Increased reservoir ages and poorly ventilated deep waters inferred in the glacial Eastern Equatorial Pacific.

Consistent evidence for a poorly ventilated deep Pacific Ocean that could have released its radiocarbon-depleted carbon stock to the atmosphere during the last deglaciation has long been sought. Such evidence remains lacking, in part due to a paucity of surface reservoir age reconstructions required for accurate deep-ocean ventilation age estimates. Here we combine new radiocarbon data from the Eastern Equatorial Pacific (EEP) with chronostratigraphic calendar age constraints to estimate shallow sub-surface reservoir age variability, and thus provide estimates of deep-ocean ventilation ages. Both shallow- and deep-water ventilation ages drop across the last deglaciation, consistent with similar reconstructions from the South Pacific and Southern Ocean. The observed regional fingerprint linking the Southern Ocean and the EEP is consistent with a dominant southern source for EEP thermocline waters and suggests relatively invariant ocean interior transport pathways but significantly reduced air-sea gas exchange in the glacial southern high latitudes

Identification and removal of Mn-Mg-rich contaminant phases in foraminiferal tests: Implications for Mg/Ca past temperature reconstructions

The geochemical composition of foraminifera shells from an Ocean Drilling Program site in the Panama Basin has been analyzed by several analytical techniques (LA-ICP-MS, ICP-MS, XRD, SEM, EDX) in order to identify and evaluate the occurrence of contaminant phases which may bias paleoenvironmental reconstructions. LA-ICP-MS results on uncleaned tests indicate the presence of Mn-Mg-rich contaminant phases at the inner surfaces of the foraminiferal shells (which have Mn/Ca ratios up to 400 mmol mol-1 and Mg/Ca ratios up to 50 mmol mol-1). We have rigorously assessed the ability of different cleaning protocols to remove these contaminant phases and have obtained satisfactory results only when a reductive step is included. The analysis of cleaning residuals collected after each of the different cleaning steps applied reveals that high Mn values are associated with at least two different contaminant phases, of which only one is linked to high Mg values. XRD analysis further reveals that the Mn-Mg-rich phase is the Ca-Mn-Mg carbonate kutnahorite (Ca(Mn, Mg)(CO3)2). Our results demonstrate that the presence of kutnahorite-like minerals can bias Mg/Ca ratios toward higher values (by 7-36%) and lead to significant overestimation of past seawater temperatures (by 0.9 up to 6.2°C, in the case of these Panama Basin samples)

The Evolution of Deep Ocean Chemistry and Respired Carbon in the Eastern Equatorial Pacific Over the Last Deglaciation

It has been shown that the deep Eastern Equatorial Pacific (EEP) region was poorly ventilated during the Last Glacial Maximum (LGM) relative to Holocene values. This finding suggests a more efficient biological pump, which indirectly supports the idea of increased carbon storage in the deep ocean contributing to lower atmospheric CO2 during the last glacial. However, proxies related to respired carbon are needed in order to directly test this proposition. Here we present Cibicides wuellerstorfi B/Ca ratios from Ocean Drilling Program Site 1240 measured by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) as a proxy for deep water carbonate saturation state ([CO32-], and therefore [CO32-]), along with C-13 measurements. In addition, the U/Ca ratio in foraminiferal coatings has been analyzed as an indicator of oxygenation changes. Our results show lower [CO32-], C-13, and [O-2] values during the LGM, which would be consistent with higher respired carbon levels in the deep EEP driven, at least in part, by reduced deep water ventilation. However, the difference between LGM and Holocene [CO32-] observed at our site is relatively small, in accordance with other records from across the Pacific, suggesting that a counteracting mechanism, such as seafloor carbonate dissolution, also played a role. If so, this mechanism would have increased average ocean alkalinity, allowing even more atmospheric CO2 to be sequestered by the ocean. Therefore, the deep Pacific Ocean very likely stored a significant amount of atmospheric CO2 during the LGM, specifically due to a more efficient biological carbon pump and also an increase in average ocean alkalinity

Atmosphere-ocean linkages in the eastern equatorial Pacific over the early Pleistocene

