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The interannual variability in fluorescent dissolved organic matter (FDOM) was assessed in the Pacific‐ and Atlantic‐derived halocline, and Atlantic waters (AWs) of the Canada Basin during late summer/early fall expeditions in 2007–2017. Fluorescence spectroscopy excitation‐emission matrices coupled with parallel factor analysis were used to validate a seven‐component model. During the 11 years, humic‐like intensities increased by 0.0002–0.0006 r.u. (Raman unit) (p < 0.05) with greater annual rates of change in shallower waters (i.e., Pacific summer water) than in deeper waters (i.e., AWs). No significant temporal trends were observed for protein‐like intensities in any water layer (p > 0.05) due to the labile nature of these components. The increases in humic‐like fluorescence intensities were likely the results of changes in Bering Strait inflow and its modification over the Chukchi Shelf and/or the accumulation of freshwater under anticyclonic wind forcing in the Beaufort gyre. This 11‐year late summer/early fall survey shows the first evidence of changes in FDOM composition in the halocline of the Arctic Ocean basin. Plain Language Summary: The highly stratified Arctic Ocean receives a disproportionate amount of freshwater and plays a large role in the regulation of the global climate. Over the last decade, the effects of sea ice decline, hydrological cycle intensification, and vertical stratification have strengthened. Dissolved organic matter (DOM) is a heterogeneous mixture of non‐living organic compounds and is central to the marine carbon cycle. This study, which is part of the Joint Ocean Ice Study/Arctic Observing Network—Beaufort Gyre Observing System program, aims to assess the level and composition of fluorescent dissolved organic matter (FDOM) in water samples collected in the dark Canada Basin waters of the Arctic Ocean in late summer/early autumn between 2007 and 2017. The results of the present study indicate that microbial activity constitutes a significant source of humic‐like FDOM in the Atlantic—derived halocline waters. During the 11 years, the humic‐like component levels increased in both the Pacific and Atlantic‐origin halocline waters, which were likely the results of changes in Bering Strait inflow, heat transfer over the Chukchi Sea shelves, and/or the accumulation of FDOM‐rich freshwater under clockwise wind forcing in the Beaufort gyre. Key Points: Statistically significant temporal increases were observed in humic‐like fluorescence intensities in the halocline watersIncreases in halocline humic‐like reflect changes in Pacific‐origin flow, organic input, and, Chukchi shelf and advection processesEvidence of in situ microbial production of humic‐like fluorescence was found in the Atlantic‐origin halocline [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) absorption and fluorescence properties were investigated for seawater samples collected from the polar mixed layer (0–30 m) of the Canada Basin in 2010–2012. Sea ice concentration as well as fractions of meteoric and sea ice meltwater (fMW and fSIM) calculated from oxygen isotope ratio (δ18O) were applied to assess the importance of discrete freshwater inputs to the distribution of DOM. Parallel factor analysis identified four humic‐like (C1‐2 and C4‐C5) and one protein‐like (C3) fluorescent components in 380 excitation‐emission matrix spectra. Surprisingly, despite different sea ice cover and biological regimes, DOM composition was largely homogeneous spanning these annual surveys. A strong and reoccurring coastal influence on DOM absorption and humic‐like DOM was observed each year and was particularly pronounced during the summer 2011 survey. Enrichment of DOM humic signal (C1, C2, and C4) in brine‐rich (fSIM < 0) waters relative to sea ice melt‐dominated waters (fSIM > 0; p < 0.05) was found during 2011 and 2012 in the offshore region (>76°N) where coastal influences were minimal (fMW < 0.1). Similar fSIM < 0 were found for 2011 and 2012, either when considering the Canada Basin as a whole or the offshore region (>76°N) exclusively, which could imply that brine formation influenced humic signals in polar mixed layer seawater. Findings herein highlight that future projected changes in freshwater sources and brine production in the Canada Basin will likely implicate the distribution and composition of DOM. Plain Language Summary: In this paper we showed that despite different sea ice cover in summer‐early fall, the average levels and composition of colored dissolved organic matter remained relatively unchanged in surface waters in the Canada Basin in 2010–2012. Only the northwest region experiencing strong brine rejection showed elevated humic signals. We also suggest to use the 140°W line as reference for dissolved organic matter monitoring in the Canada Basin in future studies. Key Points: The absorption and fluorescing characteristics of DOM were relatively homogenous in the Canada Basin in summer/early fall 2010–2012The humic‐like components were more abundant in the brine‐rich mixed layerThe 140°W line is proposed for monitoring DOM compositional changes in the Canada Basin [ABSTRACT FROM AUTHOR]

