Modeling Global Sea Ice with a Thickness and Enthalpy Distribution Model in Generalized Curvilinear Coordinates

Abstract

A parallel ocean and ice model (POIM) in generalized orthogonal curvilinear coordinates has been developed for global climate studies. The POIM couples the Parallel Ocean Program (POP) with a 12-category thickness and enthalpy distribution (TED) sea ice model. Although the POIM aims at modeling the global ocean and sea ice system, the focus of this study is on the presentation, implementation, and evaluation of the TED sea ice model in a generalized coordinate system. The TED sea ice model is a dynamic thermodynamic model that also explicitly simulates sea ice ridging. Using a viscous plastic rheology, the TED model is formulated such that all the metric terms in generalized curvilinear coordinates are retained. Following the POP's structure for parallel computation, the TED model is designed to be run on a variety of computer architectures: parallel, serial, or vector. When run on a computer cluster with 10 parallel processors, the parallel performance of the POIM is close to that of a corresponding POP ocean-only model. Model results show that the POIM captures the major features of sea ice motion, concentration, extent, and thickness in both polar oceans. The results are in reasonably good agreement with buoy observations of ice motion, satellite observations of ice extent, and submarine observations of ice thickness. The model biases are within 8% in Arctic ice motion, within 9% in Arctic ice thickness, and within 14% in ice extent in both hemispheres. The model captures 56% of the variance of ice thickness along the 1993 submarine track in the Arctic. The simulated ridged ice has various thicknesses, up to 20 m in the Arctic and 16 m in the Southern Ocean. Most of the simulated ice is 1-3 m thick in the Arctic and 1-2 m thick in the Southern Ocean. The results indicate that, in the Atlantic-Indian sector of the Southern Ocean, the oceanic heating, mainly due to convective mixing, can readily exceed the atmospheric cooling at the surface in midwinter, thus forming a polynya. The results also indicate that the West Spitzbergen Current is likely to bring considerable oceanic heat (generated by lateral advection and vertical convection) to the Odden ice area in the Greenland Sea, an important factor for an often tongue-shaped ice concentration in that area.

Evaluation of Seven Different Atmospheric Reanalysis Products in the Arctic*

“…Sea ice volume for the entire Arctic is calculated using PIOMAS (Zhang and Rothrock 2003). To allow us to assess the full impact of different forcing datasets, data assimilation in PIOMAS is turned off for this study.…”

“…Reanalysis datasets are used to provide surface atmospheric variables to link the historic state of the atmosphere to the dynamically evolving ice-ocean state in the model. A notable application of this class of models is the production of retrospective time series of sea ice thickness and volume (e.g., Zhang and Rothrock 2003;Hunke and Holland 2007;Lindsay et al 2009;Schweiger at al. 2011;Notz et al 2013).…”

Arctic sea-ice diffusion from observed and simulated Lagrangian trajectories

“…The model is initialized with the ice concentration derived from the AMSR-E passive microwave sensor (Kaleschke et al, 2001;Spreen et al, 2008, data obtained from the Integrated Climate Date Center, University of Hamburg, Germany, http://icdc.zmaw.de) and the TOPAZ reanalysis ice thickness, within the area covered with ice. As the modeled ice volume of the TOPAZ reanalysis is known to be too low (Sakov et al, 2015), we increased the initial thickness uniformly so that the total volume is the same as that given by the PIOMAS model (Zhang and Rothrock, 2003) on 15 The neXtSIM model is able to simulate correctly the observed evolution of the sea-ice volume, extent and area for the freezing season (from September to May) but simulates a too-rapid melt from May onwards . This limitation does not impact the results of this study as we only analyze simulated drift in winter with simulations restarted every September.…”

Arctic Ocean Circulation Patterns Revealed by GRACE

“…PIOMAS is a regional ice-ocean model with 30 vertical levels and spatial resolution better than 22 km (Zhang and Rothrock 2003). The ''North Pole'' of the PIOMAS model is located in northern Greenland, with the goal of maximizing the resolution of flow exchange in the region of Fram Strait.…”