Fraser Davidson

Reconstruction of environmental histories to investigate patterns of larval radiated shanny ( Ulvaria subbifurcata ) growth and selective survival in a large bay of Newfoundland

We used otolith microstructure analysis to reconstruct the growth histories of larval radiated shanny ( Ulvaria subbifurcata ) collected over a 2-week period in Trinity Bay, Newfoundland. A dynamic 3-dimensional, eddy-resolving circulation model of the region provided larval drift patterns, which were combined with measurements of temperature and zooplankton abundance to assess the environmental history of the larvae. The abundance of juvenile and adult capelin ( Mallotus villosus ), the dominant planktivorous fish in this area, was monitored using five hydroacoustic surveys. The goal was to determine whether environmental histories are helpful in explaining spatial and temporal differences in larval shanny growth, measured as cumulative distribution functions (CDF) of growth rates. We found evidence for a selective loss of slower growing individuals and recognized considerable spatial differences in the CDF of larval growth rates. Consistent patterns in capelin abundance suggested that faster growing survivors, sampled at the end of the 2-week period, developed in areas of low predator densities. A dome-shaped relationship between temperature and larval growth was observed, explaining a significant but small amount of the overall variability (14%). Effects of experienced prey concentrations on larval growth rates could not be demonstrated.

Status and future of global and regional ocean prediction systems

Operational evolution of global and regional ocean forecasting systems has been extremely significant in recent years. Global Ocean Data Assimilation Experiment (GODAE) Oceanview supports the national research groups providing them with coordination and sharing expertise among the partners. Several systems have been set up and developed pre-operationally, and the majority of these are now fully operational; at the present time, they provide medium- and long-term forecasts of the most relevant ocean physical variables. These systems are based on ocean general circulation models and data-assimilation techniques that are able to correct the model with the information inferred from different types of observations. A few systems also incorporate a biogeochemical component coupled with the physical system, while others are based on coupled ocean–wave–ice–atmosphere models. The products are routinely validated with observations in order to assess their quality. Data and product implementation and organization, as well as service, for users have been well tried and tested, and most of the products are now available to users. The interaction with different users is an important factor in the development process. This paper provides a synthetic overview of the GODAE OceanView prediction systems.

GODAE OceanView Class 4 forecast verification framework: global ocean inter-comparison

As part of the work of the GODAE OceanView Inter-comparison and Validation Task Team (IV-TT), 6 global ocean forecasting systems spread across 5 operational oceanography forecast centres were inter-compared using a common set of observations as a proxy for the truth. The ‘Class 4’ in the title refers to a set of forecast verification metrics defined in the MERSEA-IP/GODAE internal metrics document (Hernandez 2007), the defining feature of which is that comparisons between forecasts and observations take place in observation space. This approach is seen as a departure from other diagnostic approaches such as analysing model trends or innovation statistics, and is commonly used in the atmospheric community. The physical parameters involved in the comparison are sea surface temperature (SST), sub-surface temperature, sub-surface salinity and sea level anomaly (SLA). SST was measured using in-situ observations obtained from USGODAE, sub-surface conditions were compared to Argo profiles, while sea level anomaly was measured by several satellite altimeters courtesy of AVISO. The 5 forecast centres involved in the project were Met Office, Australian Bureau of Meteorology, Mercator Océan, Environment Canada and NOAA/NWS/NCEP. Combining Met Office, Mercator Océan and Environment Canada forecasts into a mixed resolution multi-model ensemble produces estimates of the ocean state which have better accuracy and associativity properties for SST, SLA and temperature profiles than any individual ensemble component.

Recent progress in performance evaluations and near real-time assessment of operational ocean products

Operational ocean forecast systems provide routine marine products to an ever-widening community of users and stakeholders. The majority of users need information about the quality and reliability of the products to exploit them fully. Hence, forecast centres have been developing improved methods for evaluating and communicating the quality of their products. Global Ocean Data Assimilation Experiment (GODAE) OceanView, along with the Copernicus European Marine Core Service and other national and international programmes, has facilitated the development of coordinated validation activities among these centres. New metrics, assessing a wider range of ocean parameters, have been defined and implemented in real-time. An overview of recent progress and emerging international standards is presented here.

