scholarly journals Carbon isotopic equilibrium of the surface waters as a proxy for climate change through the last glacial/interglacial cycle in the Southwest Pacific

2021 ◽  
Author(s):  
◽  
Charles Reynolds Maxson
Keyword(s):  
New Zealand ◽  
Ocean Circulation ◽  
Potential Temperature ◽  
World Ocean ◽  
The Holocene ◽  
Southwest Pacific ◽  
Carbon Isotopic ◽  
Modern Distribution ◽  
Stable Conditions ◽  
Geochemical Property

<p>Carbon-13 is a relatively understudied geochemical property in the world ocean. The Southwest Pacific, in particular, is devoid of δ¹³C data. This thesis therefore has two main objectives: to create a model to describe the modern distribution of δ¹³C around New Zealand (30-70°S, 140°E-150°W), and to describe changes in δ¹³C in a latitudinal transect of cores to the east and south of New Zealand. A model using multiple linear regression was created by comparing δ¹³C with potential temperature, salinity, density, and oxygen data. This model matches well with ship board δ¹³C measurements taken throughout the region. The resulting models were then compared to core top data to determine how well modern δ¹³C values compare to the Holocene, pre-industrial values. A new model, based on previous pre-industrial models, was created at much higher resolution to recreate the pre-industrial δ¹³C distribution. Core top values were found to be intermediate between Holocene and modern values. Down core δ¹³C data was split into six regions based on oceanographic conditions to determine what caused and how δ¹³C change occurred in the past. Data was run through 1000 iterations of a Monte Carlo simulation to determine a robust δ¹³C curve back through time. The biologic pump was found to dominate the δ¹³C levels in the region through iron fertilization and increased productivity in the polar zone. The LGM and deglacial δ¹³C values reflect greater influence on δ¹³Catm, suggesting that an increase in upwelling along the Antarctic coast and a possible strengthening of the westerly wind belt caused changes in ocean circulation throughout the region. The ACR and Early Holocene periods show good correlation with atmospheric CO₂ records, suggesting increasing temperatures may have increased productivity. The remainder of the Holocene to the present is mainly influenced by δ¹³Catm, suggesting relatively stable conditions in ocean and atmosphere.</p>

scholarly journals Carbon isotopic equilibrium of the surface waters as a proxy for climate change through the last glacial/interglacial cycle in the Southwest Pacific

2021 ◽  
Author(s):  
◽  
Charles Reynolds Maxson
Keyword(s):  
New Zealand ◽  
Ocean Circulation ◽  
Potential Temperature ◽  
World Ocean ◽  
The Holocene ◽  
Southwest Pacific ◽  
Carbon Isotopic ◽  
Modern Distribution ◽  
Stable Conditions ◽  
Geochemical Property

<p>Carbon-13 is a relatively understudied geochemical property in the world ocean. The Southwest Pacific, in particular, is devoid of δ¹³C data. This thesis therefore has two main objectives: to create a model to describe the modern distribution of δ¹³C around New Zealand (30-70°S, 140°E-150°W), and to describe changes in δ¹³C in a latitudinal transect of cores to the east and south of New Zealand. A model using multiple linear regression was created by comparing δ¹³C with potential temperature, salinity, density, and oxygen data. This model matches well with ship board δ¹³C measurements taken throughout the region. The resulting models were then compared to core top data to determine how well modern δ¹³C values compare to the Holocene, pre-industrial values. A new model, based on previous pre-industrial models, was created at much higher resolution to recreate the pre-industrial δ¹³C distribution. Core top values were found to be intermediate between Holocene and modern values. Down core δ¹³C data was split into six regions based on oceanographic conditions to determine what caused and how δ¹³C change occurred in the past. Data was run through 1000 iterations of a Monte Carlo simulation to determine a robust δ¹³C curve back through time. The biologic pump was found to dominate the δ¹³C levels in the region through iron fertilization and increased productivity in the polar zone. The LGM and deglacial δ¹³C values reflect greater influence on δ¹³Catm, suggesting that an increase in upwelling along the Antarctic coast and a possible strengthening of the westerly wind belt caused changes in ocean circulation throughout the region. The ACR and Early Holocene periods show good correlation with atmospheric CO₂ records, suggesting increasing temperatures may have increased productivity. The remainder of the Holocene to the present is mainly influenced by δ¹³Catm, suggesting relatively stable conditions in ocean and atmosphere.</p>

scholarly journals Assessment of the representation of Antarctic Bottom Water properties in the ECCO2 reanalysis

