scholarly journals Calcification morphotypes of the coccolithophorid Emiliania huxleyi in the Southern Ocean: changes in 2001 to 2006 compared to historical data

2007 ◽  
Vol 348 ◽  
pp. 47-54 ◽  
Author(s):  
JC Cubillos ◽  
SW Wright ◽  
G Nash ◽  
MF de Salas ◽  
B Griffiths ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Historical Data ◽  
Emiliania Huxleyi

scholarly journals Extracting Climatic Information From Observations Of Icebergs In The Southern Ocean

1990 ◽  
Vol 14 ◽  
pp. 352-352 ◽  
Author(s):  
Olav Orheim
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Mass Balance ◽  
Historical Data ◽  
Snow Accumulation ◽  
Selective Reporting ◽  
List Type ◽  
The Past ◽  
Iceberg Calving ◽  
Climatic Information

Antarctic iceberg observations provide two types of climatic information: (1) the rate of iceberg calving gives the main negative term in the mass balance of Antarctica; (2) the distribution of icebergs in the Southern Ocean is related to various factors including sea-ice extent and ocean conditions. This paper discusses climatic information obtained both from modern iceberg observations, and from historical data.The main modern data source is the international iceberg observation programme, initiated in 1981. This has generated a database which now contains observations of size and position of 150 000 icebergs in the Southern Ocean. Other recent data sources include observations from 1974 of icebergs of over 22 km length by the Navy/NOAA Joint Ice Center (which now total nearly 100 bergs). Historical sources include both scientific and commercial (whaling) expeditions.Three conclusions can be drawn from the recent iceberg data. (1)For the past seven years annual calving rates of icebergs less than 22 km in length have been approximately constant both in numbers and total mass, and have exceeded the annual mean mass of bergs over 22 km calved during the same period.(2)The annually-calved mass of gigantic icebergs of length over 22 km, has varied more than two orders of magnitude during the past two decades. The mass of calved gigantic icebergs alone exceeded continental snow accumulation in 1967, 1986 and 1987.(3)Mean iceberg calving rate exceeds continental snow accumulation rate.These results are discussed in relation to Antarctic mass balance and sea level.Historical observations of iceberg distributions in the Southern Ocean differ from recent observations by showing: (i) higher frequencies of bergs at lower latitudes, (ii) a larger proportion of large bergs, and (iii) a more uniform iceberg distribution throughout the region. Comparisons between past and present distribution patterns indicate that there must be errors, including exaggerations and selective reporting, in the historical data. Such observations should therefore not be used uncritically to make climatic conclusions.Bearing in mind the potential flaws in historical data there still appears to be real variations with time in iceberg distribution. These include higher frequencies of bergs at lower latitudes during the past century and the first decades of this century, than at present. Expanded northern range of the bergs would occur if one or more of the following conditions then applied: (1) calved icebergs were larger; (2) sea ice was more extensive in time and space; (3) ocean temperatures were lower; (4) ocean (wind) conditions were such that northward advection rates were higher. The importance of each of these conditions is discussed.

scholarly journals Drift patterns in an Antarctic channel from a quasi-geostrophic model with surface friction

1998 ◽  
Vol 27 ◽  
pp. 501-506 ◽  
Author(s):  
Jörg-Olaf Wolff ◽  
John A.T. Bye
Keyword(s):  
Southern Ocean ◽  
Historical Data ◽  
Wind Waves ◽  
Surface Current ◽  
Surface Friction ◽  
Stokes Drift ◽  
Synoptic Variability ◽  
Waves And Currents ◽  
Fine Resolution ◽  
Fluctuating Wind

The surface layer of the Southern Ocean is subject to the action of wind, waves and currents. We present solutions from a fine-resolution quasi-geostrophic model with surface friction, which is driven by a specified mean and fluctuating wind field, and predicts the surface current, and also the surface Stokes drift due to the wavefield. The resulting flow patterns control the dispersion of particles at the sea surface, and, using a proven Lagrangian algorithm, batches of particles of specified draught can be injected into the flow at various locations and tracked. The simulated patterns are compared with historical data on dispersion and with drift-card and satellite-drogue studies in the Southern Ocean, iceberg tracking and other studies to show the relative importance of dispersion by synoptic variability in the atmosphere and mesoscale eddies in the ocean.

scholarly journals The influence of environmental variability on the biogeography of coccolithophores and diatoms in the Great Calcite Belt

