Polynya Dynamics: a Review of Observations and Modeling

Maqueda, M. A. Morales; Willmott, Andrew J.; Biggs, N. R. T.

doi:10.1029/2002rg000116

Cited by 304 publications

(331 citation statements)

References 247 publications

(400 reference statements)

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“…The polynya reaches its maximum extent during the first cycle with about 53,000 km 2 . This area is in agreement with the winter maximum reported by Maqueda et al [2004] for the same polynya. During the second cycle the polynya reaches a relative maximum of about 30,000 km 2 .…”

Section: Ross Sea: Large Scalesupporting

confidence: 92%

“…The majority of the studies of TNB polynya focus on polynya size and the relationship of polynya size with the occurrence of katabatic winds. There are only few studies that give sea ice production estimates and none of these estimates are based directly on sea ice observations [Maqueda et al, 2004]. Kurtz and Bromwich [1985] used atmospheric climatology data to calculate a sea ice production rate of 49.4 km 3 in the months from May to August.…”

Section: Introductionmentioning

confidence: 99%

“…[3] TNB katabatic winds have been widely studied through model simulations and observations [Maqueda et al, 2004]. The majority of the studies of TNB polynya focus on polynya size and the relationship of polynya size with the occurrence of katabatic winds.…”

Section: Introductionmentioning

confidence: 99%

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The sea ice dynamics of Terra Nova Bay and Ross Ice Shelf Polynyas during a spring and winter simulation

2008

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[1] The Terra Nova Bay (TNB) and Ross Ice Shelf (RIS) polynyas are simulated using a coupled atmosphere-sea ice model in winter 2002 and summer 2000. The atmospheric component of the model is compared with Automatic Weather Stations (AWS) data and shows a significantly increased skill over the ECMWF atmospheric variables. During winter, the sea ice production in TNB is largely determined by katabatic winds. We estimate the monthly production rate to be 8.7 km 3 /month of sea ice during winter. In early summer (November), the katabatics are weaker and the sea ice production is more influenced by the synoptic wind. The net sea ice production is weaker during November at 1.2 km 3 /month. The summer production is characterized by a diurnal cycle of melt and sea ice formation. For small coastal polynyas, like TNB, it is important to resolve all the glacier valleys accurately. Increasing the model resolution by a factor of five leads to a doubling of the sea ice formation during winter simulations due to the point intensity of the katabatics winds. For open coastal polynyas, like RIS polynya, sea ice production is largely controlled by synoptic winds and resolution is less important. The RIS polynya production is 61.3 km 3 during winter and 19.1 km 3 during November. These results are comparable to RIS polynya observations. Although the TNB polynya has a smaller winter sea ice production, the sea ice rate of growth per unit area is 1.6 times that of the RIS polynya.

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Section: Ross Sea: Large Scalesupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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The sea ice dynamics of Terra Nova Bay and Ross Ice Shelf Polynyas during a spring and winter simulation

2008

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“…Today, Antarctic coastal polynyas are very important areas for AABW production and therefore also contribute to the overturning circulation in the oceans (Morales Maqueda et al, 2004). Offshore blowing katabatic winds remove sea ice from coastal areas or the shelf-ice edge and often lead the development of coastal polynyas (Williams et al, 2007;Kern, 2009).…”

Section: Modern and Lgm Polynyas And Their Relation To Bottom-water Pmentioning

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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“…When the width X is attained, ice production within the thin-ice region of the polynya is balanced by ice export across x = X, namely, X 0 F dx = H X U X , an idea first suggested by Lebedev (1968). Although flux models have proven useful in both theoretical and applied polynya studies (Morales Maqueda, Willmott & Biggs 2004;Willmott et al 2007), the reduced physics invoked by these models lends itself to many criticisms. Prominent among these is the fact that, while flux models conserve mass across the pile-up region, as guaranteed by (1.1), they ignore the conservation of linear momentum, an approach which simplifies the mathematics of the model but can be justified on no grounds other than expediency.…”

mentioning

confidence: 99%

The opening of wind-driven polynyas

2014

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The opening of wind-driven coastal polynyas has often been investigated using idealised flux models. Polynya flux models postulate that the boundary separating the region of thin ice adjacent to the coast within the polynya from the thicker ice piling up downstream is a mathematical shock. To conserve mass, any divergence of the ice flux across the shock translates into a change in the shock's position or, in other words, a change in the width of the thin-ice region of the polynya. Polynya flux models are physically incomplete in that, while they conserve ice mass, they do not conserve linear momentum. In this paper, we investigate the improvements that can be achieved in the simulation of polynyas by imposing conservation of momentum as well as mass. We start by adopting a mathematically solid formulation of the ice mass and momentum balances throughout the polynya region, from the coast to the pack ice. Hydrostatic and plastic versions of the ice internal forces are used in the model. Two different approaches are then explored. We first postulate the existence of a shock at the seaward edge of the thin-ice region of the polynya and derive jump conditions for the conservation of ice mass and momentum at the shock which are consistent with the continuous model physics. Polynyas simulated by this mass-and momentum-conserving shock model always reach a steady state if the polynya forcing is uniform in space and constant in time. This is also true for all polynya flux models presented previously in the literature, but the location of the steady-state polynya edge and the time required to reach it can greatly differ between shock formulations and more simplistic flux ones. We next relax the assumption that a shock exists and let the boundary between thin ice and piling up ice emerge naturally as part of the full solution of the continuous model equations. Polynyas simulated in this way are very different from those simulated by either shock or flux models. Most notably, we find that steady-state polynya solutions are not always attainable in the continuous model. We determine under which conditions this is so and explain how such unsteady solutions come about. We also show that, in those cases when a steady-state solution exists in the continuous model, the steady-state polynya width is considerably larger than in the shock model, and the time required to attain it is accordingly longer. The occurrence of such significant differences between the polynya solutions calculated with flux and shock models, on the one hand, and with more sophisticated continuous † Email address for correspondence: mamm@noc.ac.uk

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Polynya Dynamics: a Review of Observations and Modeling

Cited by 304 publications

References 247 publications

The sea ice dynamics of Terra Nova Bay and Ross Ice Shelf Polynyas during a spring and winter simulation

The sea ice dynamics of Terra Nova Bay and Ross Ice Shelf Polynyas during a spring and winter simulation

Seasonal changes in glacial polynya activity inferred from Weddell Sea varves

The opening of wind-driven polynyas

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