Ocean Science ◽  
2014 ◽  
Vol 10 (6) ◽  
pp. 923-946 ◽  
Author(s):  
M. Azaneu ◽  
R. Kerr ◽  
M. M. Mata
Keyword(s):  
Southern Ocean ◽  
Ocean Circulation ◽  
Bottom Water ◽  
Potential Temperature ◽  
World Ocean ◽  
Volume Transport ◽  
Weddell Sea ◽  
Antarctic Bottom Water ◽  
Water Properties ◽  
The Absolute

Abstract. We analyzed the ability of the Estimating the Circulation and Climate of the Ocean – Phase II (ECCO2) reanalysis to represent the hydrographic properties and variability of Antarctic Bottom Water (AABW) in the Southern Ocean. We used a 20-year (1992–2011) observational database to perform comparisons of hydrographic properties and reanalysis output for the same time period. Four case studies based on current meter data and the AABW volume transport estimates previously reported in the literature were also evaluated. The opening and maintenance of an oceanic polynya in the Weddell Sea sector is observed after 2004 in the reanalysis product. Moreover, intense deep water production due to deep convection occurs, which leads to a scenario in which the Weddell Sea is flooded with AABW. For this reason, our analyses focused on the period that was identified as more reliable (1992–2004). The main Southern Ocean oceanographic features, as well as the characteristic shape of the regional potential temperature–salinity (θ–S) diagrams, are coincident with observations. However, the reanalysis output produces surface waters that are generally denser than observations due to the reproduction of waters that are generally saltier than expected, which probably resulted from the strong seasonality of sea ice concentrations. Bottom waters are warmer and less dense, while intermediate waters are statistically closest to the observations. The differences in bottom water properties are partially due to the inability of the reanalysis to properly reproduce the formation and export of dense waters from the shelf and the consequent absence of the densest AABW variety for most of the analyzed period. Despite differences in the absolute values, the upper AABW limit (γn ≥ 28.27 kg m−3) and AABW occupied area estimates are coincident with the observations in the World Ocean Circulation Experiment (WOCE) repeat sections SR2 and SR4. Moreover, the AABW volume export and current velocity variability are correlated with the observed time series in the most important region of dense water export (i.e., the Weddell Sea). Despite the consistency in terms of variability, the absolute volume transport and velocity estimates are underrepresented in all cases.

scholarly journals Structure and Causes of the Pulsation Mode in the Antarctic Circumpolar Current South of Australia

2011 ◽  
Vol 41 (2) ◽  
pp. 253-268 ◽  
Author(s):  
C. O. Dufour ◽  
J. Le Sommer ◽  
T. Penduff ◽  
B. Barnier ◽  
M. H. England
Keyword(s):  
Ocean Circulation ◽  
Potential Temperature ◽  
World Ocean ◽  
Physical Space ◽  
Intermediate Water ◽  
Mode Water ◽  
Pulsation Mode ◽  
Southeast Indian Ridge ◽  
Circumpolar Current ◽  
The Impact

Abstract The subsurface variability of potential temperature and salinity south of Australia along 130°E is studied over a 25-yr period (1980–2004). The study is done with fields provided by a global eddy-permitting model of the DRAKKAR project forced by atmospheric reanalysis. The analysis performed by C. Sun and D. R. Watts with in situ hydrographic data is repeated. Sun and Watts have investigated the EOF modes in streamfunction space along the World Ocean Circulation Experiment (WOCE) SR3 section. In particular, they found that an EOF mode, which they called the “pulsation mode,” strongly dominates subsurface thermohaline variations. Here, it is found that, in the model, an EOF mode with spatial structure similar to the Sun and Watts pulsation mode dominates subsurface thermohaline variations in streamfunction space. The mode displays a maximum of variability at the Subantarctic Front (SAF) between Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW). The associated time series exhibits an intermittent interseasonal frequency (3–6 months), especially during three periods (1983–84, 1990, and 1994–96). Some energy is also found with a 4-yr period. Further analyses reveal that the pulsation mode can also be observed in physical space. The pulsation mode is found to be related to movements of the SAF constrained by the bathymetry of the Southeast Indian Ridge. The pulsation mode displays many similarities with cold-core eddy events rather than being related to variations of the westerly wind stress, as previously proposed. The impact of those events on SAMW properties remains unclear.

Application of novel trace analysis methods for lignin and levoglucosan in flowstone samples from New Zealand during the Holocene

2020 ◽  
Author(s):  
Anja Beschnitt ◽  
Thorsten Hoffmann
Keyword(s):  
New Zealand ◽  
Trace Analysis ◽  
Negative Temperature ◽  
Graphitized Carbon Black ◽  
Ion Source ◽  
Oxidation Products ◽  
Climate Conditions ◽  
The Holocene ◽  
Analysis Methods ◽  
Stable Conditions

&lt;p&gt;Speleothems are secondary mineral deposits found in caves. They can grow continuously over 1,000-10,000 years and the &lt;sup&gt;230&lt;/sup&gt;Th/U method allows accurate dating back to 500,000 years.[1] Stable conditions in caves preserve organic matter, making speleothems highly valuable climate archives. The high interest in expanding the range of organic proxies in speleothems requires highly sensitive analytical techniques. Novel trace analysis methods for lignin and levoglucosan in speleothems were established according to principles of &quot;Green Chemistry&quot; [2] and applied to flowstone samples from different caves in New Zealand during the Holocene.&lt;/p&gt;&lt;p&gt;Lignin is the second most abundant biopolymer after cellulose. It consists of three monomers, which are included into the polymer in different ratios, depending on the type of vegetation. It is found in speleothems and quantification in timely consecutive layers allows drawing conclusions on changing types and amount of vegetations above the caves, which are influenced by climate conditions like temperature and rainfall.[3] To analyse the monomeric composition, lignin has to be degraded by an alkaline oxidation. Thereby the monomers are oxidized into lignin oxidation products which are then analysed by uHPLC-ESI-HRMS. To date, lignin degradation was conducted using Cu(II)O as a catalyst, which was replaced by CuSO&lt;sub&gt;4&lt;/sub&gt;, eliminating the solid, toxic Cu(II)O waste, and highly reducing the amount of artefacts and used chemicals during sample preparation. The new method was successfully applied to the flowstone samples but posed further questions on the transport of lignin through the soil into the speleothem.[4],[5]&amp;#160; &amp;#160;&lt;/p&gt;&lt;p&gt;The other proxy of interest was levoglucosan, an anhydrosugar formed by cellulose combustion. For temperature studies in speleothems carbon isotopes are used which can be influenced by e.g. fire events. Therefore, it is necessary to introduce a proxy, which prevents falsely positive or negative temperature trends. Extraction of levoglucosan was conducted using graphitized carbon black and chromatographic separation by a hydrophilic interaction liquid chromatography, using a post-column flow to increase the ionization efficiency in the ESI ion source. Levoglucosan analysis was introduced into the existing workflow, without interfering with lignin analysis, and thereby a multi-proxy approach was developed. This work showed that levoglucosan is present in speleothems in quantifiable amounts. It was detected in two of the study sites, showing no correlation to lignin. A plant-based origin of levoglucosan was ruled out, suggesting a fire-related entry into the speleothem.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;[1] Baker, A., et al. (2008). International Journal of Speleology, 37 (3), 193-206; [2] Anastas, P., Eghbali, N. (2010), Chemical Society Reviews, 39, 301-312; [3] Hedges, J., Mann, D. (1979). Geochimica et Cosmochimica Acta, 43 (11), 1803-1807; [4] Heidke, I., Scholz, D., Hoffmann, T. (2018). Biogeosciences, 15 (19), 5831-5845; [5] Yan, G., Kaiser, K. (2018). Analytical Chemistry , 90 (15), 9289-9295&lt;/p&gt;

