Variability of the Northern Annular Mode's signature in winter sea ice concentration

Historical winter sea ice concentration data are used to examine the relation between the Northern Annular Mode (NAM) and the sea ice concentration in the Nordic seas over the past 50 years. The well known basic response pattern of a seesaw between the Labrador Sea and the Greenland, Iceland and Barents seas is being reproduced. However, the response is not robust in the Greenland and Iceland seas. There the observed variability has a more complex relationship with surface temperatures and winds. We divide the sea ice response into three spectral bands: high (P 15 year) filtered NAM indices. This division is motivated by the expected slow response of the ocean circulation which might play a significant role in the Greenland and Iceland seas. The response to the NAM is also examined separately for the periods before and after 1976 to identify variations due to the relocation of the northern centre of the North Atlantic Oscillatio

Variability of Internally Generated Turbulence in an Estuary, from 100 Days of Continuous Observations

We present detailed observations of internally generated turbulence in a sheared, stratified natural flow, as well as an analysis of the external factors leading to its generation and temporal variability. Multi-month time series of vertical profiles of velocity, acoustic backscatter (0.5 Hz), and turbulence parameters were collected with two moored acoustic Doppler current profilers (ADCPs) in the Hudson River estuary, and estuary-long transects of water density were collected 30 times. ADCP backscatter is used for visualization of coherent turbulent structures and evaluation of surface wave biases to the turbulence measurements. Benefits of the continuous long-term turbulence record include our capturing: (1) the seasonality of turbulence due to changing riverflow, (2) hysteresis in stratification and turbulence over the fortnightly cycle of tidal range, and (3) intermittent events such as breaking internal waves. Internal mixing layers (IMLs) are defined as turbulent regions above the logarithmic velocity layer, and the bottom boundary layer (BBL) is defined as the continuously turbulent range of heights above the bed. A cross-correlation analysis reveals how IML and BBL turbulence vary with stratification and external forcing from tidal range, river flow, and winds. Turbulence in both layers is maximal at spring tide and minimal when most stratified, with one exception IML turbulence at a site with changing channel depth and width is maximal at times of maximum stratification and freshwater input

3. Wochenbericht M105

(17.03.2014 – 16.04.2014

Oxygen in the Tropical Atlantic OSTRE Third Tracer Survey: Cruise No. M116/1

May 1 – June 3, 2015, Pointe-a-Pitre (Guadeloupe) – Mindelo (Cape Verde) OSTRE I

Oxygen in the Tropical Atlantic OSTRE Second Tracer Survey: Cruise No. M105

March 17 – April 16, 2014 Mindelo (Cape Verde) – Mindelo (Cape Verde

3. Wochenbericht M105

(17.03.2014 – 16.04.2014

3. Wochenbericht M116

3. Wochenbericht vom 17. Mai 2015 - M116 (01.05.2015 - 03.06.2015

2. Wochenbericht M133

M133 (15.12.2016 – 13.01.2017) 2. Wochenbericht vom 24. Dez. 201

2. Wochenbericht MSM10/1

Nach sieben Monaten kehrt das deutsche Forschungsschiff MARIA S. MERIAN in die Gewässer südlich der Kapverdischen Inseln zurück. Dort werden Wissenschaftler des Leibniz-Instituts für Meereswissenschaften (IFM-GEOMAR) vom 1. November bis 6. Dezember untersuchen, wohin die Wassermassen getrieben worden sind, die sie im April 2008 im Rahmen des Sonderforschungsbereichs (SFB) 754 mit chemische Markersubstanzen markiert hatten. Die Ergebnisse lassen Rückschlüsse über die Zirkulation und die Vermischung im Ozean nahe der riesigen Sauerstoffminimumzone vor der Küste von Guinea zu. In einem Weblog berichten die Wissenschaftler regelmäßig über ihre Arbeit. MSM 10/1 (31.10.2008 – 06.12.2008) 2. Wochenbericht vom 9. Nov. 0