scholarly journals Highly branched isoprenoids for Southern Ocean sea ice reconstructions: a pilot study from the Western Antarctic Peninsula

2019 ◽  
Vol 16 (15) ◽  
pp. 2961-2981 ◽  
Author(s):  
Maria-Elena Vorrath ◽  
Juliane Müller ◽  
Oliver Esper ◽  
Gesine Mollenhauer ◽  
Christian Haas ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Antarctic Peninsula ◽  
Environmental Changes ◽  
Transfer Functions ◽  
Drake Passage ◽  
Ice Cover ◽  
The Arctic ◽  
Western Antarctic Peninsula ◽  
Instrumental Records

Abstract. Organic geochemical and micropaleontological analyses of surface sediments collected in the southern Drake Passage and the Bransfield Strait, Western Antarctic Peninsula, enable a proxy-based reconstruction of recent sea ice conditions in this climate-sensitive area. We study the distribution of the sea ice biomarker IPSO25, and biomarkers of open marine environments such as more unsaturated highly branched isoprenoid alkenes and phytosterols. Comparison of the sedimentary distribution of these biomarker lipids with sea ice data obtained from satellite observations and diatom-based sea ice estimates provide for an evaluation of the suitability of these biomarkers to reflect recent sea surface conditions. The distribution of IPSO25 supports earlier suggestions that the source diatom seems to be common in near-coastal environments characterized by annually recurring sea ice cover, while the distribution of the other biomarkers is highly variable. Offsets between sea ice estimates deduced from the abundance of biomarkers and satellite-based sea ice data are attributed to the different time intervals recorded within the sediments and the instrumental records from the study area, which experienced rapid environmental changes during the past 100 years. To distinguish areas characterized by permanently ice-free conditions, seasonal sea ice cover and extended sea ice cover, we apply the concept of the PIP25 index from the Arctic Ocean to our data and introduce the term PIPSO25 as a potential sea ice proxy. While the trends in PIPSO25 are generally consistent with satellite sea ice data and winter sea ice concentrations in the study area estimated by diatom transfer functions, more studies on the environmental significance of IPSO25 as a Southern Ocean sea ice proxy are needed before this biomarker can be applied for semi-quantitative sea ice reconstructions.

scholarly journals Highly branched isoprenoids for Southern Ocean semi-quantitative sea ice reconstructions: a pilot study from the Western Antarctic Peninsula

2019 ◽  
Author(s):  
Maria-Elena Vorrath ◽  
Juliane Müller ◽  
Oliver Esper ◽  
Gesine Mollenhauer ◽  
Christian Haas ◽  
...  
Keyword(s):  
Sea Ice ◽  
Antarctic Peninsula ◽  
Environmental Changes ◽  
Transfer Functions ◽  
Drake Passage ◽  
Ice Cover ◽  
Time Intervals ◽  
Ice Conditions ◽  
Instrumental Records ◽  
Diatom Transfer Functions

Abstract. Organic geochemical and micropaleontological analyses of surface sediments collected in the southern Drake Passage and the Bransfield Strait, Antarctic Peninsula, enable a proxy-based reconstruction of recent sea ice conditions in this climate sensitive area. The distribution of the sea ice biomarker IPSO25 supports earlier suggestions that the source diatoms seem to be common in near-coastal environments characterized by an annually recurring sea ice cover. We here propose and evaluate the combination of IPSO25 with a more unsaturated highly branched isoprenoid alkene and phytosterols and introduce the PIPSO25 index as a potentially semi-quantitative sea ice proxy. This organic geochemical approach is complemented with diatom data. PIPSO25 sea ice estimates are used to discriminate between areas characterized by permanently ice-free conditions, seasonal sea ice cover and extended sea ice cover. These trends are consistent with satellite sea ice data and winter sea ice concentrations estimated by diatom transfer functions. Minor offsets between proxy-based and satellite-based sea ice data are attributed to the different time intervals recorded within the sediments and the instrumental records from the study area, which experienced rapid environmental changes during the past 100 years.

