Sea & Coastal Research

Zee & Kust Onderzoek    

ZKO - Data & Information Portal

Project: INATEX - Indian-Atlantic exchange in present and past climate

Project details

  
Acronym : INATEX
Full project name : Indian-Atlantic exchange in present and past climate
Initiating organisation : Utrecht University, Faculty of Science, Physics and Astronomy, Institute for Marine and Atmospheric research Utrecht
Project leader : W. P. M. de Ruijter
Supporting organisation(s)-
Financing :
Project number : 83908430
Start date : Jan 01, 2009
End date : Dec 31, 2014
    

Relations

Programme :ZKO - Oceans - National Programme Sea and Coastal Research - Oceans
Main project :-
    

Description

Description :

North-Atlantic and Indian Ocean climate variability appears to be tightly related. The observed increase of the amplitude of the North-Atlantic Oscillation (stronger westerlies) over the past decades is directly related to increased atmospheric convection in response to a warming Indian Ocean. Warm Indian Ocean waters flow into the South Atlantic and further northward as part of the global overturning circulation. Paleoceanographic records indicate that this inter-ocean connection around South Africa fluctuated considerably and abruptly in during (inter)glacial change, as southward transport was the only oceanic pathway for the Indian Ocean to dispose of its excess heat. On millennial time-scales that could explain why warming over the North Atlantic coincided with cooling of the Antarctic sector and vice versa. Observations and modeling suggest an important impact of the Indian-Atlantic inter-ocean connection on the strength and stability of the Atlantic overturning circulation, controlled by the (sub)tropical flows feeding it from upstream. These flows converge in the Mozambique Channel and the southern East Madagascar Current (EMC). North Atlantic and Antarctic cold water masses flow in opposite direction in the deep Indian Ocean. To understand their dynamics, an array of moored instruments will measure interannual variability across the Mozambique Channel and remain in operation for several years. A second array will be placed across the EMC. Combined with satellite data and high-resolution ocean-model simulations a complete picture should emerge of the varying flow in the western Indian Ocean presently feeding into the Indian-Atlantic Ocean connection. Further simulations will be executed under both present and glacial conditions, and assessed against new paleorecords of western Indian Ocean climate change over the past 60,000 years from sediment cores. Finally, simulations with the global climate model EC-EARTH will address the processes controlling the global atmospheric and oceanic (tele)connections between the Indian and Atlantic ocean-climate systems, particularly during abrupt North Atlantic climate change.

 

Progress: The INATEX program has taken off in the second half of 2009. All sub projects have been  manned (or womanned) in that period with a junior scientist: PhD students for the modelling sub projects (C1 and C2), postdocs for the observational components (A and B).

                        Observations and modeling suggest an important impact of the Indian-Atlantic inter-ocean connection on the strength and stability of the Atlantic overturning circulation. The connection is controlled by the strength and structure of the tropical and subtropical flows feeding it from upstream. These flows converge in the Mozambique Channel and the southern East Madagascar Current (EMC). North Atlantic and Antarctic cold water masses flow in opposite direction in the deep sea.

To obtain an accurate picture of these currents and their interannual variations measurements are taken across the Mozambique Channel with an array of moored instruments (INATEX A). It will remain in operation for several years and a second array will be placed across the EMC. Combined with satellite data and simulations using a high-resolution ocean-model (INATEX C) a complete picture should emerge of the varying flow in the western Indian Ocean feeding into the Indian-Atlantic Ocean connection. Simulations will be executed under both present and glacial climate conditions.

Comparisons will be made with paleo-reconstructions of western Indian Ocean climate over the past 60,000 years based on analyses of bottom sediments (INATEX B).

Finally, simulations with the global climate model EC-EARTH will enable investigation of the global atmospheric and oceanic (tele)connections between the Indian and Atlantic ocean and climate systems including its variations and possible abrupt North Atlantic climate changes related to changes over the Indian Ocean (INATEX C).

                        Collaborating groups are from royal NIOZ, KNMI, VUA and IMAU. ‘Actuo’ data collection (project A) is led by NIOZ with KNMI and IMAU. Modern sediment and paleo-data of project B are jointly retrieved by NIOZ and VUA.  The first joint INATEX A and B cruise took place 8-26 December in the Mozambique Channel with the SA research vessel Algoa. The moorings across the Channel were serviced and sediments from the sediment trap retrieved. The data are presently being analyzed. All data will be used for synthesis project C in which all groups participate. It has a global climate modelling component led by KNMI and an ocean modelling component led by IMAU.

Regular joint meetings form part of the program. A first meeting of the group of project leaders took place in October 2009. Here it was agreed to organize a regular bi-annual INATEX workshop to discuss progress and joint plans. The first workshop has taken place in February 2010 at KNMI.

First results were discussed amongst the different projects in plenary sessions. These are promising but it is too early in the program to have formal publications already.

 

Source: NWO