Posters - Sea Level Rise, Ocean/Ice Shelf Interactions and Ice Sheets

Improved Antarctic Surface Mass Balance Remote Sensing using ASCAT
A. D. Fraser¹, S. Wotherspoon², H. Enomoto³, N. W. Young^1,4.
1 Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Australia
2 Institute for Marine and Antarctic Studies, University of Tasmania, Australia
3 National Institute of Polar Research, Japan
4 Australian Antarctic Division, Australia

Elephant seals confirm the dense Shelf Water sources for Cape Darnley Bottom Water, offering cost-effective long-term monitoring of Prydz Bay and surrounds
G. Williams¹, F. Roquet², L. Herraiz-Borreguero¹, I. Field³, M. Hindell⁴, T. Tamura⁵
1 ACECRC
2 Department of Meteorology, Stockholm University
3 Macquarie University, Australia
4 Institute for Marine and Antarctic Studies, Australia
5 National Institute of Polar Research, Tachikawa, Japan

Past and future sea-level change from the surface mass balance of glaciers
B. Marzeion, A. H. Jarosch, and M. Hofer
Institute of Meteorology and Geophysics, University of Innsbruck, Austria

Tidal Effects on Ice Shelves in the Amundsen Sea
R. Robertson
Univ. of New South Wales Canberra, Australia

Impact of self-attraction and loading effects induced by shelf mass loading on projected regional sea level rise
K. Richter^1,2, R. E. M. Riva³, and H. Drange^1,2,4
1 Geophysical Institute, University of Bergen, Norway.
2 Bjerknes Center for Climate Research, Norway.
3 Dept. Geoscience and Remote Sensing, Delft University of Technology, Netherlands
4 Uni Research AS, Norway

Recent status of development of a numerical ice sheet/shelf/stream model ICIES
F. Saito¹, A. Abe-Ouchi¹, K. Takahashi¹ and T. Obase²
1 Japan Agency for Marine-Earth Science and Technology
2 Atmosphere Ocean Research Institute, University of Tokyo

Melting of the Greenland ice sheet and its climate impact over the next centuries in an Earth system model
W. Wei, G. Lohmann, D. Barbi, K. Grosfeld and M. Thoma
Alfred Wegener Institute for Polar and Marine Research, Germany

Simulations of ocean-ice shelf interactions in the Parallel Ocean Program (POP)
X. Asay-Davis^1,2, M. Maltrud³
1 New York University, USA
2 Potsdam Institute for Climate Impact Research, Germany
3 Los Alamos National Laboratory, USA

Comparison of Steric Sea Level from an Ensemble of Ocean Reanalyses and Objective Analyses
Andrea Storto* and the CLIVAR/GSOP intercomparison Group
*Centro Euro-Mediterraneo per I Cambiamenti Climatici (CMCC), Italy

Southern Ocean climate in a suite of forced global ocean-ice simulations
R. Farneti and the CORE-II participants
Earth System Physics Section, International Centre for Theoretical Physics, Italy

Sea Level Variability in the Community Earth System Model
S. C. Bates and Y.-H. Tseng
NCAR, USA

CESM simulation study about the AMO impacting on Antarctic Climate and Sea-Ice during Austral Summer
X. Li
New York University, USA

Snowfall-driven mass change on the East Antarctic Ice Sheet
Carmen Boening, Matt Lebsock, Felix Landerer, and Graeme Stephens
Jet Propulsion Laboratory, California Institute of Technology, USA

Sea level rise during surface warming hiatus periods
N. Maher^1,2, M. England^1,2 and A. Sen Gupta^1,2
1 Climate Change Research Centre, University of New South Wales, Australia
2 Australian Research, Council Centre of Excellence for Climate System Science, Australia

Projection of subtropical gyre circulation changes and associated sea level changes in the Pacific
X. Zhang, J. A. Church, S. Platten and D. Monselesan
Centre for Australian Weather and Climate Research, CSIRO Marine and Atmospheric Research, Australia

Ocean and Land-Ice Interaction: Consequences of Sea-Level Rise in Bay of Bengal in Indian Ocean
Sahana Bose
Jawaharlal Nehru University, India

Shore line changes and Sea Level Rise along East coast of India: Implications to Climate Change
N. Jayaraju
Dept of Geology, Y.V.University, India