scholarly journals Sea ice drift in the Southern Ocean: Regional patterns, variability, and trends

Elem Sci Anth ◽  
2017 ◽  
Vol 5 ◽  
Author(s):  
Ron Kwok ◽  
Shirley S. Pang ◽  
Sahra Kacimi
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Sea Level ◽  
Ice Cover ◽  
The Arctic ◽  
Positive Trend ◽  
Amundsen Sea ◽  
Regional Patterns ◽  
Ice Drift ◽  
Sea Ice Drift

Understanding long-term changes in large-scale sea ice drift in the Southern Ocean is of considerable interest given its contribution to ice extent, to ice production in open waters, with associated dense water formation and heat flux to the atmosphere, and thus to the climate system. In this paper, we examine the trends and variability of this ice drift in a 34-year record (1982–2015) derived from satellite observations. Uncertainties in drift (~3 to 4 km day–1) were assessed with higher resolution observations. In a linear model, drift speeds were ~1.4% of the geostrophic wind from reanalyzed sea-level pressure, nearly 50% higher than that of the Arctic. This result suggests an ice cover in the Southern Ocean that is thinner, weaker, and less compact. Geostrophic winds explained all but ~40% of the variance in ice drift. Three spatially distinct drift patterns were shown to be controlled by the location and depth of atmospheric lows centered over the Amundsen, Riiser-Larsen, and Davis seas. Positively correlated changes in sea-level pressures at the three centers (up to 0.64) suggest correlated changes in the wind-driven drift patterns. Seasonal trends in ice edge are linked to trends in meridional winds and also to on-ice/off-ice trends in zonal winds, due to zonal asymmetry of the Antarctic ice cover. Sea ice area export at flux gates that parallel the 1000-m isobath were extended to cover the 34-year record. Interannual variability in ice export in the Ross and Weddell seas linked to the depth and location of the Amundsen Sea and Riiser-Larsen Sea lows to their east. Compared to shorter records, where there was a significant positive trend in Ross Sea ice area flux, the longer 34-year trends of outflow from both seas are now statistically insignificant.

scholarly journals Impact of sea ice on the marine iron cycle and phytoplankton productivity

2014 ◽  
Vol 11 (17) ◽  
pp. 4713-4731 ◽  
Author(s):  
S. Wang ◽  
D. Bailey ◽  
K. Lindsay ◽  
J. K. Moore ◽  
M. Holland
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Ice Cover ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Phytoplankton Production ◽  
Iron Cycle ◽  
Surface Ocean ◽  
Antarctic Sea Ice ◽  
Iron Concentrations

Abstract. Iron is a key nutrient for phytoplankton growth in the surface ocean. At high latitudes, the iron cycle is closely related to the dynamics of sea ice. In recent decades, Arctic sea ice cover has been declining rapidly and Antarctic sea ice has exhibited large regional trends. A significant reduction of sea ice in both hemispheres is projected in future climate scenarios. In order to adequately study the effect of sea ice on the polar iron cycle, sea ice bearing iron was incorporated in the Community Earth System Model (CESM). Sea ice acts as a reservoir for iron during winter and releases the trace metal to the surface ocean in spring and summer. Simulated iron concentrations in sea ice generally agree with observations in regions where iron concentrations are relatively low. The maximum iron concentrations simulated in Arctic and Antarctic sea ice are much lower than observed, which is likely due to underestimation of iron inputs to sea ice or missing mechanisms. The largest iron source to sea ice is suspended sediments, contributing fluxes of iron of 2.2 × 108 mol Fe month−1 in the Arctic and 4.1 × 106 mol Fe month−1 in the Southern Ocean during summer. As a result of the iron flux from ice, iron concentrations increase significantly in the Arctic. Iron released from melting ice increases phytoplankton production in spring and summer and shifts phytoplankton community composition in the Southern Ocean. Results for the period of 1998 to 2007 indicate that a reduction of sea ice in the Southern Ocean will have a negative influence on phytoplankton production. Iron transport by sea ice appears to be an important process bringing iron to the central Arctic. The impact of ice to ocean iron fluxes on marine ecosystems is negligible in the current Arctic Ocean, as iron is not typically the growth-limiting nutrient. However, it may become a more important factor in the future, particularly in the central Arctic, as iron concentrations will decrease with declining sea ice cover and transport.

Multiproxy climate and sea ice reconstruction of the industrial era at the Western Antarctic Peninsula

2020 ◽  
Author(s):  
Maria-Elena Vorrath ◽  
Paola Cárdenas ◽  
Lorena Rebolledo ◽  
Xiaoxu Shi ◽  
Juliane Müller ◽  
...  
Keyword(s):  
Sea Ice ◽  
Antarctic Peninsula ◽  
System Analysis ◽  
Ice Cover ◽  
Weddell Sea ◽  
Water Masses ◽  
Western Antarctic Peninsula ◽  
Climate Conditions ◽  
Ice Conditions ◽  
Bransfield Basin

<p>Recent changes and variability in climate conditions leave a significant footprint on the distribution and properties of sea ice, as it is sensitive to environmental variations. We investigate the rapidly transforming region of the Western Antarctic Peninsula (WAP) focusing on the conditions and development of sea ice in the pre-satellite era. For this study on past sea ice cover we apply the novel proxy IPSO<sub>25</sub> (Ice Proxy for the Southern Ocean with 25 carbon atoms; Belt et al., 2016). Three sampling sites were selected to cover areas near the Antarctic mainland, in the Bransfield Basin (2000 m depth) and the deeper shelf under an oceanographic frontal system. Analysis of short cores (multicores) resolving the last 200 years (based on <sup>210</sup>Pb<sub>ex</sub> dating) focused on geochemical bulk parameters, biomarkers (highly branched isoprenoids, GDGTs, sterols) and diatoms. These results are compared to multiple climate archives and modelled data. This multiproxy based approach provides insights on changes in spring sea ice cover, primary production regimes, subsurface ocean temperature (SOT based on TEX<sup>L</sup><sub>86</sub>) and oceanographic as well as atmospheric circulation patterns. While environmental proxies preserved in two cores near the coast and in the Bransfield Basin reflect the properties of water masses from the Bellingshausen Sea and Weddell Sea, respectively, data from the third core at the deeper shelf depict mixed signals of both water masses. Our study reveals clear evidence for warm and cold periods matching with ice core records and other marine sediment data at the WAP. We observe a general decrease in SOT and an increase in sea ice cover overprinted by high decadal fluctuations. Trends in SOT seem to be decoupled from atmospheric temperatures in the 20<sup>th</sup> century, and this is supported by previous studies (e.g. Barbara et al., 2013), and may be related to the Southern Annual Mode. We consider numerical modelling of sea ice conditions, sea surface temperature and SOT for further support of our findings.</p><p> </p><p>References:</p><p>Barbara, L., Crosta, X., Schmidt, S. and Massé, G.: Diatoms and biomarkers evidence for major changes in sea ice conditions prior the instrumental period in Antarctic Peninsula, Quat. Sci. Rev., 79, 99–110, doi:10.1016/j.quascirev.2013.07.021, 2013.</p><p>Belt, S. T., Smik, L., Brown, T. A., Kim, J. H., Rowland, S. J., Allen, C. S., Gal, J. K., Shin, K. H., Lee, J. I. and Taylor, K. W. R.: Source identification and distribution reveals the potential of the geochemical Antarctic sea ice proxy IPSO25, Nat. Commun., 7, 1–10, doi:10.1038/ncomms12655, 2016.</p>

scholarly journals Inter-annual variations observed in spring and summer Antarctic sea ice extent in recent decade

MAUSAM ◽  
2021 ◽  
Vol 62 (4) ◽  
pp. 633-640
Author(s):  
SANDIP R.OZA ◽  
R.K.K. SINGH ◽  
ABHINAV SRIVASTAVA ◽  
MIHIR K.DASH ◽  
I.M.L. DAS ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Large Scale ◽  
Ross Sea ◽  
Ice Cover ◽  
Weddell Sea ◽  
The Arctic ◽  
Sea Ice Extent ◽  
Antarctic Sea Ice ◽  
The Antarctic

