A numerical study of the Southern Ocean including a thermodynamic active ice shelf - Part 1: Weddell Sea

There is a great amount of uncertainty regarding the understanding of the atmosphere-ocean-cryosphere interactions in the Southern Ocean despite the role that the region plays in our changing climate. With the aim of studying the relative importance of sea-ice and ice shelf processes in the Southern Ocean, a coupled ocean circulation sea-ice/ice shelf cavity model based on the Regional Ocean Model System (ROMS) is used in a periodic circumpolar domain with enhanced resolution in the Weddell Sea. A hierarchy of numerical experiments is performed where first a sea-ice model is used and then an ice shelf thermodynamic parameterization is included in order to evaluate the improvements resulting from each component. Results show that it is necessary to consider the formation and melting of sea-ice in order to adequately reproduce the observed hydrography and circulation. Inclusion of ice shelves cavities in the model only improves results if the ice shelf-ocean thermodynamic fluxes are active. Ice shelves and ocean interactions are an important process to be considered in order to obtain realistic hydrographic values under the ice shelf. The model framework presented in this work is a promising tool for analyzing the Southern Ocean response to future climate change scenarios

The impacts of Meltwater Pulse-1A in the South Atlantic Ocean deep circulation since the Last Glacial Maximum

Since 21 000 yr ago, the oceans have received large amounts of freshwater in pulses coming from the melting ice sheets. A specific event, known as meltwater pulse 1A (MWP-1A), has been identified in sea-level and temperature proxy records as responsible for the increase of ~20 m in sea level in less than 500 yr. Although its origin and timing are still under discussion, MWP-1A seems to have had a significant impact on several components of the climatic system. The present work aims to elucidate these impacts on the water mass distribution of the South Atlantic Ocean through the analysis of a transient simulation of the climate evolution from the Last Glacial Maximum to Present Day using a state-of-art CGCM, the National Center for Atmospheric Research Community Climate System Model version 3 (NCAR CCSM3). Results show that the freshwater discharge associated with the timing of MWP-1A was crucial to establish the present thermohaline structure associated with the North Atlantic Deep Water, marking the transition between a shallower and a deeper Atlantic Meridional Overturning Circulation.CAPES - Ciências do MarCNPq / PROANTARINCT Criosfer

Mean and Variability of the Tropical Atlantic Ocean in the CCSM4

This study analyzes important aspects of the tropical Atlantic Ocean from simulations of the fourth version of the Community Climate System Model (CCSM4): the mean sea surface temperature (SST) and wind stress, the Atlantic warm pools, the principal modes of SST variability, and the heat budget in the Benguela region. The main goal was to assess the similarities and differences between the CCSM4 simulations and observations. The results indicate that the tropical Atlantic overall is realistic in CCSM4. However, there are still significant biases in the CCSM4 Atlantic SSTs, with a colder tropical North Atlantic and a hotter tropical South Atlantic, that are related to biases in the wind stress. These are also reflected in the Atlantic warm pools in April and September, with its volume greater than in observations in April and smaller than in observations in September. The variability of SSTs in the tropical Atlantic is well represented in CCSM4. However, in the equatorial and tropical South Atlantic regions, CCSM4 has two distinct modes of variability, in contrast to observed behavior. A model heat budget analysis of the Benguela region indicates that the variability of the upper-ocean temperature is dominated by vertical advection, followed by meridional advection.National Science FoundationNational Science FoundationDepartment of EnergyDepartment of EnergyNCARNCARLANLLANLU.S. Department of Energy (DOE)U.S. Department of Energy (DOE)DOE Office of ScienceDOE Office of ScienceNSF-OCE [0928473]NSFOCECNPqMCT/INCTCNPq-MCT/INCTFAPESPFAPESPNOAAs Climate Variability and Predictability (CVP) programNOAA's Climate Variability and Predictability (CVP) progra

Quantifying Antarctic deep waters in SODA reanalysis product

The Antarctic intermediate and deep water masses present in the Atlantic sector of the Southern Ocean were quantified through the inverse method known as Optimum Multiparameter (OMP) analysis. The method was applied to the Simple Ocean Data Assimilation (SODA) product, which assimilates real observed ocean data into a hydrodynamic model. Results here show that the SODA dataset is able to capture reasonably well the intermediate and deep water mass (i.e. Warm Deep Water, Weddell Sea Deep Water, Weddell Sea Bottom Water, and Circumpolar Deep Water) regional distribution and contribution to the total mixture in the Weddell Sea and Weddell-Scotia Confluence. Those regions are, respectively, the main Antarctic Bottom Water source and export areas to the global ocean. We infer some aspects of the ocean circulation from the water mass distribution obtained. However, some efforts are still needed to better represent the deep salinity in these areas. The weak representation of this hydrographic parameter could be associated with the model’s lack of important cryospheric processes directly involved with bottom water formation

The annual cycle of the Atmosphere heat budget fousing on the southern hemisphere