Subsidence in the coastal zone of Bangladesh
N. Mamnun
Nansen-Bangladesh International Centre for Coastal, Ocean and Climate Studies (NABIC), Bangladesh

Mass-induced and steric sea-level changes from ice-sheet melting
K. Lorbacher, S.J. Marsland, J.A. Church, S.M. Griffies and D. Stammer

Toward a new generation climate model: resolving multiscale processes in the ocean
Q. Wang, D. Sidorenko, T. Rackow, T. Semmler, R. Timmerman, X Wang, S. Danilov, J. Schröter, T. Jung
Alfred Wegener Institute for Polar and Marine Research, Germany

Mesoscale eddy contributions to the meridional transports of freshwater in the ocean
A.M. Treguier¹, J Deshayes¹, C. Lique², J.M. Molines³
1 Laboratoire de Physique des Océans, CNRS-Ifremer-IRD-UBO, France
2 Joint Institute for the Study of Atmosphere and Ocean, University of Washington, USA
3 LEGI, France

Physical constraints on the energetics of bottom and deep water sinking and on rates of conversion between potential and kinetic energy in the ocean
J. A. Saenz, A. Hogg, R. Griffiths, P. Spence

Modelling Antarctic Bottom Water (AABW) Overflow in Global Climate Models
Kate Snow¹, Dr Andy Hogg¹, Dr Stephanie Downes¹, Dr Bernadette Sloyan², Dr Marshall Ward¹
1 Research School of Earth Sciences and ARC Centre of Excellence for Climate System Science, The Australian National University, Australia
2 Centre for Australian Weather and Climate Research, CSIRO, Australia

Improved Antarctic Surface Mass Balance Remote Sensing using ASCAT
A. D. Fraser¹, S. Wotherspoon², H. Enomoto³, N. W. Young^1,4
1 Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Australia
2 Institute for Marine and Antarctic Studies, University of Tasmania, Australia
3 National Institute of Polar Research, Japan
4 Australian Antarctic Division, Australia

Large scale distribution of Antarctic Surface Mass Balance (SMB) is currently poorly understood. High quality in situ measurements of SMB are sparse, particularly in the interior of the continent. Remotely-sensed parameters can be used to guide interpolation between in situ measurement. Traditionally, the passive microwave (C-band) polarisation ratio, which is sensitive to layers of different dielectric properties in the upper snowpack (a proxy for SMB), has been used to guide interpolation of SMB points. We present evidence that alternative parameters may be more suitable maps upon which to base interpolated fields. These maps come from the EUMETSAT ASCAT C-band scatterometer, which was launched in 2007. These maps are sensitive to recently-mapped extensive areas of surface wind glaze which are areas of near-zero net accumulation, and thus are less prone to overestimation of SMB compared with earlier large-scale SMB maps. A primary output of this work will be a new SMB map of the Antarctic continent based on these improved fields.

Antarctic Bottom Water (AABW) production, from the downslope mixing of Dense Shelf Water (DSW), supplies the abyssal layer of the world ocean and is vital to the global climate system. A local variety of AABW has long been indentified in the eastern sector of the Weddell-Enderby Basin, but its precise DSW source and downslope mixing pathways have been elusive until now. Recently, the first observations of newly formed AABW cascading down the continental slope near 68ºE have refocused attention on the enhanced sea ice production in the polynyas of Cape Darnley and Prydz Bay. Here we document the DSW sources for this ‘Cape Darnley’ Bottom Water (CDBW), using unique data from instrumented southern Elephant seals (Mirounga leonina). We present the first observations of i) very high salinity DSW (>34.8) on the Cape Darnley shelf region and ii) the subsequent overflows of modified Shelf Water on the upper continental slope north of Cape Darnley. This study cements the resurgent story of CDBW and represents an important shift in our understanding of total and regional AABW production.