The growth and decay of sea ice are complex processes and have important feedback onto the oceanic and atmospheric circulation. In the Antarctic, sea ice variability significantly affects the primary productivity in the Southern Ocean and thereby negatively influences the performance and survival of species in polar ecosystem. In present days, the awareness on the sea ice variability in the Antarctic is not as matured as it is for the Arctic region. The present paper focuses on the inter-annual trends (1999-2009) observed in the monthly fractional sea ice cover in the Antarctic at 1 × 1 degree level, for the November and February months, derived from QuikSCAT scatterometer data. OSCAT scatterometer data from India’s Oceansat-2 satellite were used to asses the sea ice extent (SIE) observed in the month of November 2009 and February 2010 and its deviation from climatic maximum (1979-2002) sea ice extent (CMSIE). Large differences were observed between SIE and CMSIE, however, trend results show that it is due to the high inter-annual variability in sea ice cover. Spatial distribution of trends show the existence of positive and negative trends in the parts of Western Pacific Ocean, Ross Sea, Amundsen and Bellingshausen Seas (ABS), Weddell Sea and Indian ocean sector of southern ocean. Sea ice trends are compared with long-term SST trends (1982-2009) observed in the austral summer month of February. Large-scale cooling trend observed around Ross Sea and warming trend in ABS sector are the distinct outcome of the study.

scholarly journals Sea Ice dynamics at the Western Antarctic Peninsula during the industrial era: a multi-proxy intercomparison study

2020 ◽  
Author(s):  
Maria-Elena Vorrath ◽  
Juliane Müller ◽  
Lorena Rebolledo ◽  
Paola Cárdenas ◽  
Xiaoxu Shi ◽  
...  
Keyword(s):  
Sea Ice ◽  
Antarctic Peninsula ◽  
Environmental Conditions ◽  
Ice Core ◽  
Ice Cover ◽  
Western Antarctic Peninsula ◽  
Atmospheric Circulation Patterns ◽  
The Past ◽  
Circulation Patterns ◽  
Spring Sea Ice

Abstract. In the last decades, changing climate conditions have had a severe impact on sea ice at the Western Antarctic Peninsula (WAP), an area rapidly transforming under global warming. To study the development of spring sea ice and environmental conditions in the pre-satellite era we investigated three short marine sediment cores for their biomarker inventory with particular focus on the sea ice proxy IPSO25 and micropaleontological proxies. The core sites in the Bransfield Strait are located in shelf to deep basin areas characterized by a complex oceanographic frontal system, coastal influence and sensitivity to large-scale atmospheric circulation patterns. We analyzed geochemical bulk parameters, biomarkers (highly branched isoprenoids, glycerol dialkyl glycerol tetraethers, sterols), and diatom abundances and diversity over the past 200 years (210Pb dating), and compared them to observational data, sedimentary and ice core climate archives as well as results from numerical models. Based on biomarkers we could identify four different stratigraphic units with (1) stable conditions and moderate sea ice cover before 1860, (2) low to moderate sea ice cover between 1860 and 1930, (3) high seasonal variability and changes in sea ice regimes from 1930 to 1990 and (4) a shift to increasing sea ice cover despite anthropogenic warming since 1990. Although IPSO25 concentrations correspond quite well with satellite sea ice observations for the past 40 years, we note discrepancies between the biomarker-based sea ice estimates and the long-term model output for the past 200 years, ice core records and reconstructed atmospheric circulation patterns such as El Niño Southern Oscillation (ENSO) and Southern Annular Mode (SAM). We propose that the sea ice biomarker proxies IPSO25 and PIPSO25 are not linearly related to sea ice cover and, additionally, each core site reflects specific, local environmental conditions. High IPSO25 and PIPSO25 values may not be directly interpreted as referring to high spring sea ice cover because variable sea ice conditions and enhanced nutrient supply may affect the production of both the sea-ice associated and phytoplankton-derived (open marine, pelagic) biomarker lipids. For a more meaningful interpretation we recommend to carefully consider individually biomarker records to distinguish between cold, sea ice favoring and warm, sea ice diminishing environmental conditions.

