Tas D van Ommen

Tas D van Ommen
Australian Antarctic Division · Science Branch

Ph.D. (Physics), University of Tasmania

About

338
Publications
51,299
Reads
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10,786
Citations
Citations since 2017
30 Research Items
4983 Citations
20172018201920202021202220230200400600800
20172018201920202021202220230200400600800
20172018201920202021202220230200400600800
20172018201920202021202220230200400600800
Additional affiliations
May 1994 - present
Australian Antarctic Division
Position
  • Antarctic Climate Program Leader
May 1994 - June 2019
Antarctic Climate and Ecosystems Cooperative Research Centre
Position
  • Co-Leader, Oceans and Cryosphere Program
August 1992 - January 1994
California Institute of Technology
Position
  • PostDoc Position

Publications

Publications (338)
Article
Full-text available
Climate variations cause ice sheets to retreat and advance, raising or lowering sea level by metres to decametres. The basic relationship is unambiguous, but the timing, magnitude and sources of sea-level change remain unclear; in particular, the contribution of the East Antarctic Ice Sheet (EAIS) is ill defined, restricting our appreciation of pot...
Article
Full-text available
Future changes in atmospheric circulation and associated modes of variability are a major source of uncertainty in climate projections. Nowhere is this issue more acute than across the mid-latitudes to high latitudes of the Southern Hemisphere (SH), which over the last few decades have experienced extreme and regionally variable trends in precipita...
Article
Full-text available
Accurate high-resolution records of snow accu-mulation rates in Antarctica are crucial for estimating ice sheet mass balance and subsequent sea level change. Snow-fall rates at Law Dome, East Antarctica, have been linked with regional atmospheric circulation to the mid-latitudes as well as regional Antarctic snowfall. Here, we extend the length of...
Article
Full-text available
Over the past 30 years, ice cores from Greenland, and subsequently from Antarctica, have progressively revealed a fascinating and unexpected picture of inter-hemispheric climate behaviour during the last glacial period, approximately 110,000 to 12,000 years ago. In the north, the glacial cold was punctuated by a series of abrupt warming events, eac...
Article
The Interdecadal Pacific Oscillation (IPO) influences multidecadal drought risk across the Pacific, but there are no millennial-length, high resolution IPO reconstructions for quantifying long-term drought risk. In Australia, drought risk increases in positive phases of the IPO, yet few suitable rainfall proxies and short (~100 y) instrumental reco...
Article
Full-text available
Standard proxies for reconstructing surface mass balance (SMB) in Antarctic ice cores are often inaccurate or coarsely resolved when applied to more complicated environments away from dome summits. Here, we propose an alternative SMB proxy based on photolytic fractionation of nitrogen isotopes in nitrate observed at 114 sites throughout East Antarc...
Article
Full-text available
The Princess Elizabeth Land sector of the East Antarctic Ice Sheet is a significant reservoir of grounded ice and is adjacent to regions that experienced great change during Quaternary glacial cycles and Pliocene warm episodes. The existence of an extensive subglacial water system in Princess Elizabeth Land (to date only inferred from satellite ima...
Preprint
Full-text available
Standard proxies for reconstructing surface mass balance (SMB) in Antarctic ice cores are often inaccurate or coarsely resolved when applied to more complicated environments away from dome summits. Here, we propose an alternative SMB proxy based on photolytic fractionation of nitrogen isotopes in nitrate observed at 114 sites throughout East Antarc...
Article
Full-text available
Abstract We present a new simple and efficient method for correlation of unevenly and differently sampled data. This new method overcomes problems with other methods for correlation with non-uniform sampling and is an easy modification to existing correlation based codes. To demonstrate the usefulness of this new method to real-world examples, we a...
Article
Full-text available
The Southern Ocean occupies 14% of the Earth’s surface and plays a fundamental role in the global carbon cycle and climate. It provides a direct connection to the deep ocean carbon reservoir through biogeochemical processes that include surface primary productivity, remineralization at depth and the upwelling of carbon-rich water masses. However, t...
Article
Full-text available
The future response of the Antarctic ice sheet to rising temperatures remains highly uncertain. A useful period for assessing the sensitivity of Antarctica to warming is the Last Interglacial (LIG) (129 to 116 ky), which experienced warmer polar temperatures and higher global mean sea level (GMSL) (+6 to 9 m) relative to present day. LIG sea level...
Article
Full-text available
The Antarctic ice sheet has been losing mass over past decades through the accelerated flow of its glaciers, conditioned by ocean temperature and bed topography. Glaciers retreating along retrograde slopes (that is, the bed elevation drops in the inland direction) are potentially unstable, while subglacial ridges slow down the glacial retreat. Desp...
Article
Full-text available
Glacier-mass changes are a reliable indicator of climate change. On behalf of the worldwide network of glacier observers, we urge parties to the United Nations Framework Convention on Climate Change to boost international cooperation in monitoring these changes, and to include the results in the Paris agreement’s global stocktake.
Article
Full-text available
Determining the feedbacks that modulate Southern Ocean carbon dynamics is key to understanding past and future climate. The global pause in rising atmospheric CO2 during the period of mid- to high-latitude southern surface cooling known as the Antarctic Cold Reversal (ACR, 14,700-12,700 years ago) provides an opportunity to disentangle competing in...
Article
Full-text available
Ice core records of the major atmospheric greenhouse gases (CO2, CH4, N2O) and their isotopologues covering recent centuries provide evidence of biogeochemical variations during the Late Holocene and pre-industrial periods and over the transition to the industrial period. These records come from a number of ice core and firn air sites and have been...
Conference Paper
Full-text available
The Southern Ocean plays a fundamental role in regulating global atmospheric CO2 levels, yet the underlying processes and feedbacks that control the carbon cycle during climate transitions remain unclear. Following the Last Glacial Termination (LGT), the rapid rise in atmospheric CO2 was interrupted by an enigmatic 1,900-year plateau during a perio...
Article
Full-text available
Ice core records of the major atmospheric greenhouse gases (CO2, CH4, N2O) and their isotopologues covering recent centuries provide evidence of biogeochemical variations during the Late-Holocene and Pre-Industrial Periods and over the transition to the Industrial Period. These records come from a number of ice core and firn air sites, and have bee...
Preprint
The future response of the Antarctic ice sheets to rising temperatures remains highly uncertain. A valuable analogue for assessing the sensitivity of Antarctica to warming is the Last Interglacial (129-116 kyr), when global sea level peaked 6 to 9 meters above present. Here we report a blue-ice record of ice-sheet and environmental change from the...
Poster
The Southern Ocean plays a fundamental role in regulating global atmospheric CO2 levels, yet the underlying processes and feedbacks that control carbon cycle during climate transitions remain unclear. Following the last glacial, the rapid and punctuated rise in atmospheric CO2 was interrupted by an enigmatic 1,900-year plateau during a period of pr...
Presentation
Reconstructing the dynamic response of the Antarctic ice sheets to warming during the Last Glacial Termination (LGT; 18,000–11,650 yrs ago) allows us to disentangle ice-climate feedbacks that are key to improving future projections. Whilst the sequence of events during this period is reasonably well known, relatively poor chronological control has...
Article
Full-text available
Climate trends in the Antarctic region remain poorly characterized, owing to the brevity and scarcity of direct climate observations and the large magnitude of interannual to decadal-scale climate variability. Here, within the framework of the PAGES Antarctica2k working group, we build an enlarged database of ice core water stable isotope records f...
Article
Full-text available
Here we present a revised Law Dome, Dome Summit South (DSS) ice core age model (denoted LD2017) that significantly improves the chronology over the last 88 ka. An ensemble approach was used, allowing for the computation of both a median age and associated uncertainty as a function of depth. The revised chronology incorporates extended continuous an...
Article
Full-text available
A large volume of the East Antarctic Ice Sheet drains through the Totten Glacier (TG) and is thought to be a potential source of substantial global sea-level rise over the coming centuries. We show that the surface velocity and height of the floating part of the TG, which buttresses the grounded component, have varied substantially over two decades...
Article
Full-text available
A high-resolution (1 km line spacing) aerogeophysical survey was conducted over a region near the East Antarctic Ice Sheet's Dome C that may hold a 1.5 Myr climate record. We combined new ice thickness data derived from an airborne coherent radar sounder with unpublished data that was in part unavailable for earlier compilations, and we were able t...
Article
Full-text available
The study of (Palmer et al 2015 Environ. Res. Lett. 10 124002) details a spatial reconstruction of drought across eastern Australia and New Zealand over the last 500 years. The authors used a global 0.5° by 0.5° gridded network of the self-calibrating Palmer drought severity index (scPDSI) spanning 1901-2012 as the basis for a nested point-by-point...
Article
Full-text available
A 120 m ice core was drilled on Mill Island, East Antarctica (65°30′ S, 100°40′E) during the 2009/2010 Australian Antarctic field season. Contiguous discrete 5cm samples were measured for hydrogen peroxide, water stable isotopes, and trace ion chemistry. The ice core was annually dated using a combination of chemical species and water stable isotop...
Article
Full-text available
Climate trends in the Antarctic region remain poorly characterised, owing to the brevity and scarcity of direct climate observations and the large magnitude of interannual to decadal-scale climate variability. Here, within the framework of the PAGES Antarctica 2k working group, we build an enlarged database of ice core water stable isotope records...