Here we present a new set of high-resolution early Pleistocene records from the eastern equatorial Pacific (EEP). Sediment composition from Ocean Drilling Program Sites 1240 and 1238 is used to reconstruct past changes in the atmosphere-ocean system. Particularly remarkable is the presence of laminated diatom oozes (LDOs) during glacial periods between 1.85 and 2.25Ma coinciding with high fluxes of opal and total organic carbon. Relatively low lithic particles (coarse and poorly sorted) and iron fluxes during these glacial periods indicate that the increased diatom productivity did not result from dust-stimulated fertilization events. We argue that glacial fertilization occurred through the advection of nutrient-rich waters from the Southern Ocean. In contrast, glacial periods after 1.85Ma are characterized by enhanced dust transport of finer lithic particles acting as a new source of nutrients in the EEP. The benthic ecosystem shows dissimilar responses to the high productivity recorded during glacial periods before and after 1.85Ma, which suggests that the transport processes delivering organic matter to the deep sea also changed. Different depositional processes are interpreted to be the result of two distinct glacial positions of the Intertropical Convergence Zone (ITCZ). Before 1.85Ma, the ITCZ was above the equator, with weak local winds and enhanced wet deposition of dust. After 1.85Ma, the glacial ITCZ was displaced northward, thus bringing stronger winds and stimulating upwelling in the EEP. The glacial period at 1.65Ma with the most intense LDOs supports a rapid southward migration of the ITCZ comparable to those glacial periods before 1.85Ma

Identification and removal of Mn-Mg-rich contaminant phases in foraminiferal tests: Implications for Mg/Ca past temperature reconstructions

The geochemical composition of foraminifera shells from an Ocean Drilling Program site in the Panama Basin has been analyzed by several analytical techniques (LA-ICP-MS, ICP-MS, XRD, SEM, EDX) in order to identify and evaluate the occurrence of contaminant phases which may bias paleoenvironmental reconstructions. LA-ICP-MS results on uncleaned tests indicate the presence of Mn-Mg-rich contaminant phases at the inner surfaces of the foraminiferal shells (which have Mn/Ca ratios up to 400 mmol mol-1 and Mg/Ca ratios up to 50 mmol mol-1). We have rigorously assessed the ability of different cleaning protocols to remove these contaminant phases and have obtained satisfactory results only when a reductive step is included. The analysis of cleaning residuals collected after each of the different cleaning steps applied reveals that high Mn values are associated with at least two different contaminant phases, of which only one is linked to high Mg values. XRD analysis further reveals that the Mn-Mg-rich phase is the Ca-Mn-Mg carbonate kutnahorite (Ca(Mn, Mg)(CO3)2). Our results demonstrate that the presence of kutnahorite-like minerals can bias Mg/Ca ratios toward higher values (by 7-36%) and lead to significant overestimation of past seawater temperatures (by 0.9 up to 6.2°C, in the case of these Panama Basin samples)

A Production of the Novel "Comrade Kislyakov" by P. Romanov on the Stage of the Riga Theatre of Russian Drama.

Maģistra darbs „P.Romanova romāna "Biedrs Kisļakovs" inscenējums uz Rīgas Krievu Drāmas teātra skatuves” tiek veltīts literāra darba inscenējuma fenomenam, kas sākotnēji nebija paredzēts iestudējumam uz teatrālas skatuves. Maģistra darbā ir apskatīti episka, dramatiska un teatrāla darba īpatnības, ka arī jēdziens „inscenējums”. Balstoties uz romanu P.Romanova "Biedrs Kisljakovs” un R.Ungerna lugas „Trīs pāri zīda zeķes” ir atklāti sacerējuma prozas inscenējuma veidi un metodes, kas ļāva redzēt inscenējuma transformāciju patstāvīgā daiļdarbā.The Master's research paper “A Production of the Novel Comrade Kislyakov by P. Romanov on the Stage of the Riga Theatre of Russian Drama” is dedicated to the phenomenon of dramatisation of the literary work which originally was not designed to the staging. In the present research paper the special features of theater, epic and dramatic literary works as well as the concept of “staging” are examined in detail. On the material of the novel "Comrade Kislyakov" by Panteleimon Romanov and Rudolf Ungern's play 'Three pairs of silk stockings” the means and ways of dramatisation of a narrative literary work are singled out; this allowed to see the transformation of the dramatisation into an independent work of fiction