AMOC slowdown – Desdemona Despair

Diagrams showing parameters for the collapse of the Atlantic Meridional Overturning Circulation (AMOC). (A) The AMOC strength at 1000 m and 26°N, where the yellow shading indicates observed ranges (60, 61). The cyan-colored lines indicate the magnitude of FH. The red arrow indicates the AMOC tipping point (model year 1758; fig. S1, A and B), and the blue sections indicate the 50-year periods used in (B) to (D). Inset: The hosing experiment where fresh water is added to the ocean surface between 20°N and 50°N in the Atlantic Ocean (+FH) and is compensated over the remaining ocean surface (−FH). The black sections indicate the 26°N and 34°S latitudes over which the AMOC strength and freshwater transport (FovS) are determined, respectively. (B to D) AMOC streamfunction (Ψ) and Atlantic meridional heat transport (MHT; see also fig. S2) for model years 1 to 50, 1701 to 1750, and 2151 to 2200. The contours indicate the isolines of Ψ for different values. Graphic: Van Westen, et al., 2024 / Science Advances

May 27, 2024

Marker for the collapse of key Atlantic current discovered – “We are approaching the tipping point”

By Stephanie Pappas 9 February 2024 (Live Science) – Scientists have discovered a key warning sign before a crucial Atlantic current collapses and plunges the Northern Hemisphere into climate chaos. The Atlantic Meridional Overturning Circulation (AMOC) carries warm water north from the Southern Hemisphere, where it releases heat and freezes. The freezing process concentrates salt […]

A scientist with PROMIS/GEUS checks instruments on the Greenland ice sheet, 1 September 2021. The ice is darkened by an unprecedented algae bloom caused by persistent cloudy and rainy conditions in 2021 that promoted ice algae growth. Photo: GEUS

January 8, 2022

Algae blooms darken Greenland ice sheet after unprecedented rainfall in 2021 – “I never saw the ice as dark as this”

5 January 2022 (PROMICE) – GEUS and PROMICE professor Jason Box recently made the front page in Danish national media with testimony of algal blooms and rain on the Greenland ice sheet. PROMICE field work helps quantify the ice algae blooms and their effect on melting. In Autumn 2021, Professor Jason Box and two PROMICE […]

Map showing trends of early-warning indicators of Atlantic Meridional Overturning Circulation (AMOC) collapse. a, Linear trends of the corrected restoring rate λ estimated from the HadISST dataset assuming autocorrelated noise. b, Same as (a) but for the EN4 salinity dataset. c, Linear trends of the variance estimated from the HadISST dataset. d, Same as (c) but for the EN4 salinity dataset. e, Linear trends of the AC1 estimated from the HadISST dataset. f, Same as (e) but for the EN4 salinity dataset. Note the high positive values in the northern Atlantic and the subpolar gyre region in particular for λ and AC1, but also in the southern Atlantic ocean where a salinity pileup has recently been associated with an AMOC slowdown. Graphic: Boers, 2021 / Nature Climate Change

August 22, 2021

Gulf Stream could be veering toward irreversible decline, a new analysis warns – Atlantic current “approaching a critical threshold beyond which the circulation system could collapse”

By Ben Turner 6 August 2021 (LiveScience) – One of the most crucial ocean current systems for regulating the Northern Hemisphere’s climate could be on the verge of total collapse due to climate change, a new study has revealed. The Atlantic Meridional Overturning Circulation (AMOC), which includes the Gulf Stream and is responsible for moderating […]

Millennium-scale evolution of the Atlantic Meridional Overturning Circulation (AMOC), 400 - 2020. SST-based AMOC reconstructions (light and dark blue) compared to various proxy reconstructions, including land and sea surface temperature reconstructions, sortable silt data, δ18O in benthic foraminifera, δ15N of deep-sea gorgonian corals, and relative abundance of Turborotalita quinqueloba. Since at least 400 AD relatively stable, the AMOC began to decline during the 19th Century which is evident in all proxy records. Around 1950 a phase of particularly rapid decline started that is found in several, largely independent proxies. A short-lived recovery is evident in the 1990s before a return to decline from the mid-2000s. Together these data consistently show that the modern AMOC slowdown is unprecedented in over a thousand years. Graphic: Levke Caesar

March 21, 2021

Gulf Stream System at its weakest in more than a millennium – “This could bring us dangerously close to the tipping point at which the flow becomes unstable”

25 February 2021 (PIK) – Never before in over 1000 years the Atlantic Meridional Overturning Circulation (AMOC), also known as Gulf Stream System, has been as weak as in the last decades. This is the result of a new study by scientists from Ireland, Britain, and Germany. The researchers compiled so-called proxy data – taken […]

Observational and modeled climatology (contours) and trends (shading) of the zonal component of the near ocean surface wind. (a) Ensemble trends of the zonal near ocean surface wind based on the NCEP/NCAR, NCEP/DOE and NERA‐Interim reanalysis data sets covering 1979–2018. Stippling indicates regions where the trends pass the 95 percent confidence level (Student's t test). (b) Zonal near ocean surface wind change in the doubled CO2 simulations relative to the pre‐industrial control simulation carried out by AWI‐CM. Stippling indicates areas where the magnitude of the trend is larger than the standard deviation of the local variability. The subpanel at the right side of each graph shows the zonally averaged climatology (blue) and trend (red) of zonal near ocean surface wind. Graphic: Yang, et al., 2020 / Geophysical Research Letters

March 6, 2020

Major wind-driven ocean currents are shifting toward the poles – “Over the past 40 years, all eight wind-driven surface current systems had shifted poleward”

24 February 2020 (AWI) – In the course of the past 40 years, the major wind-driven current systems in the ocean have steadily shifted toward the poles. Experts at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), came to this conclusion after analysing long-term global satellite data on the ocean surface […]

May 27, 2019

Summer extremes of 2018 linked to stalled giant waves in jet stream

29 April 2019 (PIK) – Record breaking heatwaves and droughts in North America and Western Europe, torrential rainfalls and floods in South-East Europe and Japan – the summer of 2018 brought a series of extreme weather events that occurred almost simultaneously around the Northern Hemisphere in June and July. These extremes had something in common, […]