Geographisches Institut


AQUATIC - Assessing and QUantifying the ATlantic Instrumental hydroClimate

Global warming is projected to have pronounced impacts on the hydroclimate — including rainfall and river flow — in the tropical Atlantic basin, which contains the world’s largest river systems and rainforests, and growing populations. The aim of AQUATIC is to compile recently-recovered measurements of precipitation, river discharge, and surface salinity from different archival sources to develop an integrated record of tropical Atlantic regional hydroclimate back to the late 19th century. These historical data will contribute to an understanding of the mechanisms of hydroclimate variability and constrain future climate projections.


A. R. Friedman, M. Bollasina, G. Gastineau, and M. Khodri. “Increased Amazon basin wet-season precipitation and river discharge since the early 1990s driven by tropical Pacific variability.” In press, Environmental Research Letters.

Schurer, A. P., G. C. Hegerl, A. P. Ballinger, and A.R. Friedman. “Human influence strengthens the contrast between tropical wet and dry regions.” Environmental Research Letters, 15, 104026.

A. R. Friedman, G. C. Hegerl, A. P. Schurer, S.-Y. Lee, W. Kong, W. Cheng, and J. C. H. Chiang. “Forced and unforced decadal behavior of the interhemispheric SST contrast during the instrumental period (1881–2012): contextualizing the late 1960s–early 1970s shift.” Journal of Climate, 33, 3487–3509.

G. C. Hegerl, S. Brönnimann, T. Cowan, A.R. Friedman, E. Hawkins, C. Iles, W. Müller, A. Schurer, and S. Undorf. “Causes of climate change over the historical record.” Environmental Research Letters, 14, 123006.

G. Gastineau, A. R. Friedman, M. Khodri, and J. Vialard. “Global ocean heat content redistribution during the 1998–2012 Interdecadal Pacific Oscillation negative phase.” Climate Dynamics, 53, 1187–1208.

G. Reverdin, A. R. Friedman, L. Chafik, N. P. Holliday, T. Szekely, H. Valdimarsson, I. Yashayaev. “North Atlantic extratropical and subpolar gyre variability during the last 120 years: a gridded dataset of surface temperature, salinity, and density. Part 1: dataset validation and RMS variability.” Ocean Dynamics, 69, 385–403.

G. Reverdin, H. Valdimarsson, G. Alory, D. Diverres, F. Bringas, G. Goni, L. Heilmann, L. Chafik, T. Szekely, and A. R. Friedman. “North Atlantic subpolar gyre along predetermined ship tracks since 1993: a monthly data set of surface temperature, salinity, and density.” Earth System Science Data, 10, 1403–15.

A. R. Friedman, G. Reverdin, M. Khodri, and G. Gastineau. "A new record of Atlantic sea surface salinity from 1896 to 2013 reveals the signatures of climate variability and long-term trends." Geophysical Research Letters, 44, 1866–1876. Featured in Geophysical Research Letters “Editors’ Highlights” (March 2017).

P. Rogé, A. R. Friedman, M. Astier, and M. A. Altieri. “Farmer strategies for dealing with climatic variability: A case study from the Mixteca Alta Region of Oaxaca, Mexico.” Agroecology and Sustainable Food Systems, 38 (7), 786-811.

A. R. Friedman, Y.-T. Hwang, J. C. H. Chiang, and D. M. W. Frierson. "Interhemispheric temperature asymmetry over the 20th century and in future projections." Journal of Climate, 26 (15), 5419-5433. Featured in Nature Geoscience “Research Highlights” (volume 6, p158: February 2013).

J. C. H. Chiang and A. R. Friedman. "Extratropical cooling, interhemispheric thermal gradients, and tropical climate change." Annual Review of Earth and Planetary Sciences, 40, 383-412. Web of Science highly cited paper: top 1% in Geosciences (September/October 2020).

C.-Y. Chang, J. C. H. Chiang, M. F. Wehner, A. R. Friedman, and R. Ruedy. “Sulfate aerosol control of Tropical Atlantic climate over the 20th century.” Journal of Climate, 24, 2540-2555.


G. Reverdin and A. R. Friedman. “Bin-averaged SSS in the Atlantic Ocean.” French Sea Surface Salinity Observation Service. doi: 10.6096/SSS-BINS-ATL.

G. Reverdin and A. R. Friedman. “Annually binned Sea Surface Salinity, Temperature and Density in the North Atlantic subpolar gyre (40°N-70°N).” French Sea Surface Salinity  Observation Service. doi: 10.6096/tsd-bins-naspg.