Abstract: Position and velocity data are analyzed from a release of surface ocean drifters in the Arctic Ocean's Beaufort Sea in ice‐free conditions. Position information is returned at sufficiently high frequency to allow for the investigation of surface‐ocean flows ranging from around 0.5 km in lateral scale (submesoscale, SM, flows) to flows that are tens of kilometers in horizontal extent. Lagrangian statistics from the drifter release are analyzed in conjunction with Eulerian (ship‐based) measurements of surface ocean temperature and salinity. Results show dynamics that are largely consistent with flows at similar scales in the midlatitude oceans. Horizontal wavenumber k spectra of density in the surface ocean scale as k − 2, consistent with energetic SM flows. Lagrangian drifters indicate local dispersion in the surface ocean layer at horizontal scales smaller than 10 km, which confirms the presence of active submesoscale dynamics. Features at these scales give rise to lateral diffusivities (in the range 1–103 m2 s−1) of similar range to values inferred in the midlatitudes. Velocity structure functions present an energy‐cascade inertial range at submesoscales with indication of a transition to a forward energy cascade at scales smaller than 1 km confirming the transition to 3‐D turbulence. The active SM flow‐field drives enhanced lateral and vertical fluxes in the Arctic Ocean mixed layer, which has first‐order implications to the transport of heat, sea‐ice floes, nutrients, and contaminants. [ABSTRACT FROM AUTHOR]

summary There are conflicting opinions about the frequency range of temporomandibular joint (TMJ) sounds. Some authors claim that the upper limit is about 650 Hz. The aim was to test the hypothesis that TMJ sounds may contain frequencies well above 650 Hz but that significant amounts of their energy are lost if the vibrations are recorded using contact sensors and/or travel far through the head tissues. Time–frequency distributions of 172 TMJ clickings (three subjects) were compared between recordings with one microphone in the ear canal and a skin contact transducer above the clicking joint and between recordings from two microphones, one in each ear canal. The energy peaks of the clickings recorded with a microphone in the ear canal on the clicking side were often well above 650 Hz and always in a significantly higher area (range 117–1922 Hz, P < 0·05 or lower) than in recordings obtained with contact sensors (range 47–375 Hz) or in microphone recordings from the opposite ear canal (range 141–703 Hz). Future studies are required to establish normative frequency range values of TMJ sounds but need methods also capable of recording the high frequency vibrations. [ABSTRACT FROM AUTHOR]

summary Differential diagnosis depends in cases with disk displacement on accurate identification of sound source. Mistakes may occur when clicking from one temporomandibular joint (TMJ) is heard on both sides of the head at auscultation and neither examiner nor patient, is sure about side. The hypothesis was that the head tissues affect spectral characteristics of TMJ sounds and that differences due to different positioning of sensors can be used in localization of source. The aim was to compare bilateral electronic recordings of unilateral TMJ sounds to obtain and compare attenuation, phase shift and time delay. Recordings were made from 12 subjects with unilateral clicking. Small electret condenser microphones, bandwidth 40–20 000 Hz, were placed at the openings of the auditory canals and the sounds were recorded at a sampling rate of 48 000 Hz. The head tissues acted as a filter causing a frequency dependent attenuation and phase shift. There was a time difference between the ipsi- and the contra lateral recordings, the latter always having a longer delay time (range 0·2–1·2 ms, group mean 0·68 ms, s.d. 0·292 ms). In conclusion, spectral analysis of bilateral electronic TMJ sound recordings is of diagnostic value when bilateral clicking is heard at auscultation and can help to avoid diagnosing a silent joint as clicking. [ABSTRACT FROM AUTHOR]

