature of the Polar Front at around latitude 50°S shows the specific response of the isotopic values (δ^18 O and δ^13C) of G. bulloides. Such a response beyond 50°S latitude is ascribable to the general decrease in the ambient temperature, resulting in a continuous increase in δ^18 O values, while δ^13C values decrease as a result of reduced photosynthesis in regions approaching higher latitudes owing to low light penetration. To further corroborate our results, those of many such transects from geographically distinct regions need to be studied for isotopic variations in the calcareous shells of planktonic foraminiferal species. The results have the potential to be used as a proxy to assess the movement of frontal systems in southern high latitude regions.

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Trendy temperatury powierzchni oceanu w sektorze pacyficznym Oceanu Południowego w ostatnim 25-leciu

Marsz A. A.

Problemy Klimatologii Polarnej

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2005

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nr 15

17-26

PL

Praca omawia zmiany temperatury powierzchni wody (TPO) sektora pacyficznego Oceanu Południowego w pasach szerokości 60 i 50°S, zachodzące w przekrojach miesięcznych i rocznych. Stwierdzono występowanie ujemnych trendów TPO w całym pasie 60°S, z czego ponad 1/3 współczynników trendu jest istotna i wysoce istotna statystycznie. Obszary silnego ochłodzenia powierzchni oceanu tworzą tam dwa ośrodki: pierwszy w rejonie 170°E - 140°W, drugi - 120-080°W. W obu ośrodkach najsilniejsze spadki TPO następują w miesiącach chłodnej pory roku (maj - sierpień), w drugim - dodatkowo - stosunkowo silne ochłodzenie zaznacza się w miesiącach ciepłej pory roku (styczeń - marzec). Na szerokości 50°S ochłodzenie jest znacznie słabsze - istotne statystycznie zmiany TPO zaznaczają się wyłącznie po wschodniej stronie sektora (100-080°W), gdzie również występują trendy ujemne. Kumulacja istotnych i nieistotnych statystycznie trendów miesięcznych prowadzi do zaznaczania się na obszarze około 54% powierzchni sektora pacyficznego Oceanu Południowego istotnych statystycznie, ujemnych trendów rocznej TPO. Na pozostałym obszarze badanego sektora bądź brak realnych zmian TPO, bądź występuje tendencja do słabego spadku temperatury. Przebiegi temperatury rocznej wskazują, że w ośrodku zachodnim (60°S, 170°E -140°W) TPO konsekwentnie obniża się od początku obserwacji (1980 rok), gdy we wschodniej części sektora pacy-ficznego (120-080°W) cały obserwowany w 25-leciu trend stanowi konsekwencję silnego spadku rocznej TPO w ciągu ostatnich 7 lat (1997-2004).

EN

This work deals with monthly and annual changes in sea surface temperature (SST) of the Pacific sector of the South Ocean observed in 60°- 50°S latitudinal bands. The occurrence of negative trends of SST was noted in the entire 60° band and 1/3 of the trend coefficients is statistically significant and highly significant. The regions marked by strong cooling of ocean surface are formed by two centres - one 170° - 140°W and the other extending from 120° to 080°W. The greatest decrease in sea surface temperature in both centres takes place during cold season (May - August), in the other centre there is also additional quite strong cooling in the months of warm season (January - March). In the latitude 50°S the cooling is much weaker - statistically significant changes in SST are observed only in the eastern part of the Pacific region (100°- 080°W) where negative trends are also noted. Cumulating of statistically significant and non-significant monthly trends leads to statistically significant negative trends in annual SST observed in 54% of the area in the Pacific sector of the South Ocean. In the remaining area of the Pacific sector of the South Ocean there are either no visible changes in the sea surface temperature or there is tendency of weak decrease in temperature. The courses of annual SST indicate that in the western region (60S°, 170° -140°W) the SST has been decreasing constantly since the beginning of the observational period (since the year 1980), whereas in the eastern part of the Pacific sector (120°- 080°W) the whole trend observed over the 25-year period results from strong decrease in annual SST in the period of last 7 years (1997-2004).