DFG Research Unit 1740: Atlantic Freshwater Cycle

The overarching theme of the research unit's work will be the analysis and understanding of the freshwater budget of the ocean, including the role, which surface freshwater fluxes (net evaporation minus precipitation plus run-off and sea ice melting) play in changing the salt content in the upper ocean.

Hereby, the research unit will focus on the Atlantic Ocean, one of the key climate relevant regions. Specifically, the questions will be addressed of how and how much the upper Atlantic Ocean contributes to the global hydrological cycle.

These questions are of fundamental and long-standing scientific concern. Moreover the subject 'water' is central to many questions dealt with under climate impact studies, including precipitation over land, the availability of water for drinking and irrigation, but also sea level rise. The research topic is therefore essential for many climate-related and socio-economic questions.

The research unit is guided by several key questions:

  • How variable is salinity in the Atlantic on sub-seasonal to decadal time scales and what role plays surface forcing (E-P-R) vs. ocean processes (e.g. lateral transports, diapycnal mixing) in modulating the salt content of the Atlantic, on basin scale and locally?
  • How does surface freshwater forcing influence ocean mixed layer dynamics in both the tropics and high latitudes of the Atlantic, how does it regulate heat exchange with the atmosphere, and how do these processes feedback on ocean-atmosphere coupling?
  • What is the role of the observed changes in surface freshwater forcing and sea ice for the regional and basin scale salinity budget and how can we improve our estimates of those processes?
  • How do varying surface fluxes of freshwater and heat generate temperature-salinity anomalies in mid-latitude central waters and how are such anomalies incorporated and transported in the low-latitude sub ducted water masses?
  • Which processes transfer freshwater from the surface to subsurface layers and drive the mixing at submesoscale?


Why now?

The opportunity to establish the Research Unit at this point in time is given by the fact that for the first time in history many new data sets are available now, that can be combined with numerical models (with and without data assimilation) and thereby enable us to finally approach the problem with sufficient observational backing - a situation that never existed before in history. 

Among those new observational capabilities are:

  1. the global Argo float system delivering about 3000 high-precision near-surface salinity measurements every 10 days,
  2. salinity measurements provided by the global surface-drifter network, moorings and other autonomous platforms,
  3. new or planned underway measurements obtained by research vessels (including German research vessels) providing high-precision surface salinity data along cross-ocean transects or during local process studies,
  4. new satellite-based measurements of surface salinity from the two new missions SMOS (ESA) and AQUARIUS (NASA), providing measurements of the surface salinity globally every 3 days with unprecedented coverage in space and time.

Jointly, the new observations will allow us for the first time in history:

  • to estimate the changing ocean salinity and transports of freshwater anomalies,
  • to document the resulting changes in the oceans circulation and transport properties as well in the CO2 uptake in the ocean,
  • to estimate ocean mixing processes and the surface freshwater fluxes (E-P, run-off, and sea ice) required to establish those changes,
  • to quantify freshwater budgets.



Salinity Science Seminar (FOR1740 and CCI+SSS User Meeting)

will take place in Hamburg from 26 to 27 September 2019.



EGU General Assembly 2019

will take place in Vienna, Austria between 7 April and 12 April 2019.


Ocean Salinity Science Conference 2018

From 5-9 November 2018,  FOR1740 Scientists participate the Ocean Salinity Science Conference in Paris and successfully presented their work there.


New For1740 puplication

New puplication by our PhD student Yao Fu about volume, heat, and freshwater transports within the Atlantic Meridional Overturning Circulation at 14.5° N


I, Scientist conference on gender, career path and networking

From 25-26 May 2018, our PhD-and PostDoc Students attended the I, Scientist meeting in Berlin with lots of inspiring talks and discussions. Here are a couple of informations and thoughts.



Ocean Salinity Science Conference 2018

will take place in Paris from  6 to 9 November. Deadline for abstract submission is 6 July.


New FOR1740 puplications

New puplications by our researcher Julian Liman about the uncertainty characterization of latent heat-flux-related parameters (HOAPS 3.3)


FOR1740 scientists @ OSM18

Presenting posters with scientific results from satellite-retrieved, in situ and model salinity data, the FOR1740 project participates in the Ocean Science Meeting 2018.


News from Climate Science

NDR-Interview with our scientist Christian Klepp about measuring oceanic precipitation using optical disdrometers


New FOR1740 puplication

New puplication by our postdoctoral researcher Julia Köhler


Ocean salinity session at the AGU Fall Meeting 2017

Next week, the  "Ocean salinity and its role in ocean dynamics and the water cycle" session will take place at the AGU Fall Meeting 2017 in New Orleans, Luisiana, USA.


News from Climate Science

Christian Klepp shares his latest findings in the Hamburger Abendblatt and Welt and explains how to measure oceanic precipitation with shipboard disdrometers.



Release of HOAPS 4.0

HOAPS 4.0 surface freshwater flux data has finally been officially released (period 1987-2014).



New FOR1740 puplications

New puplications by our postdoctoral researcher Jörg Burdanowitz and our PhD candidate Xin Liu.



FOR1740 young researcher at the GODAE OceanView International Summer School 

Last week, our PhD student Aurpita Saha (IfM Hamburg) participated at the 2-week international school for observing, assimilating and forecasting the ocean in Mallorca, Spain.



Workshop on Global Ocean Salinity and the Water Cycle

will take place at the Woods Hole Oceanographic Institution, USA between 22 May and 26 May 2017.


PhD defense

Our PhD candidate Jörg Burdanowitz successfully defended his thesis titled "Point-to-area validation of passive microwave satellite precipitation with shipboard disdrometers".


News from Climate Science

Our postdoctoral researcher Julia Köhler talks about the importance of salinity measurements to understand changes in the global hydrological cycle.