The aim of the present study was to determine the sound wave forms which correspond to auscultatory findings of temporomandibular joint (TMJ) clicking and crepitation. Such knowledge is important when selecting parts of digital recordings for spectral analysis. Electronic digital recordings were made with a sampling rate of 44 100 Hz from 60 subjects, including 51 patients referred for suspected rheumatological disease and nine healthy subjects. Accelerometers with the bandwidth 20-3600 Hz were used for all subjects and complementary recordings were made from a subgroup of nine subjects using a measurement microphone with the bandwidth 20-20000 Hz. The clicking sounds could be classified into different types according to differences in temporal period duration (T) as measured on the analogue display. One type of clicking, found in 51% of the patients, had a T of 2-20 ms. Another type, found in 70% of the subjects, had a T of less than 1 ms, often as low 0.2 ms. This type of clicking was not seen at all in the analogue display if the sampling rate was below 3 000 Hz. The character of the two types of clicking differed: the short duration sounds had a very high pitch, while the pitch of the longer duration sound was lower. Crepitation was found in 63% of the subjects and was observed to be composed of a series of short duration sounds, occurring with brief (less than 10 ms) intervals. It is concluded that the accelerometer (or microphone) bandwidth should cover the entire audible range (2 0-20000 Hz), and that sampling rates must be much higher than 3000 Hz, and preferably greater than 10000 Hz, before the true significance of electronically recorded joint sounds/ vibrations can be determined. [ABSTRACT FROM AUTHOR]

Temporomandibular joint (TMJ) sounds were recorded in 98 orthodontic retention patients, mean age 19±8.6 (s.d.) years, by interview, auscultation and electronic recording. Sounds were found by auscultation in 41% and by interview in 32% of the subjects, more often in females than in males (P < 0.05). A new method for time-frequency analysis, the reduced interference distribution (RID), was used to classify the electronic sound recordings into five subclasses, RID types 1-5, based upon location and number of their energy peaks. RID types 1-3 had a few energy peaks close in time. RID types 4-5, typical of subjects with crepitation, had multiple energy peaks occurring close in time for a period of 20- 300 ms. RID type 1, found in 45% of the subjects, typical of patients with clicking, had its dominant energy peak located in a frequency range <600 Hz and was significantly more common in the female than in the male subjects (P < 0.01). RID type 2, found in 68% of the subjects, with the dominant peak in the range 600-1200 Hz, and RID type 3, found in 38% of the subjects, with the peak in the frequency range >1200 Hz, were found to have a similar gender distribution. RID type 4, found in 49% of the subjects, had the energy peaks distributed in the frequency range <600 Hz. RID type 5, found in 43% of the subjects, more often in females than in males (P < 0.05), had the peaks distributed over the whole frequency range from about 30 Hz up to about 3000 Hz. In conclusion, a more detailed classification could be made of the TMJ sounds by displaying the RIDs than by auscultation. This suggests that RID classification methods may provide a means for differentiating sounds indicating different types of pathology. [ABSTRACT FROM AUTHOR]

For analysis of time-varying signals such as the TMJ sounds, it is often desirable to know how the frequency components change with time, using methods of time-frequency analysis. The aim of this study was to compare two of the most familiar methods for energy density representation with a newly developed technique. The sounds were recorded with a microphone fastened to the subject's forehead, transformed to the time-frequency domain and displayed as 3D- and contour plots using spectrogram, Wigner distribution (WD), and the reduced interference distribution (RID) to display their time-frequency energy distributions. The spectrogram resolved only the low-frequency components. The WD provided higher resolution but also exhibited strong interference between components. The RID gave a detailed representation of the TMJ signals' relative energy distribution in the time and frequency domains, with a great reduction in the interference or cross terms. The RID therefore appears to be most useful in the application of time-frequency distributions in classification of TMJ sounds. [ABSTRACT FROM AUTHOR]

Discusses the importance of the localization of temporomandibular (TMD) sounds in temporomandibular joint disease diagnosis. Comparison of bilateral recordings of unilateral sounds to estimate the head tissues' filtering effects; Results indicating that head tissues act as a band filter; Frequency variations in attenuation of transmitted sounds.