Arctic sea ice and freshwater sensitivity to the treatment of the atmosphere‐ice‐ocean surface layer

Global simulations are presented focusing on the atmosphere-ice-ocean (AIO) surface layer (SL) in the Arctic. Results are produced using an ocean model (NEMO) coupled to two different sea ice models: the Louvain-La-Neuve single-category model (LIM2) and the Los Alamos multicategory model (CICE4). A more objective way to adjust the sea ice-ocean drag is proposed compared to a coefficient tuning approach. The air-ice drag is also adjusted to be more consistent with the atmospheric forcing data set. Improving the AIO SL treatment leads to more realistic results, having a significant impact on the sea ice volume trend, sea ice thickness, and the Arctic freshwater (FW) budget. The physical mechanisms explaining this sensitivity are studied. Improved sea ice drift speeds result in less sea ice accumulation in the Beaufort Sea, correcting a typical ice thickness bias. Sea ice thickness and drag parameters affect how atmospheric stress is transferred to the ocean, thereby influencing Ekman transport and FW retention in the Beaufort Gyre (BG). Increasing sea ice-ocean roughness reduces sea ice growth in winter by reducing ice deformation and lead fractions in the BG. It also increases the total Arctic FW content by reducing sea ice export through Fram Strait. Similarly, increasing air-ice roughness increases the total Arctic FW content by increasing FW retention in the BG.

GODAE OceanView Inter-comparison for the Australian Region

This paper compares the performance of short-range operational ocean forecasts, using ‘observational space’ metrics developed under GODAE OceanView (GOV). Best estimates (behind the real-time analysis) and forecasts are inter-compared for the Australian region (0-50S, 90-180E) for 2013. Systems considered include those developed in Australia, France, Canada, United Kingdom and USA. Each system is compared to observations of along-track sea level anomaly, sea surface temperature observations from surface drifters and sub-surface Argo profiles of temperature and salinity. The UK operational system generally has the smallest errors for sea surface temperature and sea level anomaly for the Australian region. However, the French systems outperform others in sub-surface temperature and salinity for the region. Of the two products provided by the Australian centre, an ensemble based approach is found to perform better than the deterministic system, having higher skill and lower root mean square errors. Some of the ‘better’ results of systems can be attributed in part to the lack of independence of the reference observations; however the study does demonstrate the feasibility and robustness of GOV global ocean inter-comparison efforts for regional applications.

Seasonal variability of the warm Atlantic Water layer in the vicinity of the Greenland shelf break

The warmest water reaching the east and west coast of Greenland is found between 200?m and 600?m. Whilst important for melting Greenlands outlet glaciers, limited winter observations of this layer prohibit determination of its seasonality. To address this, temperature data from Argo profiling floats, a range of sources within the World Ocean Database and unprecedented coverage from marine-mammal borne sensors have been analysed for the period 2002-2011. A significant seasonal range in temperature (~1-2?°C) is found in the warm layer, in contrast to most of the surrounding ocean. The phase of the seasonal cycle exhibits considerable spatial variability, with the warmest water found near the eastern and southwestern shelf-break towards the end of the calendar year. High-resolution ocean model trajectory analysis suggest the timing of the arrival of the years warmest water is a function of advection time from the subduction site in the Irminger Basin.

A Canadian contribution to an integrated Atlantic ocean observing system (IAOOS)

We review opportunities, impediments, regional scope and principles for a Canadian contribution to an Integrated Atlantic Ocean Observing System (IAOOS) in the context of the Galway Alliance. This contribution should build on what exists, plan ahead for data management and data access, be flexible and sustainable, encourage international involvement, be science-led, foster research aggregation, and have close links to remote sensing, data assimilation and prediction programs. Existing programs that can contribute are described, and new initiatives that will broaden relevance of the Observing System are identified, including biological/ ecosystem observations. Specific platforms and technologies for both near-shore and offshore waters are listed, together with areas where new developments are needed. Finally, we outline a strategy for the development of an Atlantic Canada Regional Ocean Observing System (ACROOS).