scholarly journals Radical past climatic changes in the Arctic Ocean and a geophysical signature of the Lomonosov Ridge north of Greenland

2006 ◽  
Vol 10 ◽  
pp. 61-64
Author(s):  
Naja Mikkelsen ◽  
Niels Nørgaard-Pedersen ◽  
Yngve Kristoffersen ◽  
Susanne Juul Lassen ◽  
Emma Sheldon
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Environmental Changes ◽  
Sediment Cores ◽  
Environmental Parameters ◽  
Ice Cover ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Lomonosov Ridge ◽  
The Arctic Ocean

The Arctic Ocean is a landlocked basin, at present covered by perennial sea ice. During the past few decades a significant thinning and shrinking of the sea ice has been observed, and modelling studies indicate that the Arctic Ocean ice cover could, by the end of this century, almost disappear from most parts of the Arctic Ocean during peak summer seasons. It remains uncertain, however, whether the environmental changes are an enhanced greenhouse-warming signal or a result of natural (long-term) variability, but palaeoceanographic studies can contribute to our understanding of the natural variability of environmental parameters, e.g. sea-ice cover and oceanographic changes on time-scales of centuries to millennia. As part of the multidisciplinary EU project Greenland Arctic Shelf Ice and Climate Experiment (GreenICE), sediment coring and seismic reflection measurements have been undertaken in a hitherto unexplored part of the Arctic Ocean, the margin of the Lomonosov Ridge in the Lincoln Sea (Fig. 1). The aim of the project was to study the structure and dynamics of the sea-ice cover and attempt to relate these to longer-term records of climate variability retrieved from sediment cores. The main field work was carried out in May 2004 from an ice camp established by a Twin Otter aircraft on drifting sea ice at 85°N, 65°W, c. 170 km north of Alert, Arctic Canada. The camp was deployed over the shallowest part of the Lomonosov Ridge off the northern Greenland/Canada continental margin (Fig. 1). The sea-ice drift would normally be between east and south, but persistent easterly winds resulted in a fast drift trajectory towards the WSW, such that the camp drifted a distance of approximately 62 km during the two weeks camp period. At present the study area is heavily ice covered, and forecast models of future shrinking Arctic sea-ice cover suggest that this area is one of the least sensitive to warming in the Arctic. The results obtained from the GreenICE project challenge this view.

Antarctic Peninsula sea levels: a real-time system for monitoring Drake Passage transport

2006 ◽  
Vol 18 (3) ◽  
pp. 429-436 ◽  
Author(s):  
P.L. Woodworth ◽  
C.W. Hughes ◽  
D.L. Blackman ◽  
V.N. Stepanov ◽  
S.J. Holgate ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Real Time ◽  
Antarctic Peninsula ◽  
Tide Gauge ◽  
Drake Passage ◽  
Southern Annular Mode ◽  
Time System ◽  
International Polar Year ◽  
Real Time System ◽  
Sea Levels

Sub-surface pressure (SSP) data from tide gauges at three bases on the Pacific coast of the Antarctic Peninsula, together with SSP information from a bottom pressure recorder deployed on the south side of the Drake Passage, have been used to study the relationships between SSP, Drake Passage transport, and the strength of Southern Ocean zonal winds as represented by the Southern Annular Mode. High correlations were obtained between all parameters, confirming results obtained previously with independent data sets, and demonstrating the value of information from the permanent Rothera base, the southern-most site considered. These are important findings with regard to the design, installation and maintenance of observation networks in Antarctica. In particular, they provide the necessary justification for Antarctic Peninsula tide gauge infrastructure investment in the lead up to International Polar Year. Data delivery from Rothera and Vernadsky is currently being improved and should soon enable the first near real-time system for monitoring Drake Passage transport variability on intraseasonal timescales, an essential component of a Southern Ocean Observing System.

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