2017 ◽  
Vol 14 (21) ◽  
pp. 4905-4925 ◽  
Author(s):  
Helen E. K. Smith ◽  
Alex J. Poulton ◽  
Rebecca Garley ◽  
Jason Hopkins ◽  
Laura C. Lubelczyk ◽  
...  
Keyword(s):  
Species Composition ◽  
Southern Ocean ◽  
Silicic Acid ◽  
Mixed Layer ◽  
Dissolved Inorganic Carbon ◽  
Emiliania Huxleyi ◽  
The South ◽  
Carbonate Chemistry ◽  
Atlantic Sector ◽  
South Indian

Abstract. The Great Calcite Belt (GCB) of the Southern Ocean is a region of elevated summertime upper ocean calcite concentration derived from coccolithophores, despite the region being known for its diatom predominance. The overlap of two major phytoplankton groups, coccolithophores and diatoms, in the dynamic frontal systems characteristic of this region provides an ideal setting to study environmental influences on the distribution of different species within these taxonomic groups. Samples for phytoplankton enumeration were collected from the upper mixed layer (30 m) during two cruises, the first to the South Atlantic sector (January–February 2011; 60° W–15° E and 36–60° S) and the second in the South Indian sector (February–March 2012; 40–120° E and 36–60° S). The species composition of coccolithophores and diatoms was examined using scanning electron microscopy at 27 stations across the Subtropical, Polar, and Subantarctic fronts. The influence of environmental parameters, such as sea surface temperature (SST), salinity, carbonate chemistry (pH, partial pressure of CO2 (pCO2), alkalinity, dissolved inorganic carbon), macronutrients (nitrate + nitrite, phosphate, silicic acid, ammonia), and mixed layer average irradiance, on species composition across the GCB was assessed statistically. Nanophytoplankton (cells 2–20 µm) were the numerically abundant size group of biomineralizing phytoplankton across the GCB, with the coccolithophore Emiliania huxleyi and diatoms Fragilariopsis nana, F. pseudonana, and Pseudo-nitzschia spp. as the most numerically dominant and widely distributed. A combination of SST, macronutrient concentrations, and pCO2 provided the best statistical descriptors of the biogeographic variability in biomineralizing species composition between stations. Emiliania huxleyi occurred in silicic acid-depleted waters between the Subantarctic Front and the Polar Front, a favorable environment for this species after spring diatom blooms remove silicic acid. Multivariate statistics identified a combination of carbonate chemistry and macronutrients, covarying with temperature, as the dominant drivers of biomineralizing nanoplankton in the GCB sector of the Southern Ocean.

scholarly journals Limited variability in the phytoplankton Emiliania huxleyi since the pre-industrial era in the Subantarctic Southern Ocean

Anthropocene ◽  
2020 ◽  
Vol 31 ◽  
pp. 100254
Author(s):  
A.S. Rigual-Hernández ◽  
J.M. Sánchez-Santos ◽  
R. Eriksen ◽  
A.D. Moy ◽  
F.J. Sierro ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Emiliania Huxleyi

PHOTOSYNTHETIC PIGMENT AND GENETIC DIFFERENCES BETWEEN TWO SOUTHERN OCEAN MORPHOTYPES OF EMILIANIA HUXLEYI (HAPTOPHYTA)1

2011 ◽  
Vol 47 (3) ◽  
pp. 615-626 ◽  
Author(s):  
Suellen S. Cook ◽  
Lucy Whittock ◽  
Simon W. Wright ◽  
Gustaaf M. Hallegraeff
Keyword(s):  
Southern Ocean ◽  
Photosynthetic Pigment ◽  
Emiliania Huxleyi ◽  
Genetic Differences

scholarly journals Extracting Climatic Information From Observations Of Icebergs In The Southern Ocean

1990 ◽  
Vol 14 ◽  
pp. 352 ◽  
Author(s):  
Olav Orheim
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Mass Balance ◽  
Historical Data ◽  
Snow Accumulation ◽  
Selective Reporting ◽  
List Type ◽  
The Past ◽  
Iceberg Calving ◽  
Climatic Information

