Impact of Atmospheric Forcing on Antarctic Continental Shelf Water Masses

Petty, Alek; Feltham, D. L.; Holland, Paul R.

doi:10.1175/jpo-d-12-0172.1

Cited by 55 publications

(78 citation statements)

References 38 publications

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“…MWDW intrudes onto the shelf and mixes with the ISW to produce WSBW (Foldvik et al, 1985). HSSW is generated during sea-ice production by brine rejection (Foldvik et al, 2004;Petty et al, 2013) and supercooled by circulation under the ice shelf, thereby creating dense and cold ice-shelf water (ISW; Nicholls et al, 2009). Passive tracer experiments also point to the FilchnerRønne Ice Shelf as the main location for bottom-water production (Beckmann et al, 1999).…”

Section: Study Area and Regional Oceanographymentioning

confidence: 99%

Seasonal changes in glacial polynya activity inferred from Weddell Sea varves

et al. 2014

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Abstract. The Weddell Sea and the associated FilchnerRønne Ice Shelf constitute key regions for global bottomwater production today. However, little is known about bottom-water production under different climate and icesheet conditions. Therefore, we studied core PS1795, which consists primarily of fine-grained siliciclastic varves that were deposited on contourite ridges in the southeastern Weddell Sea during the Last Glacial Maximum (LGM). We conducted high-resolution X-ray fluorescence (XRF) analysis and grain-size measurements with the RADIUS tool (Seelos and Sirocko, 2005) using thin sections to characterize the two seasonal components of the varves at sub-mm resolution to distinguish the seasonal components of the varves.Bright layers contain coarser grains that can mainly be identified as quartz in the medium-to-coarse silt grain size. They also contain higher amounts of Si, Zr, Ca, and Sr, as well as more ice-rafted debris (IRD). Dark layers, on the other hand, contain finer particles such as mica and clay minerals from the chlorite and illite groups. In addition, Fe, Ti, Rb, and K are elevated. Based on these findings as well as on previous analyses on neighbouring cores, we propose a model of enhanced thermohaline convection in front of a grounded ice sheet that is supported by seasonally variable coastal polynya activity during the LGM. Accordingly, katabatic (i.e. offshore blowing) winds removed sea ice from the ice edge, leading to coastal polynya formation. We suggest that glacial processes were similar to today with stronger katabatic winds and enhanced coastal polynya activity during the winter season. Under these conditions, lighter coarser-grained layers are likely glacial winter deposits, when brine rejection was increased, leading to enhanced bottom-water formation and increased sediment transport. Vice versa, darker finer-grained layers were then deposited during less windier season, mainly during summer, when coastal polynya activity was likely reduced.

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Section: Study Area and Regional Oceanographymentioning

confidence: 99%

Seasonal changes in glacial polynya activity inferred from Weddell Sea varves

et al. 2014

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“…The smaller ice shelves in the Amundsen Sea are melted by warmer waters. Sea ice growth is less intense in the Amundsen Sea (Petty et al 2013), allowing warm and saline Circumpolar Deep Water at approximately 18C to flood the continental shelf and occupy its ice shelf cavities (Jacobs et al 2012). These ice shelves melt at mean rates of O(10) m yr 21 and hence are much smaller than FRIS, responding to ocean changes on a time scale of only a few months (Heimbach and Losch 2012).…”

Section: Introductionmentioning

confidence: 99%

The Transient Response of Ice Shelf Melting to Ocean Change

Holland

2017

Journal of Physical Oceanography

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Idealized modeling studies have shown that the melting of ice shelves varies as a quadratic function of ocean temperature. However, this result is the equilibrium response, derived from steady ice-ocean simulations subjected to a fixed ocean forcing. This study considers instead the transient response of melting, using unsteady simulations subjected to forcing conditions that are oscillated with a range of periods. The results show that the residence time of water in the subice cavity offers a critical time scale. When the forcing varies slowly (period of oscillation residence time), the cavity is fully flushed with forcing anomalies at all stages of the cycle and melting follows the equilibrium response. When the forcing varies rapidly (period # residence time), multiple cold and warm anomalies coexist in the cavity, cancelling each other in the spatial mean and thus inducing a relatively steady melt rate. This implies that all ice shelves have a maximum frequency of ocean variability that can be manifested in melting. Between these two extremes, an intermediate regime occurs in which melting follows the equilibrium response during the cooling phase of the forcing cycle, but deviates during warming. The results show that ice shelves forced by warm water have high melt rates, high equilibrium sensitivity, and short residence times and hence a short time scale over which the equilibrium sensitivity is manifest. The most rapid melting adjustment is induced by warm anomalies that are also saline. Thus, ice shelves in the Amundsen and Bellingshausen Seas, Antarctica, are highly sensitive to ocean change.

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“…Sensitivity studies of one-dimensional models of sea ice have been used in the past to assess the relative importance of different processes in driving the sea ice response to a prescribed external forcing in the Arctic [19] and in the Antarctic [20]. These approaches are helpful in understanding the mean behaviour of the sea ice system but fail to capture the spatio-temporal complexity of the sea ice response and ignore feedbacks between the atmosphere, ice and ocean.…”

Section: Introductionmentioning

confidence: 99%

Processes controlling surface, bottom and lateral melt of Arctic sea ice in a state of the art sea ice model

Feltham

Petty

Schröder

et al. 2015

Phil. Trans. R. Soc. A.

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We present a modelling study of processes controlling the summer melt of the Arctic sea ice cover. We perform a sensitivity study and focus our interest on the thermodynamics at the ice-atmosphere and iceocean interfaces. We use the Los Alamos community sea ice model CICE, and additionally implement and test three new parametrization schemes: (i) a prognostic mixed layer; (ii) a three equation boundary condition for the salt and heat flux at the ice-ocean interface; and (iii) a new lateral melt parametrization. Recent additions to the CICE model are also tested, including explicit melt ponds, a form drag parametrization and a halodynamic brine drainage scheme. The various sea ice parametrizations tested in this sensitivity study introduce a wide spread in the simulated sea ice characteristics. For each simulation, the total melt is decomposed into its surface, bottom and lateral melt components to assess the processes driving melt and how this varies regionally and temporally. Because this study quantifies the relative importance of several processes in driving the summer melt of sea ice, this work can serve as a guide for future research priorities.

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Impact of Atmospheric Forcing on Antarctic Continental Shelf Water Masses

Cited by 55 publications

References 38 publications

Seasonal changes in glacial polynya activity inferred from Weddell Sea varves

Seasonal changes in glacial polynya activity inferred from Weddell Sea varves

The Transient Response of Ice Shelf Melting to Ocean Change

Processes controlling surface, bottom and lateral melt of Arctic sea ice in a state of the art sea ice model

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