Past and future sea-level change from the surface mass balance of glaciers
B. Marzeion, A. H. Jarosch, and M. Hofer
Institute of Meteorology and Geophysics, University of Innsbruck, Austria

We present a model of the global surface mass balance of glaciers, based on the reconstruction and projection of the surface mass balance of all the world's individual glaciers, excluding the ice sheets in Greenland and Antarctica. The model is validated using a leave-one-glacier-out cross validation scheme using 3997 observed surface mass balances of 255 glaciers, and against 756 geodetically observed, temporally integrated volume and surface area changes of 341 glaciers. When forced with observed monthly precipitation and temperature data, the world's glaciers are reconstructed to have lost mass corresponding to 114+/-5 mm sea level equivalent (SLE) between 1902 and 2009. Using projected temperature and precipitation anomalies from 15 coupled general circulation models from the Coupled Model Intercomparison Project phase 5 (CMIP5) ensemble, they are projected to lose additionally either 148+/-35mm SLE (scenario RCP26), 166+/-42mm SLE (scenario RCP45), 175+/-40(mm SLE (scenario RCP60), or 217+/-47mm SLE (scenario RCP85) during the 21st century. Based on the extended RCP scenarios, glaciers are projected to approach a new equilibrium towards the end of the 23rd century, after having lost either 248+/-66mm SLE (scenario RCP26), 313+/-50mm SLE (scenario RCP45), or 424+/-46mm SLE (scenario RCP85). Up until approximately 2100, ensemble uncertainty within each scenario is the biggest source of uncertainty for the future glacier mass loss; after that, the difference between the scenarios takes over as the biggest source of uncertainty. Ice mass loss rates are projected to peak 2040-2050 (RCP26), 2050-2060 (RCP45), 2070-2090 (RCP60), or 2070-2100 (RCP85).

Tidal Effects on Ice Shelves in the Amundsen Sea
R. Robertson
Univ. of New South Wales Canberra, Australia

Tidal effects on circulation under the ice shelves and melting of the ice shelves in the Amundsen Sea were investigated using a numerical tidal model, comparing simulations with and without tides. Tidal effects were found to depend on the location of the ice shelf with respect to the M2 effective critical latitude, which is where the tidal frequency equals the inertial frequency adjusted by relative vorticity, such as that associated with a wind-driven gyre. For ice shelves located equatorward of the effective critical latitude, tides increased both mixing in front of and under the ice shelf and flow into the ice shelf cavities by as much as a 50%, despite weak tides compared to the mean flows. Tides also increased melting for these ice shelves by 2-3 m yr-1. For ice shelves located poleward of the critical latitude, tides retarded flow into the cavity and slightly reduced melting.

Presently, global sea level rise at a rate of 3 mm/yr and is expected to continue to rise in the future. The rise is not spatially uniform but varies geographically. This is mainly due to non-uniform steric changes and the uneven distribution of meltwater from land ice. The investiagtion of these steric changes and its implications is the purpose of this study. We use 20 models participating in CMIP5 (RCP8.5) to compute global average steric height changes and regional sea surface height (SSH) changes. In addition, the Norwegian Earth System Model (NorESM1-M) is used to investigate regional steric height changes and SSH changes due to redistribution of sea water, and to quantify the magnitude of self attraction and loading (SAL) effects for three RCP-scenarios. We find that, depending on the scenario and region, SAL effects may result in an additional sea level rise of 1-3 cm on the world's continental shelf areas by the end of the 21st century. These estimates are at most 15 % of the combined changes in sea surface height induced by redistribution of water masses and steric expansion.

Ice sheet model for Integrated Earth-system Studies (ICIES) has been developed to simulate Greenland and Antarctic ice sheets as well as paleo-climate studies of past Northern Hemisphere ice sheets.

Now we have been restructuring and improving the model to implement

MPI parallelization for higher-resolution experiments
Shallow-shelf approximation and Shelfy-stream approximation for better understanding of past/future migration of grounding-line

In this study, we report the recent status of development of ICIES and demonstrate it under ideal as well as realistic conguration such as:

Sensitivity of response of Greenland ice sheet to global warming on surface mass balance parameterization and reference climate states, using shallow-approximation model
Sensitivity studies of grounding line migration under MISMIP-type conguration and Antarctic ice sheet

Rapid mass loss of the Greenland Ice Sheet (GrIS) has been observed in the last decades, which is attributed to the anthropogenic induced global warming. During the melting of the GrIS, the albedo effect and the elevation effect have strong positive feedback on the temperature change, both locally and globally. Its melting brings huge amount of freshwater into the North Atlantic, contributing to the global sea level rise and potentially changing the ocean circulation. Considering that the greenhouse gas will keep increasing as indicated by the IPCC emission scenarios, it is crucial to investigate the mass balance of the GrIS over the next centuries and its possible climate influence, e.g. sea level rise. In this study, we perform the IPCC AR5 scenarios using the Earth system model COSMOS with and without dynamic ice sheets. The results will allow us to predict the future GrIS mass balance and give both temporal and spatial evolution of the GrIS over the next centuries under different greenhouse gas concentrations. Comparison between different setups can be served as a constraint for the current IPCC models to estimate their biases of various climate parameters when there is no dynamic ice sheet included. Meanwhile, the potential impact of the GrIS melting on the global climate will be presented.

We present a series of simulations using POP2X, a modified version of the LANL Parallel Ocean Program version 2 (POP2) that includes circulations in ice-shelf cavities. The geometry of the ice-shelf/ocean interface is represented using the partial top cells, following the approach developed by Losch (2008). One of our test cases is an idealized domain reminiscent of the Ronne-Filchner Ice Shelf cavity. Vertical model resolution can have a strong impact on the melt rate and circulation in the vicinity of the ice shelf. We have also performed decadal-scale simulations using a 0.1 degree Southern Ocean regional configuration of POP with four ice shelves (Ronne-Filchner, Ross, Amery, Pine Island). Including these shelves results in modified circulation and water properties in the cavities compared to a control run without ice shelves.

During one of the last CLIVAR/GSOP and GODAE meetings, it was established a joint initiative among ocean synthesis producing centers in order to extensively compare some climate key parameters. CMCC is leading the intercomparison of the steric sea level (SSL), with the scientific objectives of i) quantify the global SSL, its uncertainty and the reanalyses skill with respect to independent estimates; ii) assess the regional SSL change and the agreement between the ocean reanalyses; iii) quantify the relative contributions of the thermal and haline components and iv) quantify the relative contributions of different vertical regions. We present here the first results from the intercomparison study, which involved 19 products, of which 15 ocean reanalyses and 4 observation-only products, thus representing a major effort in evaluating the SSL provided by the state-of-the-art ocean reanalyses.

The comparison strategy consists of a validation period (2005-2009) and an extended intercomparison period (1993-2009), the former covering the gravimetry era, while the latter the altimetry era. Within the validation period, the ocean synthesis products are compared with the independent SSL estimation given by monthly means of altimetric sea-level anomaly minus gravimetric ocean bottom mass anomaly, the latter from the ensemble of the GRACE RL05 solutions.

For the validation period, it turned out that the Global SSL (GSSL) fluctuations are quite well reproduced by the reanalyses, its ensemble mean leading to an anomaly correlation of 0.85 with the independent satellite estimates; the seasonality of the GSSL is generally well reproduced while linear trends exhibit large uncertainty and variability among the reanalyses and are generally under-estimated. Interestingly, the ensemble of the ocean reanalyses is more skillful than the ensemble of objective analyses (i.e. observation-only products), especially in areas with a poor observing network and/or impact of deep and bottom waters (e.g. ACC, Bering Sea). The ensemble mean itself proves a robust tool for further diagnostics.

For the extended intercomparison period, we generally found no consensus on the relative contributions of the thermal and haline components of the GSSL: while the halosteric contribution impact on the GSSL trend is generally neutral or slightly negative, there is no clear consensus on its contribution to the GSSL variability, its explained variance ranging from 2 to 75 % depending on the ocean. Finally, we have assessed the contribution of the “unobserved ocean” (considered below 700 m for the 1993-2009 period), which accounts for the 25% of the interannual signal variability in the case of the reanalyses ensemble. Further diagnostics focusing on the spatial patterns of the relative contributions are being assessed and will be presented as well.

Southern Ocean climate in a suite of forced global ocean-ice simulations
R. Farneti and the CORE-II participants
Earth System Physics Section, International Centre for Theoretical Physics, Italy

The Coordinated Ocean-Ice Reference Experiment (CORE) version II is an experimental protocol for ocean-ice coupled simulations forced with interannually varying atmospheric data sets for the period 1948-2007. This effort, involving several centers around the world, is coordinated by the CLIVARWorking Group on Ocean Model Development (WGOMD). The hindcast simulations provide a framework for both model evaluation and studying variability and change at seasonal to decadal time scales. Several regional studies are planned and currently underway.

We present an intercomparison that focuses on the recent evolution of the Southern Ocean as simulated by the different models. We focus on the mean state and variability of the Antarctic circumpolar current (ACC), the meridional overturning circulation (MOC), as well as water masses and their ventilation. To do this, we consider the evolution of the drivers of these circulations, both wind stress and buoyancy forcing, and of the interior structure of the Southern Ocean. Models of different resolutions are considered, from coarse to eddy-permitting/resolving, and an attempt is made to evaluate the role of mesoscale eddies and their parameterization. Comparison with observational estimates is made when possible. The identification of the strengths and weaknesses of ocean models with respect to the evolution of the Southern Ocean and its global consequences is also a key aim of the study.

Sea Level Variability in the Community Earth System Model
S. C. Bates and Y.-H. Tseng
NCAR, USA

The focus of this work is to examine the patterns of sea level variability in the Community Climate/Earth System Model (CCSM/CESM), which is tightly connected to the future ocean climate projection but to date has never been done. We will examine the modeled dominant modes of the sea level pattern variability in the north Atlantic and Pacific ocean basins and compare with satellite observations. The impacts of recent decadal warming and natural (internal) variability will be assessed using the 20th Century and 1850 control simulations. Consistent with observations, all five ensemble members of the 20th Century CCSM4 simulations exhibit accelerated surface warming in the late 20th Century. We will investigate the modeled sea level variability and trending in relation to this warming. A long control simulation with no transient forcing, called the 1850 control simulation, will also be investigated and compared to examine the modeled natural (internal) sea level variability.

CESM simulation study about the AMO impacting on Antarctic Climate and Sea-Ice during Austral Summer
X. Li
New York University, USA

In this work, the relationship between the Atlantic Multidecadal Oscillation (AMO) and Antarctic regional climate and the sea-ice distribution are discussed. A series statistic analysis (Regression, EOF and Maximized Covariance Analysis) were performed, using ECMWF, MERRA and Hadley Center SST/Sea Ice reanalysis data, which shows that the AMO is highly related to the distribution of the sea ice around West Antarctica, as well as the Polar Climate. We then perform a series of simulation using CESM, by
changing the heat flux from the Ocean to the atmosphere (as well as the sea ice distribution, the Greenhouse Gas and Ozone). The results shows that the SST change in Atlantic region can enhance the deep convection, which further impact on subtropical jet, generate a Rossby Wave and propagate to
Antarctic Region. The linearity of Model response to the SST forcing are also discussed by dramatically changing the amplitude of SST forcing.

An improved understanding of processes dominating the sensitive balance between mass loss primarily due to glacial discharge and mass gain through precipitation is essential for determining the future behavior of the Antarctic ice sheet and its contribution to sea level rise. While satellite observations of Antarctica indicate that West Antarctica experiences dramatic mass loss along the Antarctic Peninsula and Pine Island Glacier, East Antarctica has remained comparably stable. In this study, we describe the causes and magnitude of recent extreme precipitation events along the East Antarctic coast that led to significant regional mass accumulations that partially compensate for some of the recent global ice mass losses that contribute to global sea level rise. The gain of almost 350 Gt from 2009 to 2011 is equivalent to a decrease in global mean sea level at a rate of 0.32 mm/yr over this three-year period.

The anthropogenic increase in greenhouse gases in the atmosphere results in a radiative imbalance at the top of the atmosphere, which subsequently causes a non-linear increase in both land and sea surface temperatures. However, the observational record of surface air temperature reveals decadal periods with no significant change or in some cases a decrease in the global mean. These decades have been termed ‘hiatus’ periods. During these hiatus periods, there is still net increase in the input of radiation at the top of the atmosphere, and so the energy surplus must be modifying other components of the climate system. Here we examine what happens to this extra energy during hiatus periods.

We have undertaken an analysis of CMIP5 models, with a focus on the ACCESS model. Decadal long hiatus periods are identified within the models and assessed to test the hypothesis that the ‘missing’ energy is being used to heat the oceans below the sea surface. We investigate how and where deep ocean heat content anomalies penetrate the interior on decadal timescales. Where possible, comparisons with the observational record are made.

We use these results to compute sea level changes during hiatus periods. We examine the hypothesis that the extra energy is heating the oceans below the sea surface, so that although the sea surface is not significantly warming, sea level will rise due to warming in the sub surface ocean.

According to the intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), sea level is projected to rise globally under different emission scenarios. The sea level changes are not going to be geographically uniform, with many regions departing significantly from the global average. Some of regional distributions of sea level changes can be explained by projected changes of ocean density and dynamics. In this study, with 11 available Coupled Model Intercomparison Project Phase 3 (CMIP3) climate models, we identify an asymmetric feature of projected subtropical gyre circulation change and associated sea level change between the North and South Pacific, through analysing projected changes of related parameters, such as ocean dynamic height (with reference to 2000 db), depth integrated steric height, Sverdrup stream function, surface wind stress and its curl. Poleward expansion of subtropical gyres is projected in the upper ocean for both North and South Pacific. Contrastingly, the subtropical gyre circulation is projected to spin down for about 20% in the subsurface North Pacific from the main thermocline around 400 m to at least 2000 m, while the South Pacific subtropical gyre is projected to strengthen for about 25% and expand poleward in the subsurface to at least 2000 m. Such asymmetrical distribution of the projected subtropical gyre circulation changes is directly related to differences in projected changes of temperature and salinity between the North and South Pacific, forced by surface heat and freshwater fluxes, and surface wind stress changes.

Ocean and Land-Ice Interaction: Consequences of Sea-Level Rise in Bay of Bengal in Indian Ocean
Sahana Bose
Jawaharlal Nehru University, India

The world’s largest mangrove-dominated Sundarbans delta situated between India and Bangladesh at the mouth of Bay of Bengal, contributes to the maximum deposits of terrestrial sediments along with glacial melt water throughout the year in Indian Ocean. This giant delta is feed by the Ganges, Brahmaputra and Meghna Rivers which contributes about a billion tons (1012 kg) of sediments annually to the Bengal basin. Ganges and Brahmaputra originate in the still rising Himalayan orogenic belt and reach the sea across the tectonically active Bengal basin. Melting of Himalayan Glaciers due to global warming has created more rainfall and cloud burst in high altitudes leading to massive rock weathering along the upper course of the rivers. Here the chemical denudation rates are 2 to 3 times higher than the world’s average. Water and sediments discharge of the rivers is driven largely by the South West Monsoon with maximum discharge in the month of June to October. This addition of mass to the ocean from land-ice sources has brought drastic steric changes of the Indian Ocean in recent years.

Objectives: This paper finds out the recent thermosteric and halosteric changes in Bay of Bengal due to addition of land-ice in the form of glacial melt water and what will be its impact on the coastal communities and marine resources? How these changes are affecting the atmospheric circulations of that particular region, why there is increase in frequencies of storm surges and tropical cyclones. This study is restricted to the northern portion of Bay of Bengal of Indian Ocean. Its talks about the depletion of world’s largest mangrove forests due to sea level rise. Projected impacts of sea level rise and other conclusions are drawn from this study, which are useful for policy implications and for preparing new ocean-climate models.

Methodology: Satellite data, government documents and reports are consulted for analysis and interpretations.

Major Findings: This study is based on 10-15 years data (year 1995-2010) to show the recent sea level rise in Indian Ocean due to maximum addition of glacial melt water in Bay of Bengal. This sudden increase in sediments influx from the Himalayas crystalline rock complexes has increased ocean warming. It is also observed that within this particular period, both the temperate and ocean salinity has increased drastically. Till the year 2000, the annual sea level rise (SLR) was 0.12 inches but afterwards the figure is crossing above 0.20 inches every year. There is depletion of mangrove forest due to excessive saline waters at the tidal estuarine. This sea has become more vulnerable for the occurrence of storm surges and tropical cyclones. Rising sea-surface temperature (SST) is one of the main factors contributing to increase in the frequency of cyclones and storm surges along with other atmospheric factors. The SLR may aggravate monsoon flooding in Bangladesh and India and could have far reaching impacts on both future regional and global climate. The United Nations Intergovernmental Panel on climate change predicts further sea level rise will submerge 17 percent of Bangladesh by 2050. More research is needed to integrate remote-sensing data such as SST and salinity, and global atmosphere-hydrosphere-cryosphere models that assimilate a new climatic data types to study this particular region.

