Atlantic Water (AW) transported from the Nordic Seas is the major source of oceanic heat to the Arctic Ocean. Based on results from the TOPAZ reanalysis, a regional coupled ice‐ocean data assimilation system, we show that interannual variability of AW temperature in the Fram Strait (FS) is associated with the strength of the Greenland Sea gyre (GSG) circulation. The response of the GSG to the anomalous wind stress curl over the Nordic Seas modifies the AW inflow and thus influences the variability of AW temperature in the FS. A stronger (weaker) GSG circulation increases (decreases) the AW flow speed toward FS, leading to increased (decreased) oceanic heat content and higher (lower) AW temperature therein. This implies that the Nordic Seas circulation is not only a passive conduit of AW, but its response to overlying atmospheric variability can also largely influence the AW temperature in the FS by modifying the transport of AW.

Under the influence of recent global warming, modulation of frequencies and amplitude of El Niño-Southern Oscillation (ENSO) and its impacts on global climate have become great concerns to the global community. Antarctic climate is sensitive to these changes owing to tropical and Southern Hemispheric (SH) teleconnections. Antarctic surface air temperature (SAT) reconstructed approximately for the past five centuries (~1533 to 1993 CE) based on multiple oxygen isotope (δ 18 O) records of ice cores from East and West Antarctica show dominant oscillations in ENSO and Pacific Decadal Oscillation (PDO) frequency bands. Further, variance of the East Antarctica (EA) temperature record shows significant increasing trend at ENSO band and decreasing trend at PDO band since the industrial era (~1850 CE). This observation is consistent with the earlier report of increasing ENSO activity, reconstructed based on tropical-subtropical tree ring records. ENSO influence in the SH high-latitude is known to be characterized by Pacific South American (PSA) pattern reflected in the atmospheric pressure fields. Our investigation of greenhouse gas (GHG) forced model simulation results show an increasing trend in PSA activity since the industrial era. Thus, we suggest ENSO activity and its influence on Antarctic temperature are increasing in response to increasing radiative GHG forcing since the industrial era.

Abstract. The Arctic Front (AF) in the Norwegian Sea is an important biologically productive region which is well-known for its large feeding schools of pelagic fish. A suite of satellite data, a regional coupled ocean–sea ice data assimilation system (the TOPAZ reanalysis) and atmospheric reanalysis data are used to investigate the variability in the lateral and vertical structure of the AF. A method, known as “singularity analysis”, is applied on the satellite and reanalysis data for 2-D spatial analysis of the front, whereas for the vertical structure, a horizontal gradient method is used. We present new evidence of active air–sea interaction along the AF due to enhanced momentum mixing near the frontal region. The frontal structure of the AF is found to be most distinct near the Faroe Current in the south-west Norwegian Sea and along the Mohn Ridge. Coincidentally, these are the two locations along the AF where the air–sea interactions are most intense. This study investigates in particular the frontal structure and its variability along the Mohn Ridge. The seasonal variability in the strength of the AF is found to be limited to the surface. The study also provides new insights into the influence of the three dominant modes of the Norwegian Sea atmospheric circulation on the AF along the Mohn Ridge. The analyses show a weakened AF during the negative phase of the North Atlantic Oscillation (NAO−), even though the geographical location of the front does not vary. The weakening of AF during NAO− is attributed to the variability in the strength of the Norwegian Atlantic Front Current over the Mohn Ridge associated with the changes in the wind field.

Abstract. Winds measured by lidar from the Aeolus satellite are compared with winds measured by two ground-based radars – MARA in Antarctica (70.77∘ S, 11.73∘ E) and ESRAD (67.88∘ N, 21.10∘ E) in Arctic Sweden – for the period 1 July–31 December 2019. Aeolus is a demonstrator mission to test whether winds measured by Doppler lidar from space can have sufficient accuracy to contribute to improved weather forecasting. A comprehensive programme of calibration and validation has been undertaken following the satellite launch in 2018, but, so far, direct comparison with independent measurements from the Arctic or Antarctic regions have not been made. The comparison covers heights from the low troposphere to just above the tropopause. Results for each radar site are presented separately for Rayleigh (clear) winds, Mie (cloudy) winds, sunlit (“summer”) and non-sunlit (“winter”) seasons, and ascending and descending satellite tracks. Horizontally projected line-of-sight (HLOS) winds from Aeolus, reprocessed using baseline 2B10, for passes within 100 km of the radar sites, are compared with HLOS winds calculated from 1 h averaged radar horizontal wind components. The agreement in most data subsets is very good, with no evidence of significant biases (<1 m s−1). Possible biases are identified for two subsets (about −2 m s−1 for the Rayleigh winds for the descending passes at MARA and about 2 m s−1 for the Mie winds for the ascending passes at ESRAD, both in winter), but these are only marginally significant. A robust significant bias of about 7 m s−1 is found for the Mie winds for the ascending tracks at MARA in summer. There is also some evidence for increased random error (by about 1 m s−1) for the Aeolus Mie winds at MARA in summer compared to winter. This might be related to the presence of sunlight scatter over the whole of Antarctica as Aeolus transits across it during summer.

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