ON EVALUATION OF THE ROLE OF THERMAL AND WIND FACTORS FOR A PHYSICAL MODEL OF THE WORLD OCEAN GENERAL CIRCULATION SYSTEM

2019 ◽  
Vol 47 (3) ◽  
pp. 80-91
Author(s):  
V. G. Neiman
Keyword(s):  
Physical Model ◽  
Ocean Circulation ◽  
General Circulation ◽  
World Ocean ◽  
Circulation System ◽  
The Public ◽  
The World ◽  
Almost All ◽  
Conceptual Foundations

The main content of the work consists of certain systematization and addition of longexisting, but eventually deformed and partly lost qualitative ideas about the role of thermal and wind factors that determine the physical mechanism of the World Ocean’s General Circulation System (OGCS). It is noted that the conceptual foundations of the theory of the OGCS in one form or another are contained in the works of many well-known hydrophysicists of the last century, but the aggregate, logically coherent description of the key factors determining the physical model of the OGCS in the public literature is not so easy to find. An attempt is made to clarify and concretize some general ideas about the two key blocks that form the basis of an adequate physical model of the system of oceanic water masses motion in a climatic scale. Attention is drawn to the fact that when analyzing the OGCS it is necessary to take into account not only immediate but also indirect effects of thermal and wind factors on the ocean surface. In conclusion, it is noted that, in the end, by the uneven flow of heat to the surface of the ocean can be explained the nature of both external and almost all internal factors, in one way or another contributing to the excitation of the general, or climatic, ocean circulation.

scholarly journals Ashinkailepas kermadecensis, a new species of deep-sea scalpelliform barnacle (Thoracica: Eolepadidae) from the Kermadec Islands, southwest Pacific

Zootaxa ◽  
2009 ◽  
Vol 2021 (1) ◽  
pp. 57-65 ◽  
Author(s):  
JOHN S. BUCKERIDGE
Keyword(s):  
New Species ◽  
New Zealand ◽  
Deep Sea ◽  
Cold Water ◽  
The Other ◽  
Cold Seeps ◽  
Central Japan ◽  
Southwest Pacific ◽  
The North ◽  
A New Species

A new deep-sea stalked barnacle, Ashinkailepas kermadecensis sp. nov. has been recovered from a cold-water seep at depths of 1165 metres in the vicinity of the Kermadec Ridge to the northeast of the North Island, New Zealand. There are now two species of Ashinkailepas—the other, Ashinkailepas seepiophila Yamaguchi, Newman & Hashimoto, 2004, occurs in deep, cold seeps off central Japan. As there are two species within Ashinkailepas, formal diagnoses are provided for both taxa.

scholarly journals Impacts of Modifications to a Local Planetary Boundary Layer Scheme on Forecasts of the Great Plains Low-Level Jet Environment

2018 ◽  
Vol 33 (5) ◽  
pp. 1109-1120 ◽  
Author(s):  
David E. Jahn ◽  
William A. Gallus
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Planetary Boundary Layer ◽  
Great Plains ◽  
Potential Temperature ◽  
Specific Humidity ◽  
Low Level ◽  
Stable Conditions ◽  
Pbl Scheme ◽  
Low Level Jet