Shore line changes and Sea Level Rise along East coast of India: Implications to Climate Change
N. Jayaraju
Dept of Geology, Y.V.University, India

India has 7,516 km of coastline, of which the mainland accounts for 5,422 km, Lakshadweep Islands coast extends for 132 km and the Andaman and Nicobar Islands extends for 1,962 km. The shoreline is one of the rapidly changing linear features of the coastal zone which is dynamic in nature. The issue of shoreline changes due to sea level rise over the next century has increasingly become a major social, economic and environmental concern to a large number of countries along the coast, where it poses a serious problem to the environment and human settlements. Shoreline recession as a result of rising sea level has been recognized as a potential near future hazard by a number of countries and this is same for the states of India along the coast. Today the issue of shoreline changes due to sea level rise which caused by Globe warming has increasingly become a major issues in terms of its impact on the population along the coastal area. Changes in mean sea level as measured by coastal tide gauges are called relative sea level Changes. In IPCC (Intergovernmental Panel on Climate Change) Third Assessment Report (2001) shows that global average surface temperature is projected to increase by 1.4 to 5.8° C over the period 1990 to 2100. This projected warming will be greater than that experienced over the last 10,000 years. Moreover, the global mean sea level is projected to rise by 0.09 to 0.88 m over the same period, as a result of the thermal expansion of the oceans, and the melting of glaciers and polar ice sheets. The physical effects of sea level rise are categorized into five types, inundation of low lying areas, erosion of beaches and bluffs, salt intrusion into aquifers and surface waters, higher water tables and increased flooding and storm damage. Sea level has been rising 1.7–1.8 mm/year over the last century and the rate has increased to 3 mm/year in the last decade. Sea level rise is contributing to coastal erosion in many places of the world .The tide gauge records at five coastal locations in India; Mumbai, Kolkata, Cochin, Kandla and Sagar Islands have reported an increase in sea level. The change in sea level appears to be higher on eastern coast compared to western coast. The average sea level rise for India has been reported as 2.5 mm/year since 1950’s The most significant and direct impact of the sea level rise may be the shoreline retreat and the loss of the coastal wetland as a result of the inundation of the low land. The impact of global warming-induced sea level has great significance to India due to its extensive low-lying densely populated coastal zone. This paper attempts to find the time trend of the sea level rise and document the positive, significant and increasing trend for the majority of the monitoring stations along east coast of India.

Subsidence in the coastal zone of Bangladesh
N. Mamnun
Nansen-Bangladesh International Centre for Coastal, Ocean and Climate Studies (NABIC), Bangladesh

Subsidence is one of the causes of variation in the relative sea level in local level. As Bangladesh is one of the most vulnerable countries, it is important to know the contribution of subsidence in sea level rise of Bangladesh for better projection of sea level change over her coast. The poster aims to give an overview of the rate and causes of in the coastal area of Bangladesh. Subsidence in the area is complex with no clear spatiotemporal pattern. Around the coast subsidence is 2-4 mm/year.

Mass-induced and steric sea-level changes from ice-sheet melting
K. Lorbacher, S.J. Marsland, J.A. Church, S.M. Griffies and D. Stammer

Sea level rise associated with idealized Greenland and Antarctic ice sheet melting events is examined
using the Australian global coupled ocean sea-ice model ACCESS that has a free surface formulation
and thus can simulate fast barotropic motions. The perturbation experiments follow the
Coordinated Ocean-ice Reference Experiment (CORE) version III.

The global mean sea level rises by 9 mm yr-1 after a polar meltwater input of 0.1 Sv (1 Sv ≡ 106 m3s-1). A linear relation between sea level rise and global meltwater input is further supported by
experiments in which idealized melting occurs only in a region east or west of the Antarctic
Peninsula, and when melting rates are varied between 0.01 Sv and 1.0 Sv. The results indicate that in
ocean models that do not explicitly represent the barotropic signal (because they use the virtual salt
flux boundary conditions), the barotropic component of sea level rise can be added off-line to the
simulated steric sea level evolution that is also connected with melt events.