Article
Full-text available
Reconstructing the dynamic response of the Antarctic ice sheets to warming during the Last Glacial Termination (LGT; 18,000–11,650 yrs ago) allows us to disentangle ice-climate feedbacks that are key to improving future projections. Whilst the sequence of events during this period is reasonably well-known, relatively poor chronological control has...
Article
Black carbon aerosols (BC) are a large source of climate warming, impact atmospheric chemistry, and are implicated in large-scale changes in atmospheric circulation. Inventories of BC emissions suggest significant changes in the global BC aerosol distribution due to human activity. However, little is known regarding BC's atmospheric distribution or...
Article
Full-text available
Estimation of correlation with appropriate uncertainty limits for scientific data that are potentially serially correlated is a common problem made seriously challenging especially when data are sampled unevenly in space and/or time. Here we present a new, robust method for estimating correlation with uncertainty limits between autocorrelated serie...
Article
Full-text available
A 120 m ice core was drilled on Mill Island, East Antarctica (65°30’ S, 100°40’ E) during the 2009/2010 Australian Antarctic field season. Contiguous discrete 5 cm samples were measured for hydrogen peroxide, water stable isotopes and trace ion chemistry. The ice core was annually dated using a combination of chemical species and water stable isoto...
Conference Paper
Comparison of meteorological records and ice core snowfall data from Law Dome, Antarctica, have previously revealed a teleconnection with drought in southwest Western Australia (van Ommen and Morgan, 2010). Here we extend the comparison period using more recent ice core data (Roberts et al., 2015) that provides a significantly longer overlap with m...
Conference Paper
ICECAP II is a US/Australia/French/Italian collaboration focused on extending coverage of East Antarctic grounding zones and ice shelves as well as searching for sites of million year old ice in the interior of the East Antarctic ice sheet. In January 2016, the ICECAP II project conducted four high resolution survey flights over a region 40 km x 10...
Conference Paper
Full-text available
The Totten Glacier is the outlet for one of the most voluminous catchments in East Antarctica, and shows signs of vulnerability to change. The upstream portions of this catchment include the topographic lows of the Sabrina Subglacial Basin (SSB) and the Aurora Subglacial Basin (ASB), which are surrounded by highland regions. The SSB and ASB each ar...
Article
Full-text available
A high resolution (1 km line spacing) aerogeophysical survey was conducted over a region near the East Antarctic Ice Sheet's Dome C that may hold a 1.5 million year old climate record. New ice thickness data derived from an airborne coherent radar sounder was combined with unpublished data that was unavailable for earlier compilations. We find unde...
Conference Paper
The Totten Glacier is the primary outlet of the Aurora Subglacial Basin (ASB), draining at least 3.5 m of eustatic sea-level potential into the Sabrina Coast alongside the Moscow University Ice Shelf. Recent work has shown that the ASB has drained and filled many times since large-scale glaciation began, including evidence that it collapsed during...
Article
Full-text available
Ice cores provide some of the best-dated and most comprehensive proxy records, as they yield a vast and growing array of proxy indicators. Selecting a site for ice core drilling is nonetheless challenging, as the assessment of potential new sites needs to consider a variety of factors. Here, we demonstrate a systematic approach to site selection fo...
Conference Paper
Full-text available
Understanding the long term trends in sea ice coverage is important, particularly in the context of recent reports of increases in Antarctic sea ice extent. Prior to the satellite era, ice core records have been used as a proxy for past sea ice extent in Antarctica, allowing investigations of the natural variability of Antarctic sea ice extent. The...
Conference Paper
During the last deglaciation (21,000 to 7,000years ago) global sea level rise was punctuated by several abrupt meltwater spikes triggered by the retreat of ice sheets and glaciers worldwide. However, the debate regarding the relative timing, geographical source and the physical mechanisms driving these rapid increases in sea level has catalyzed deb...
Conference Paper
Contiguous measurements of water stable isotope ratios (δ18O and δD) have been performed along the entire length of the Aurora Basin North (ABN) ice core. The 303 m ice core extracted at ABN, 550 km inland of Australia’s Casey station, provides a climate record at seasonal to decadal resolution for this region of East Antarctica spanning the past ~...
Conference Paper
Wind activity across open water of the Southern Ocean is the dominant source for sea-salts at Law Dome. Links between the sub-annual sea-salt record and wind-driven climate patterns have been previously demonstrated with ENSO and IPO signals found in the summer record and the Southern Annular Mode (SAM) and strength of the Antarctic High in the win...
Conference Paper
Ice sheets provide exceptional archives of past changes in polar climate, regional environment and global atmospheric composition. The oldest deep ice drilled in Antarctica has been retrieved at EPICA Dome C (Antarctica), reaching 800,000 years. Retrieving an older paleoclimatic record from Antarctica is one of the biggest challenges of the ice cor...