Abstract The Great Plains low-level jet (LLJ) is influential in the initiation and evolution of nocturnal convection through the northward advection of heat and moisture, as well as convergence in the region of the LLJ nose. However, accurate numerical model forecasts of LLJs remain a challenge, related to the performance of the planetary boundary layer (PBL) scheme in the stable boundary layer. Evaluated here using a series of LLJ cases from the Plains Elevated Convection at Night (PECAN) program are modifications to a commonly used local PBL scheme, Mellor–Yamada–Nakanishi–Niino (MYNN), available in the Weather Research and Forecasting (WRF) Model. WRF forecast mean absolute error (MAE) and bias are calculated relative to PECAN rawinsonde observations. The first MYNN modification invokes a new set of constants for the scheme closure equations that, in the vicinity of the LLJ, decreases forecast MAEs of wind speed, potential temperature, and specific humidity more than 19%. For comparison, the Yonsei University (YSU) scheme results in wind speed MAEs 22% lower but specific humidity MAEs 17% greater than in the original MYNN scheme. The second MYNN modification, which incorporates the effects of potential kinetic energy and uses a nonzero mixing length in stable conditions as dependent on bulk shear, reduces wind speed MAEs 66% for levels below the LLJ, but increases MAEs at higher levels. Finally, Rapid Refresh analyses, which are often used for forecast verification, are evaluated here and found to exhibit a relatively large average wind speed bias of 3 m s−1 in the region below the LLJ, but with relatively small potential temperature and specific humidity biases.

Sources and transport of glacial meltwater in the Bellingshausen Sea, Antarctica

2021 ◽  
Author(s):  
Peter Sheehan ◽  
Karen Heywood ◽  
Andrew Thompson ◽  
Mar Flexas
Keyword(s):  
Ocean Circulation ◽  
World Ocean ◽  
Cyclonic Circulation ◽  
Shelf Break ◽  
Multiple Sources ◽  
Ice Shelf ◽  
Transport Pathways ◽  
Ice Shelves ◽  
Bellingshausen Sea ◽  
The Impact

&lt;p&gt;Quantifying meltwater content and describing transport pathways is important for understanding the impact of a warming, melting Antarctica on ocean circulation. Meltwater fluxes can affect density-driven, on-shelf flows around the continent, and the formation of the dense water masses that ventilate abyssal regions of the world ocean. We present observations collected from two ocean gliders that were deployed in the Bellingshausen Sea for a period of 10 weeks between January and March of 2020.&lt;span&gt;&amp;#160; &lt;/span&gt;Using multiple high-resolution sections, we quantify both the distribution of meltwater concentrations and lateral meltwater fluxes within the Belgica Trough in the Bellingshausen Sea. We observe a cyclonic circulation in the trough, in agreement with previous studies. A meltwater flux of 0.46 mSv is observed flowing northwards in the&lt;span&gt;&amp;#160; &lt;/span&gt;western limb of the cyclonic circulation. A newly identified meltwater re-circulation (0.88 mSv) is observed flowing back towards the ice front (i.e. southwards) with the eastern limb of the cyclonic circulation. In addition, 1.16 mSv of meltwater is observed flowing northeastward, parallel to the shelf break, with the northern limb of the cyclonic circulation. Peak meltwater is concentrated into two layers associated with different density surfaces: one approximately 150 m deep (27.4 kg m&lt;sup&gt;-3&lt;/sup&gt;) and one approximately 200 m deep (27.6 kg m&lt;sup&gt;-3&lt;/sup&gt;}). The deeper of these layers is characterised by an elevated optical backscatter, which indicates a more turbid water mass. The shallower layer is less turbid, and is more prominent closer to the shelf break and in the eastern part of the Belgica Trough. We hypothesise that the deeper, turbid meltwater layer originates locally from the Venables Ice Shelf, whereas the shallower, less turbid meltwater layer, comprises meltwater from ice shelves in the eastern Bellingshausen Sea. The broad distribution of meltwater from multiple sources suggests the potential for remote interactions and feedbacks between the various ice shelves that abut the Bellingshausen Sea.&lt;/p&gt;

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