However, for climate adaption in low-lying coastal and island regions, it is critical that the barotropic
sea level signal associated with melting events is taken into consideration. It leads to a sea level rise
within 7-8 days of the initialization from melting ice-sheets for all regions of the global ocean. This
fast mass-induced adjustment contrasts sharply with the slower adjustment associated with the one-order of magnitude smaller steric sea level signal.

The Finite Element Sea-Ice Ocean Model (FESOM) allows to use variable mesh resolution with focus on particular regions. This is useful for resolving dynamically important regions and bathymetry controlled flows in an otherwise coarse large scale model. Examples of FESOM applications will be given in the poster for Antarctic ice cavity simulations, water hosing experiments for Greenland Ice Sheet melting, and studies on the Weddell Sea Bottom Water formation from the Ice Shelf Water in the southern Weddell Sea. FESOM has been coupled to the atmospheric model ECHAM. The coupled model has been evaluated with relatively coarse resolution, varying from 150 to 20km in the ocean and T63L47 resolution in the atmosphere. We show that the climate state simulated by FESOM/ECHAM is in most cases within the spread of other climate models. A first water hosing experiment using the coupled model indicates that uncertainties in coupled model simulations can be large and it is challenging to predict the impact of increased ice sheet melting on ocean dynamics and dynamical sea level, as shown in other studies. The new model will serve as a tool for examining the model uncertainty by taking model resolution as one of the key parameters, while its complexity could also make this task challenging.

In the ocean, the budgets of water and salt are linked. They can be expressed through the freshwater balance. Mesoscale eddies are ubiquitous in the ocean, and contribute to the freshwater transport through lagrangian advection of water masses as well as through correlated fluctuations of velocity and salinity. Recent global and regional models at 1/12° resolution demonstrate the importance of these eddy fluxes. In the North Atlantic, the large eddy flux divergence out of the subtropical gyres (0.2 Sv) is not compatible with the observed salinity variations at the decadal scale, which implies that this eddy flux divergence must be compensated to a large degree by the convergence of the transport by the time-mean flow. Implications for the estimation of freshwater or salt balances from numerical models at the basin scale are discussed.

Physical constraints on the energetics of bottom and deep water sinking and on rates of conversion between potential and kinetic energy in the ocean
J. A. Saenz, A. Hogg, R. Griffiths, P. Spence

The current understanding of ocean energetics, based on the evaluation of several coarse resolution general circulation models (GCMs) in which convection and mesoscale eddies are parameterized, is that the global circulation involves a net (volume integrated) conversion from kinetic to available potential energy. Using physical arguments we show that, in a stably stratified ocean, the large scale circulation must result in the opposite: a net conversion from available potential energy to kinetic energy. A net transfer of kinetic to potential energy would require that the oceans be unstably stratified. We use this result to constrain the rates of conversion from potential to kinetic energy associated to sinking of deep and bottom waters that form at high latitudes. We discuss the effects that parameterizations have on the energetics of GCM solutions for the circulation and show new analyses from high resolution models that serve to clarify the pathways of energy transfer in the ocean.

Antarctic Bottom Water (AABW), the dominant abyssal water of the global ocean and an important distributor of energy, carbon and nutrients, provides a significant contributor to the global ocean energy and sea level budget. To more fully understand the AABW’s contribution to the global budgets, suitable representation of AABW formation and transport is required in global climate models (GCMs), processes currently poorly realized through the overflow parameterizations implemented in GCMs. Motivated by this poor representation, a sensitivity analysis of three different overflow parameterizations (a downslope transport scheme, a sigma bottom boundary layer scheme and an imbedded Lagrangian point particle method) is conducted using the Modular Ocean Model (MOM). Coupling MOM to the GFDL Sea Ice Simulator (SIS), the parameterizations are applied to a realistic-topography sector model of the Atlantic Ocean. Analyzing the sensitivity and performance of each parameterization provides an indication of the most suitable model for use in representing overflows in the Southern Ocean. Further, understanding of each parameterization’s performance is important for an accurate representation of the AABW and the deep ocean in GCMs, hence allowing a more reliable indication of bottom waters contribution to the global energy and sea level budgets.

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