Antarctic iceberg observations provide two types of climatic information: (1) the rate of iceberg calving gives the main negative term in the mass balance of Antarctica; (2) the distribution of icebergs in the Southern Ocean is related to various factors including sea-ice extent and ocean conditions. This paper discusses climatic information obtained both from modern iceberg observations, and from historical data. The main modern data source is the international iceberg observation programme, initiated in 1981. This has generated a database which now contains observations of size and position of 150 000 icebergs in the Southern Ocean. Other recent data sources include observations from 1974 of icebergs of over 22 km length by the Navy/NOAA Joint Ice Center (which now total nearly 100 bergs). Historical sources include both scientific and commercial (whaling) expeditions. Three conclusions can be drawn from the recent iceberg data. (1) For the past seven years annual calving rates of icebergs less than 22 km in length have been approximately constant both in numbers and total mass, and have exceeded the annual mean mass of bergs over 22 km calved during the same period. (2) The annually-calved mass of gigantic icebergs of length over 22 km, has varied more than two orders of magnitude during the past two decades. The mass of calved gigantic icebergs alone exceeded continental snow accumulation in 1967, 1986 and 1987. (3) Mean iceberg calving rate exceeds continental snow accumulation rate. These results are discussed in relation to Antarctic mass balance and sea level. Historical observations of iceberg distributions in the Southern Ocean differ from recent observations by showing: (i) higher frequencies of bergs at lower latitudes, (ii) a larger proportion of large bergs, and (iii) a more uniform iceberg distribution throughout the region. Comparisons between past and present distribution patterns indicate that there must be errors, including exaggerations and selective reporting, in the historical data. Such observations should therefore not be used uncritically to make climatic conclusions. Bearing in mind the potential flaws in historical data there still appears to be real variations with time in iceberg distribution. These include higher frequencies of bergs at lower latitudes during the past century and the first decades of this century, than at present. Expanded northern range of the bergs would occur if one or more of the following conditions then applied: (1) calved icebergs were larger; (2) sea ice was more extensive in time and space; (3) ocean temperatures were lower; (4) ocean (wind) conditions were such that northward advection rates were higher. The importance of each of these conditions is discussed.

Has (anthropogenic) climate change driven subantarctic Emiliania huxleyi populations beyond their natural state?

2021 ◽  
Author(s):  
Andres S. Rigual-Hernandez ◽  
Francisco J. Sierro ◽  
José A. Flores ◽  
José M. Sánchez-Santos ◽  
Ruth S. Eriksen ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Environmental Change ◽  
Ocean Acidification ◽  
Emiliania Huxleyi ◽  
Global Ocean ◽  
Natural State ◽  
Sedimentary Record ◽  
Subtle Change ◽  
Assemblage Composition ◽  
Biogeographical Distribution

<p>The global ocean acts as a climate regulator through the uptake of Earth’s excess heat and the absorption of about 30% of anthropogenic CO<sub>2</sub> emissions since 1750.  Southern Ocean waters are warming faster than the global ocean average and their low temperatures and moderate alkalinity make this region especially vulnerable to ocean acidification. Coccolithophores are a major group of calcifying phytoplankton and an important component of the Southern Ocean carbon cycle. Controlled laboratory experiments on <em>Emiliania huxleyi </em>(the most abundant coccolithophore) over a broad range of carbonate chemistry scenarios suggest that this taxon may be susceptible to ongoing environmental change. However, it remains uncertain whether Southern Ocean coccolithophore populations have been modified by environmental change during the industrial era. The main reason for this knowledge gap is the lack of observational data since the onset of the Industrial Revolution. In particular, continuous monitoring of key Southern Ocean ecosystems only started a few decades ago, a period insufficiently long to permit assessments of whether anthropogenic impacts on the environment have affected coccolithophore populations beyond their natural state. In order to overcome this limitation, here we take advantage of the preservation capacity of coccolithophores in the sedimentary record to provide a benchmark of their pre-industrial state. We compare the morphotype assemblage composition and morphometric parameters in coccoliths of <em>E. huxleyi </em>from a suite of Holocene-aged sediments south of Tasmania with annual sediment trap records retrieved at the Southern Ocean Time Series observatory in the Australian sector of the Subantarctic Zone. Our results suggest that carbonate dissolution in the sediments reduced the coccolith mass and length of the coccoliths but, coccolith thickness appeared to be decoupled from dissolution. The biogeographical distribution of coccolith thickness in subtropical and subantarctic sediments mirrored the distribution of E. huxleyi morphotypes, highlighting the important role of <em>E. huxleyi </em>assemblage composition on the control of coccolith morphometrics. Moreover, comparison of coccolith assemblages from the sedimentary record with those collected from subantarctic sediment traps indicates that modern E. huxleyi coccoliths are about 2% thinner than those from the pre-industrial Holocene. The subtle change in coccolith thickness is in stark contrast with previous work that documented a dramatic reduction in shell calcification in the planktonic foraminifera <em>Globigerina bulloides </em>that resulted in a shell-weight decrease of 30-35%, most likely induced by ocean acidification. Overall, our results underscore the variable sensitivity of different marine calcifying plankton groups to ongoing environmental change in the Southern Ocean.</p>

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