Antarctic and Southern Ocean Sea-Ice and Climate Trends

Jacka, T. H.

doi:10.3189/s0260305500008417

Cited by 19 publications

(9 citation statements)

References 18 publications

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“…The reconstructed temperature history can be compared with other records of past climate over East Antarctica. The most recent history, the last 50 years, can be compared with direct observations (Jones and Wigley, 1988; Jacka, 1990; Jones, 1990; Morgan and others, 1991). The observed warming over the last 30 years (Jacka, 1990) is seen in the reconstructed temperature history as a 0.75 K rise.…”

Section: Discussionmentioning

confidence: 99%

“…The most recent history, the last 50 years, can be compared with direct observations (Jones and Wigley, 1988; Jacka, 1990; Jones, 1990; Morgan and others, 1991). The observed warming over the last 30 years (Jacka, 1990) is seen in the reconstructed temperature history as a 0.75 K rise. This is in agreement with an Antarctic average temperature increase of 0.5 K over these 30 years (Jacka, 1990; Peel, 1992; King and Turner, 1997).…”

Section: Discussionmentioning

confidence: 99%

“…The observed warming over the last 30 years (Jacka, 1990) is seen in the reconstructed temperature history as a 0.75 K rise. This is in agreement with an Antarctic average temperature increase of 0.5 K over these 30 years (Jacka, 1990; Peel, 1992; King and Turner, 1997). The data from Casey station, close to the drill site, support the 0.75 K increase in the Law Dome region (Van Ommen and others, 1999).…”

Section: Discussionmentioning

confidence: 99%

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Monte Carlo inverse modelling of the Law Dome (Antarctica) temperature profile

1999

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ABSTRACT. The temperature profile in the 1200 m deep Dome Summit South (DSS) borehole near the summit of Law Dome, Antarctica, was measured in 1996, 3 years after the termination of the deep drilling.The temperature profile contains information on past surface temperature over the last 4 ka. This temperature history is determined by the use of a Monte Carlo inverse method in which no constraints are placed on the unknown temperature history and no solution is assumed to be unique. The temperature history is obtained from a selection of equally well-fitting solutions by a statistical treatment.The results show that solutions covering the last 4 ka have a well-developed central value, a most likely temperature history. The temperature record has two well-developed minima at AD1250 and 1850. From 1850 to the present, temperatures have gradually increased by 0.7 K. The reconstructed temperatures are compared with the stable oxygen isotope ( IV y) from the DSS ice core. TEMPERATURE PROFILE FROM LAW DOMEIn 1993 the glaciology group of the Australian Antarctic Division completed the drilling of a 1200 m deep ice core to bedrock 4.68 km south-southwest of the highest point on the Law Dome ice cap (66³46 H S,112³48 H E;1370 m a.s.l.) (Morgan and others, 1997). In 1996 a temperature profile was inferred from measurements every 10^20 m in the deep borehole, with a measuring accuracy of 0.02 K (Van Ommen and others, 1999). Temperature measurements in the top 50 m are from the cased part of the deep borehole, above the liquid level, and they are disturbed and influenced by the temperature and pressure conditions in the building constructed over the borehole. They do not represent the undisturbed firn and ice temperatures.In 1997, temperatures were measured in a 270 m deep dry borehole drilled 80 m south of the deep borehole (Van Ommen and others, 1999). These temperatures have an accuracy of 0.05 K, but are believed to be a better representation of the undisturbed firn and ice temperatures than those from shallow depths in the deep borehole. The two temperature profiles were combined in such a way that the shallow borehole profile was used down to 50 m, the depth zone between 50 and 270 m was used to align the two profiles, and the temperatures from the deep borehole were used below 50 m. The combined temperature profile (Fig. 1a, solid curve) is used to reconstruct the past temperature history. A study of the noise in the data (Fig. 1b) clearly shows the increased errors in the measurements from the shallow borehole. Below 750 m depth, convection cells in the borehole liquid are seen to appear. Temperature excursions in the profile due to these cells increase as the temperature gradient increases (Gundestrup, 1989; Gundestrup and others, 1994; Gundestrup and Clow, 1997).The convection cells are smoothed out before the reconstruction of the past temperatures is attempted, as they do not represent ice temperatures.A temperature profile assuming steady-state conditions and the present-day ice-sheet configuration (accumula...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Monte Carlo inverse modelling of the Law Dome (Antarctica) temperature profile