Based on NCEP/NCAR reanalysis and World Ocean Atlas 2005, the long-term variation of the Atmosphere heat budget has been investigated. The aim of this work was to evaluate the role of each component of the climate system on the planet energy balance, focusing on the atmospheric variability over the Southern Ocean and the Antarctic Continent. The calculation was performed according to the formulation used by Oort and Vonder Haar (1976). As expected, the ocean has shown a huge dominance on heat storage around the globe. A large seasonal variation on both oceanic and atmospheric systems was evident. Results show unusual atmospheric variability over the southern polar region. After removing the seasonal cycle, the atmospheric heat storage anomaly displays significant intraseasonal variability at high latitudes. EOF and Wavelets analysis show that the atmospheric heat storage changed from the beginning of the record with a distinct 2 months cycle, which is well defined between 60◦S and 90◦S. According to the EOF analysis it grew more intense from mid 20th to early 21st centuries, reflecting the warming trend.Utilizando dados da re-análise NCEP/NCAR e do World Ocean Atlas 2005, foi investigada a variação de longo termo do balaço de calor da atmosfera. O objetivo deste trabalho foi avaliar o papel de cada componente do sistema climático no balanço de energia do planeta, especialmente a variabilidade atmosférica sobre o Hemisfério Sul e o continente antártico. Foi adotada a formulação proposta por Oort and Vonder Haar (1976). Como esperado, o oceano apresentou grande dominância em termos do armazenamento do calor no âmbito global. A variabilidade sazonal ficou evidente tanto para o oceano quanto para atmosfera. Foi observada uma variabilidade incomum no termo atmosférico sobre a região polar sul. Removendo o ciclo sazonal, a anomalia do armazenamento de calor pela atmosfera mostra uma variabilidade em escala intrasazonal em altas latitudes. Análises de EOF e Wavelets mostram que o armazenamento de calor pela atmosfera alterou-se entre o início e o fim do período analisado, evidenciando uma oscilação com período de 2 meses muito bem marcada entre as latitudes de 60◦S e 90◦S. De acordo com a EOF, esse modo de variabilidade intensificou-se entre meados do século XX e início do século XXI, refletindo a tendência de aquecimento

The Southern Ocean and Its Climate in CCSM4

The new Community Climate System Model, version 4 (CCSM4), provides a powerful tool to understand and predict the earth's climate system. Several aspects of the Southern Ocean in the CCSM4 are explored, including the surface climatology and interannual variability, simulation of key climate water masses (Antarctic Bottom Water, Subantarctic Mode Water, and Antarctic Intermediate Water), the transport and structure of the Antarctic Circumpolar Current, and interbasin exchange via the Agulhas and Tasman leakages and at the Brazil-Malvinas Confluence. It is found that the CCSM4 has varying degrees of accuracy in the simulation of the climate of the Southern Ocean when compared with observations. This study has identified aspects of the model that warrant further analysis that will result in a more comprehensive understanding of ocean-atmosphere-ice dynamics and interactions that control the earth's climate and its variability.National Science Foundation (NSF) [0908675]National Science Foundation (NSF)Office of Science of the U.S. Department of Energy (DOE-OoS)Office of Science of the U.S. Department of Energy (DOEOoS)NSFOCENSF-OCE [0928473]Department of Climate Change and Energy EfficiencyDepartment of Climate Change and Energy EfficiencyCSIRO (BMS)CSIRO (BMS)CNPqMCT/INCTCNPq-MCT/INCTFAPESPFAPES

Globalization of the Antarctic seas: Pollution and Climate Change Perspectives

The Antarctic continent is entirely surrounded by the Antarctic Ocean alsonamed Southern Ocean, forming a barrier to the movement of organismsinto and out of Antarctica. Therefore, the Antarctic Continent has uniquecharacteristics because of its geographic isolation.It is regarded as one of the remaining environments on the planetwhere human activities have little direct impact. Thus, this region hasbeen considered an ideal observatory for research on global change andenvironmental impacts caused by man (Xuebin et al. 2006).Fil: Montone, Rosalinda. Instituto Oceanografico (iousp); Brasil. Universidade de Sao Paulo; BrasilFil: de Castro Martins, Cesar. Centro de Estudos do Mar, UFPR; BrasilFil: Maruch Tonelli, Marcos Henrique. Universidade de Sao Paulo; Brasil. Instituto Oceanografico (iousp); BrasilFil: Hoppe Trevizani, Tailisi. Universidade de Sao Paulo; Brasil. Instituto Oceanografico (iousp); BrasilFil: Caruso Bicego, Marcia. Universidade de Sao Paulo; Brasil. Instituto Oceanografico (iousp); BrasilFil: Lopes Figueira, Rubens Cesar. Universidade de Sao Paulo; Brasil. Instituto Oceanografico (iousp); BrasilFil: Coaracy Wainer, Ilana Elazari Klein. Universidade de Sao Paulo; Brasil. Instituto Oceanografico (iousp); BrasilFil: Marcovecchio, Jorge Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentin