Department of Geographyhttps://dspace.mic.ul.ie/handle/10395/282024-03-29T09:11:28Z2024-03-29T09:11:28ZMediterranean sea surface temperatures and planktonic foraminifera palaeoecology during short-term climate oscillations of the Late Pleistocenehttps://dspace.mic.ul.ie/handle/10395/30312022-03-31T02:00:42Z2022-03-30T00:00:00ZMediterranean sea surface temperatures and planktonic foraminifera palaeoecology during short-term climate oscillations of the Late Pleistocene
The Mediterranean is a semi-enclosed sea, ideally located for recording and amplifying global climate signals. Heinrich Stadial 1 (HS1), the Bølling-Allerød (BA) and Younger Dryas (YD) are periods of extreme climatic change that occurred during the last deglacial. Planktonic foraminifera were utilised to address the extent the Mediterranean Sea responded to these events, and how they impacted sea surface temperatures (SSTs), hydrology and distribution of planktonic foraminifera on a basin-wide scale. This was further expanded upon in the Gulf of Lion, in order to determine the palaeoenvironmental impacts and main drivers in this region during the deglacial.
A database of planktonic foraminiferal counts from 67 cores located across the Mediterranean Sea were compiled. SSTs were reconstructed using Artificial Neural Networks (ANN) and mapped for each chronozone, along with key planktonic foraminifera and palaeoenvironmental proxies. Mean annual SSTs ranged from 13.57°C and 14.19°C during HS1 and the YD, both cooler than the Last Glacial Maximum (LGM). SSTs during the BA increased to 15.03°C. The western basin, Adriatic and Aegean Seas remained cool and strongly eutrophic, dominated by Neogloboquadrina species, G. bulloides, T. quinqueloba and G. inflata since the BA. The eastern basin was more productive than today, with a mix of eutrophic species and G. ruber plexus, though it became increasingly seasonal, oligotrophic and stratified as SSTs warmed during the BA and YD. These reconstructions highlight the complexity of these chronozones across the Mediterranean Sea. They also illustrated how global drivers such as the southerly position of the polar front, North Atlantic atmospheric circulation, precipitation and wind strength, sea level, summer insolation and position of the ITCZ governed these signals. River discharge and meltwater pulses were regionally important along northern margins.
Analysis of the high-resolution Gulf of Lion core M40/4 82-2SL focused the late HS1 to mid Holocene (~15.5 to 7.4 kyr). SSTs were predicted using ANN, and a combination of faunal abundance, multivariate statistics (PCA) and palaeoenvironmental proxies were utilised to reconstruct the palaeoenvironment. Predicted SSTs showed strong correlation with Greenland δ18O ice cores, especially during the BA (15.19°C). SSTs during the late HS1 (10.18°C) and YD (8.3°C) were cooler than the LGM. The assemblage was strongly eutrophic throughout, with a more diverse, seasonal assemblage restricted to the early Bølling and Holocene. Holocene SSTs were cooler than expected (15.06 to 15.76°C), as the early Holocene was overprinted by a strong cyclical river/meltwater signal. This freshening of surface waters impacted the depth of the pycnocline, which had significant impacts on N. incompta. Variations in wind-strength, precipitation, river discharge and Alpine meltwaters were the main factors governing the Gulf of Lion during the Late Pleistocene to mid Holocene transition.
2022-03-30T00:00:00ZA palaeoecological analysis of late quaternary sapropels from the Mediterranean Ridgehttps://dspace.mic.ul.ie/handle/10395/29282020-12-19T03:00:43Z2020-12-18T00:00:00ZA palaeoecological analysis of late quaternary sapropels from the Mediterranean Ridge
A PALAEOECOLOGICAL ANALYSIS OF LATE QUATERNARY SAPROPELS FROM THE MEDITERRANEAN RIDGE
By Darren Barry
The sedimentary sequences of the Eastern Mediterranean Sea are interspersed by blackcoloured, organic rich deposits called sapropels. Ranging in thickness from a few millimeters to as much as tens of centimetres these sedimentary layers have been deposited throughout the late Cenozoic. Despite intensive research the exact environmental conditions that led to the deposition of these sapropels are not yet fully understood. Using planktonic foraminifera as a proxy, this research focuses on the deposition of several sapropels. In addition to the more commonly studied sapropels (S1 and S5) S3 and S6 have also been investigated. The principle aim of this research is to reconstruct the palaeoenvironmental conditions during these depositional events. In addition to using the traditional method of analysing faunal assemblages, particular emphasis will be placed on accessing the test size variation of individual species of planktonic foraminifera. This technique has been applied to other events in Earth’s history but not in relation to sapropel deposition.
The research is based on data extracted from ODP core 969A (latitude 33.84N, longitude 24.88E, water depth 2200.3 m). With the exception of S1 (7cm), the thickness of each sapropel (S3 – 28cm; S5 – 28cm; S6 – 41cm) allows each event to be analysed at a sufficiently high resolution. One aspect of this study related to the palaeoenvironmental reconstruction of two cores from open ocean sites. Using micropalaeontological data along with multivariate statistical analysis has allowed detailed analysis of palaeoenvironmental variability since the Last Glacial Maximum (LGM). In addition, estimates of sea surface temperature (SST) shows a gradual climate amelioration from the LGM to present. A unique aspect of this research examined the mean test size data of two shallow and one deep dwelling planktonic foraminiferal species over two sapropel events. Particular attention was paid to both biotic and abiotic factors in the understanding of their effects on species growth. While no obvious increase in mean test size was noted as a direct response to sapropel deposition, variability throughout these timeframes is observed. It is concluded that the mean test size of each species responds differently depending on their SST and nutrient requirements. For the Eemian interglacial sapropel S5 and glacial sapropel S6, a palaeoecological analysis utilising palaeoenvironmental indices reconstructed the water column dynamics and trophic status during these depositional events. Sapropel S5 exhibited considerable variability in response to the position of the Cretan gyre while a two phase depositional event in S6 indicated extreme shoaling of the pycnocline.
2020-12-18T00:00:00ZIN-SIGHT EPA/ERTDI Project # 2002-W-LS/7 Work Package (WP) 3 (months 21-36)https://dspace.mic.ul.ie/handle/10395/27472019-03-21T03:01:21Z2006-01-01T00:00:00ZIN-SIGHT EPA/ERTDI Project # 2002-W-LS/7 Work Package (WP) 3 (months 21-36)
IN-SIGHT EPA/ERTDI Project # 2002-W-LS/7 Work Package (WP) 3 (months 21-36).
2006-01-01T00:00:00ZLocal partnerships in local governance: the sub-regional dimension of devolutionhttps://dspace.mic.ul.ie/handle/10395/24422019-01-29T15:06:56Z1999-01-01T00:00:00ZLocal partnerships in local governance: the sub-regional dimension of devolution
Local partnerships in local governance: the sub-regional dimension of devolution
1999-01-01T00:00:00Z