1999

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“…One of these is both south and north of the December edge in the ice embayment shown as being formed by the westward retreat of the sea ice into the South Atlantic sector. When compared with the modern satellite data from Jacka (1990), the distance between the December and January ice edge on the Mackintosh (1972) charts is too small by 3° of latitude at 45°E and by about 1° at 35°E, 55°E, and 65°E. Assuming that the amplitude of the seaice retreat is no less in the pre-1959 period than post-1972 indicates that these three de la Mare January ice-edge positions would be south of the likely December line.…”

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confidence: 88%

Whaling records and changes in Antarctic sea ice: consistency with historical records

Mare

2002

Polar Record

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A claim that there are substantial discrepancies between direct observations of the Antarctic sea-ice edge and the implicit sea-ice edge derived from whaling records is rebutted. The claimeddiscrepancies are shown to arise largely from comparing the two types of information from different dates. A date-corrected comparison shows generally good agreement between the southernmost limit of whaling and the most comprehensive of the early monthly ice charts of Antarctica. The remaining apparent discrepancies are accounted for either by very limited data or the complex nature of the ice edge in the region of the Weddell ice tongue. Correlation of the southernmost limits of whaling with direct observations of the ice edge provides the most powerful calibration of the relationship between them

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“…Over the past several decades, local precipitation or surface-air temperature increases have been recorded at a number of Antarctic sites (Pourchct and others, 1983; Peel and Mulvancy, 1988; Jacka, 1990; Jones, 1990; Morgan and others, 1991; Weatherly and others, 1991). The Vostok ice-core data suggest substantially lower snow accumulation on Antarctica during the last glacial maximum (Lorius and others, 1989), and initial satellite-altimeter analyses arc suggestive of recent regional elevation increases (Partington and others, 1991).…”

Section: Temporal Variabilitymentioning

confidence: 99%

Melting of ice shelves and the mass balance of Antarctica

et al. 1992

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ABSTRACT. We calculate the present ice budget for Antarctica from measurements of accumulation minus iceberg calving, run-ofT and in situ meltin~ beneath the floating ice shelves . The resulting negative mass balance of 469 Gt yeardifTers substantially from other recent estimates but some components are subject to high temporal variability and budget uncertainties of20-50%. Annual accumulation from an earlier review is adjusted to include the Antarctic Peninsula for a total of 2144Gtyear-l . An iceberg production rate of 2016 Gtyear-I is obtained from the volume of large icebergs calculated from satellite images since 1978, and from the results of an international iceberg census project. Ice-shelf melting of 544 Gt year-I is derived from physical and geochemical observations of meltwater outflow, glaciological field studies and modeling of the sub-ice ocean circulation. The highest melt rates occur near ice fronts and deep within sub-ice cavities. Run-ofT from the ice-sheet surface and from beneath the grounded ice is taken to be 53 Gt year-I. Less than half of the negative mass balance need come from the grounded ice to account for the unattributed 0.45 mm year-I in the IPCC "best estimate" of the recent global sea-level rise.

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Antarctic and Southern Ocean Sea-Ice and Climate Trends

Cited by 19 publications

References 18 publications

Monte Carlo inverse modelling of the Law Dome (Antarctica) temperature profile

Monte Carlo inverse modelling of the Law Dome (Antarctica) temperature profile

Whaling records and changes in Antarctic sea ice: consistency with historical records

Melting of ice shelves and the mass balance of Antarctica

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