PHC: A Global Ocean Hydrography with a High-Quality Arctic Ocean

Steele, Michael; Morley, Rebecca; Ermold, Wendy

doi:10.1175/1520-0442(2001)014<2079:pagohw>2.0.co;2

Cited by 921 publications

(780 citation statements)

References 13 publications

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“…Both models also overestimate the ocean mixed-layer depth in the Arctic. Annual mean mixed-layer depth based on observational data (Steele et al 2001) is 35.6 m while that of MIROC4m and MIROC5 is 76.4 and 151.8 m, respectively [the details of this issue are investigated in Komuro (2014)]. A much larger annual range of mixed-layer depth in MIROC5 than MIROC4m may affect the seasonal energy exchange between the atmosphere and ocean, which requires further study.…”

Section: Discussionmentioning

confidence: 99%

Robust Seasonality of Arctic Warming Processes in Two Different Versions of the MIROC GCM

et al. 2014

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It is one of the most robust projected responses of climate models to the increase of atmospheric CO 2 concentration that the Arctic experiences a rapid warming with a magnitude larger than the rest of the world. While many processes are proposed as important, the relative contribution of individual processes to the Arctic warming is not often investigated systematically. Feedbacks are quantified in two different versions of an atmosphere-ocean GCM under idealized transient experiments based on an energy balance analysis that extends from the surface to the top of the atmosphere. The emphasis is placed on the largest warming from late autumn to early winter (October-December) and the difference from other seasons. It is confirmed that dominating processes vary with season. In autumn, the largest contribution to the Arctic surface warming is made by a reduction of ocean heat storage and cloud radiative feedback. In the annual mean, on the other hand, it is the albedo feedback that contributes the most, with increasing ocean heat uptake to the deeper layers working as a negative feedback. While the qualitative results are robust between the two models, they differ quantitatively, indicating the need for further constraint on each process. Ocean heat uptake, lower tropospheric stability, and low-level cloud response probably require special attention.

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Section: Discussionmentioning

confidence: 99%

Robust Seasonality of Arctic Warming Processes in Two Different Versions of the MIROC GCM

et al. 2014

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“…The model is initialised in 1973 using climatology that combines the World Atlas of 2005 (WOA05, Locarnini et al, 2006;Antonov et al, 2006) with version 3.0 of the Polar Science Center Hydrographic Climatology (PHC, Steele et al, 2001). At the lateral boundaries, model fields are relaxed towards the same monthly climatology, with the relaxation zone width of 20 grid cells and an e-folding time of 30 day MLD/15 m. The model includes an additional barotropic inflow of 0.7 Sv through the Bering Strait, representing the inflow of Pacific Water.…”

Section: The Modelmentioning

confidence: 99%

TOPAZ4: an ocean-sea ice data assimilation system for the North Atlantic and Arctic

et al. 2012

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Abstract. We present a detailed description of TOPAZ4, the latest version of TOPAZ -a coupled ocean-sea ice data assimilation system for the North Atlantic Ocean and Arctic. It is the only operational, large-scale ocean data assimilation system that uses the ensemble Kalman filter. This means that TOPAZ features a time-evolving, state-dependent estimate of the state error covariance. Based on results from the pilot MyOcean reanalysis for 2003-2008, we demonstrate that TOPAZ4 produces a realistic estimate of the ocean circulation in the North Atlantic and the sea-ice variability in the Arctic. We find that the ensemble spread for temperature and sea-level remains fairly constant throughout the reanalysis demonstrating that the data assimilation system is robust to ensemble collapse. Moreover, the ensemble spread for ice concentration is well correlated with the actual errors. This indicates that the ensemble statistics provide reliable state-dependent error estimates -a feature that is unique to ensemble-based data assimilation systems. We demonstrate that the quality of the reanalysis changes when different sea surface temperature products are assimilated, or when in-situ profiles below the ice in the Arctic Ocean are assimilated. We find that data assimilation improves the match to independent observations compared to a free model. Improvements are particularly noticeable for ice thickness, salinity in the Arctic, and temperature in the Fram Strait, but not for transport estimates or underwater temperature. At the same time, the pilot reanalysis has revealed several flaws in the system that have degraded its performance. Finally, we show that a simple bias estimation scheme can effectively detect the seasonal or constant bias in temperature and sea-level.

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“…the area south of 60 • N, north of 70 • N, west of 30 • W and east of 5 • W, are restored to the climatologic fields of the PHC 3.0 (Polar Science Center Hydrographic Climatology) data set (Steele et al, 2001). This data set, compiled in 2005, combines the "Word Ocean Atlas" (1998 edition), the "Arctic Ocean Atlas" and selected Canadian data provided form the Bedford Institute of Oceanography and therefore forms an appropriate resource for the simulation of the North Atlantic/Arctic Ocean (Li et al, 2011).…”

Section: Data Assimilationmentioning

confidence: 99%

The circulation of Icelandic waters – a modelling study

et al. 2013

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Abstract. The three-dimensional flow, temperature and salinity fields of the North Atlantic, including the Arctic Ocean, covering the time period 1992 to 2006 are simulated with the numerical ocean model CODE. The simulation reveals several new insights and previously unknown structures which help us to clarify open questions on the regional oceanography of Icelandic waters. These relate to the structure and geographical distribution of the coastal current, the primary forcing of the North Icelandic Irminger Current (NIIC) and the path of the Atlantic Water south-east of Iceland. The model's adaptively refined computational mesh has a maximum resolution of 1 km horizontal and 2.5 m vertical in Icelandic waters. CTD profiles from this region and the river discharge of 46 Icelandic watersheds, computed by the hydrological model WaSiM, are assimilated into the simulation. The model realistically reproduces the established elements of the circulation around Iceland. However, analysis of the simulated mean flow field also provides further insights. It suggests a distinct freshwater-induced coastal current that only exists along the south-west and west coasts, which is accompanied by a counter-directed undercurrent. The simulated transport of Atlantic Water over the Icelandic shelf takes place in a symmetrical system of two currents, with the established NIIC over the north-western and northern shelf, and a hitherto unnamed current over the southern and southeastern shelf, which is simulated to be an upstream precursor of the Faroe Current (FC). Both currents are driven by barotropic pressure gradients induced by a sea level slope across the Greenland-Scotland Ridge. The recently discovered North Icelandic Jet (NIJ) also features in the model predictions and is found to be forced by the baroclinic pressure field of the Arctic Front, to originate east of the Kolbeinsey Ridge and to have a volume transport of around 1.5 Sv within northern Denmark Strait. The simulated multi-annual mean Atlantic Water transport of the NIIC increased by 85 % during 1992 to 2006, whereas the corresponding NIJ transport decreased by 27 %. Based on our model results we propose a new and further differentiated circulation scheme of Icelandic waters whose details may inspire future observational oceanography studies.

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PHC: A Global Ocean Hydrography with a High-Quality Arctic Ocean

Cited by 921 publications

References 13 publications

Robust Seasonality of Arctic Warming Processes in Two Different Versions of the MIROC GCM

Robust Seasonality of Arctic Warming Processes in Two Different Versions of the MIROC GCM

TOPAZ4: an ocean-sea ice data assimilation system for the North Atlantic and Arctic

The circulation of Icelandic waters – a modelling study

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