Conference Paper
Antarctic ice cores, especially those from East Antarctica, are limited in quantity and spatial coverage. Mill Island (65°30’ S, 100°40’ E) is one of the most northerly ice coring sites in East Antarctica, and is located in a region with sparse ice core data. With high snow accumulation at the site (1.35 mIE/yr), the Mill Island ice core enables a...
Conference Paper
Computing correlation between data-series is a ubiquitous method in the geosciences and elsewhere, which is especially useful when accompanied with confidence intervals that take into account the auto-correlation in the data-series themselves. However, not all data series are evenly sampled, either because of inherent non-uniform sampling or becaus...
Conference Paper
This paper presents an overview of work undertaken over a number of Australian Antarctic Science projects, beginning in season 2001/02 with a shallow snow pit. In season 2005/06 this was augmented with a 260 m thermally drilled ice core and a 4.5 m snow pit. A core taken in 2008/09 overlapped the 2005/06 core and pit samples. From 2009/10, short co...
Conference Paper
Extending our record of greenhouse gases beyond the transition into the mid-Pliocene may be key for understanding large scale climate forcing in a higher CO2 world. Finding stratigraphically intact ice older than 800 kyrs will be challenging, requiring finding the sweet spot of stable ice dynamics, low accumulation, smooth bed and low geothermal he...
Conference Paper
Ice cores provide an important means to estimate sulfate aerosol loadings for past volcanic events, and hence to estimate the climate forcing of these events. Snow deposition is influenced by the physical characteristics of the site, including local and regional atmospheric circulation patterns and the relative importance of deposition with precipi...
Conference Paper
We present a new age model for the Dome Summit South (DSS) ice core from Law Dome, East Antarctica. This new model augments the annually dated upper section of the existing ice-core chronology with a calculated age model that is constrained by 11 age ties. Here, we use a continuous piece-wise fit to a linear vertical velocity profile. Specifically,...
Conference Paper
Selecting the best site for ice core drilling is essential, as retrieving a new ice core record is logistically challenging, time consuming and expensive. Assessments of new sites need to consider a variety of factors encompassing all of these concerns. With this in mind, we demonstrate a systematic approach to site selection for a new East Antarct...
Conference Paper
Rainfall in Australia exhibits high multi-decadal variability, yet the short (~100 years) instrumental record and dearth of high resolution proxy records from many regions of the country hinders a full understanding of the features and climatic drivers of this high variability. Subsequently, statistics calculated from the instrumental record do not...
Conference Paper
In Antarctica, a reasonable coverage of ice core records exist for the last couple of hundred years, however there is poor spatial coverage of high-resolution climate data from Antarctica, particularly over the last 2000 years, which is articulated in IPCC synthesis reports as limiting present understanding of climate processes. Two thousand years...
Conference Paper
Full-text available
Annually dated records of snow accumulation rates in Antarctica are essential for estimating ice sheet mass balance and subsequent sea level change. Accumulation rates at Law Dome, East Antarctica, have been linked with regional atmospheric circulation to the midlatitudes as well as regional Antarctic snowfall. Here, we extend the existing 750 year...
Article
Full-text available
Ice cores provide some of the best dated and most comprehensive proxy records, as they yield a vast and growing array of proxy indicators. Selecting a site for ice core drilling is nonetheless challenging, as the assessment of potential new sites needs to consider a variety of factors. Here, we demonstrate a systematic approach to site selection fo...
Conference Paper
Full-text available
As we consider the future on a warming planet, one of our most powerful tools for understanding the long-term climate and earth system responses comes from the record of past climate laid down in various archives. Ice cores from Greenland and Antarctica have delivered remarkable insights into planetary processes through ice age cycles over the last...
Article
Full-text available
Antarctic ice cores have been used to study the history of black carbon (BC), but little is known with regards to the physical and chemical characteristics of these particles in the remote atmosphere. Characterization remains limited by ultra-trace concentrations in ice core samples and the lack of adequate methods to isolate the particles unaltere...
Article
Full-text available
Antarctic ice cores have been used to study the history of black carbon (BC), but little is known with regards to the physical and chemical characteristics of these particles in the remote atmosphere. Characterization remains limited by ultra-trace concentrations in ice core samples and the lack of adequate methods to isolate the particles unaltere...
Conference Paper
Totten Glacier is the primary outlet of the Aurora Subglacial Basin (ASB), draining 3.5 m of eustatic sea-level potential into the Sabrina coast alongside the Moscow University Ice Shelf that fringes the coastline. Recent work has shown that the ASB has drained and filled many times since large-scale glaciation began including evidence that it coll...
Article
Future changes in atmospheric circulation and associated modes of variability are a major source of uncertainty in climate projections. Nowhere is this issue more acute than across the mid-to high-latitudes of the Southern Hemisphere (SH) which over the last few decades has experienced extreme and regional variable trends in precipitation, ocean ci...