P Reid

Snow on Antarctic sea ice

Snow on Antarctic sea ice plays a complex and highly variable role in air-sea-ice interaction processes and the Earths climate system. Using data collected mostly during the past 10 years, this paper reviews the following topics: snow thickness and snow type and their geographical and seasonal variations; snow grain size, density, and salinity; frequency of occurrence of slush; thermal conductivity, snow surface temperature, and temperature gradients within snow; and the effect of snow thickness on albedo. Major findings include large regional and seasonal differences in snow properties and thicknesses; the consequences of thicker snow and thinner ice in the Antarctic relative to the Arctic (e.g., the importance of flooding and snow-ice formation); the potential impact of increasing snowfall resulting from global climate change; lower observed values of snow thermal conductivity than those typically used in models; periodic large-scale melt in winter; and the contrast in summer melt processes between the Arctic and the Antarctic. Both climate modeling and remote sensing would benefit by taking account of the differences between the two polar regions.

Change and Variability in East Antarctic Sea Ice Seasonality, 1979/80–2009/10

Recent analyses have shown that significant changes have occurred in patterns of sea ice seasonality in West Antarctica since 1979, with wide-ranging climatic, biological and biogeochemical consequences. Here, we provide the first detailed report on long-term change and variability in annual timings of sea ice advance, retreat and resultant ice season duration in East Antarctica. These were calculated from satellite-derived ice concentration data for the period 1979/80 to 2009/10. The pattern of change in sea ice seasonality off East Antarctica comprises mixed signals on regional to local scales, with pockets of strongly positive and negative trends occurring in near juxtaposition in certain regions e.g., Prydz Bay. This pattern strongly reflects change and variability in different elements of the marine “icescape”, including fast ice, polynyas and the marginal ice zone. A trend towards shorter sea-ice duration (of 1 to 3 days per annum) occurs in fairly isolated pockets in the outer pack from∼95–110°E, and in various near-coastal areas that include an area of particularly strong and persistent change near Australias Davis Station and between the Amery and West Ice Shelves. These areas are largely associated with coastal polynyas that are important as sites of enhanced sea ice production/melt. Areas of positive trend in ice season duration are more extensive, and include an extensive zone from 160–170°E (i.e., the western Ross Sea sector) and the near-coastal zone between 40–100°E. The East Antarctic pattern is considerably more complex than the well-documented trends in West Antarctica e.g., in the Antarctic Peninsula-Bellingshausen Sea and western Ross Sea sectors.

Advancing Polar Prediction Capabilities on Daily to Seasonal Time Scales

AbstractThe polar regions have been attracting more and more attention in recent years, fueled by the perceptible impacts of anthropogenic climate change. Polar climate change provides new opportunities, such as shorter shipping routes between Europe and East Asia, but also new risks such as the potential for industrial accidents or emergencies in ice-covered seas. Here, it is argued that environmental prediction systems for the polar regions are less developed than elsewhere. There are many reasons for this situation, including the polar regions being (historically) lower priority, with fewer in situ observations, and with numerous local physical processes that are less well represented by models. By contrasting the relative importance of different physical processes in polar and lower latitudes, the need for a dedicated polar prediction effort is illustrated. Research priorities are identified that will help to advance environmental polar prediction capabilities. Examples include an improvement of the p...

Clozapine rechallenge after myocarditis

Philip Reid, Milford McArthur and Saxby Pridmore, Department of Psychological Medicine, Royal Hobart Hospital, Hobart, Australia: We present a case of clozapine rechallenge after myocarditis. Recently, the frequency of the side-effect of myocarditis from clozapine has been reported at a higher level than was once thought; Australian data suggests an incidence of one in five hundred in the first month [1]. This has prompted recommendations for further monitoring in the form of regular electrocardiograms (ECG), echocardiograms and blood tests. This monitoring is likely to detect subclinical cases. Clinicians will increasingly face the difficult decision of discontinuation when interpreting the significance of more subtle ECG changes. In June 1994, a 23-year-old former university student with deteriorating, treatment-resistant schizophrenia was started on clozapine. He had no history of cardiac disease or alcoholism and was physically fit. Clozapine was begun at 12.5 mg and increased slowly to 200 mg over 3 weeks. Initially, he exhibited the side-effects of hypersalivation, mild sedation and some dizziness from hypotension but these passed with time. His mental state improved significantly with a reduction of his positive symptoms. He was discharged on clozapine only and attended an outpatient clinic with regular blood testing. Five weeks after starting clozapine, he complained of shortness of breath and non-specific aches and pains in his legs and body. On examination, he had a regular pulse of 120 beats/min, but no signs of heart failure. An ECG was taken which revealed marked ST-depression and T-wave inversion in the lateral and inferior leads. Eosinophilia was absent and creatine kinase was not elevated. Echocardiogram showed a hyperdynamic heart with left ventricular chamber size at the upper limit of normal. Heart valves and function were reported as normal. A consultant cardiologist diagnosed myocarditis secondary to clozapine as no other confounding comorbidity was identified. The clozapine was ceased, but a deterioration in his mental state with thought-blocking and grimacing ensued 2 weeks after ceasing the medication. He started on resperidone which was later augmented with lithium. However, he continued to deteriorate, with marked anhedonia, alogia, amotivation and blunting of affect. A trial of haloperidol did not lead to any obvious improvement. In 1996 clozapine was resumed. This decision was made after consultation with the patient, his family and the cardiologist who had made the diagnosis of myocarditis in 1994. Because of his steady decline in mental state and poor quality of life, another trial of clozapine was attempted with weekly ECG and eosinophil counts. Repeat echocardiogram prior to the commencement of clozapine was normal, apart from the trivial mitral regurgitation. His ECG had improved but still had evidence of T-wave flattening and ST depression. The dose of clozapine was built up to a dose of 225 mg at night, his ECG remained unchanged and there was no rise in eosinophils. Again, his symptoms and functioning improved significantly over the initial 2 months with further subtle but significant positive change over years. He remains well and free of cardiac side-effects. Myocarditis is a difficult condition to define and diagnose even with endocardial biopsy [2]. The pathophysiology of clozapine myocarditis is not known and complicated by the high likelihood of previous antipsychotic exposure. However IgE-mediated hypersensitivity, type 3 allergic reaction and direct toxic effects have been postulated in its aetiology [1]. Australian figures suggest clozapine-associated myocarditis is most likely to occur within the first 3 weeks of therapy. In the present case, symptoms developed in the sixth week. There are reports of numerous organ systems including the cardiovascular system being involved in clozapine-induced allergy which is invariably associated with eosinophilia [3]. The lack of eosinophilia and the later timing of the episode may suggest a toxic rather that allergic response in this patient. Some suggest that the ultimate test for causality of a drug reaction is dechallenge followed by rechallenge [4], thereby ruling out clozapine in this case. However, the timing and ECG findings, together with cardiology opinion, suggested this to be clozapine-induced myocarditis at the time of discontinuation. This case highlights the significant and unique contribution that clozapine can make to some individuals with treatment-resistant schizophrenia. For this patient quality of life improvement outweighed the risk of further clozapine therapy. This is the first reported case of rechallenge of clozapine after myocarditis. It was achieved after considering the risk benefit, receiving the informed consent of the patient and with close cardiac monitoring.

Dexamethasone suppression test reversal in rapid transcranial magnetic stimulation‐treated depression

Objective: The aim of this paper is to report the effect of rapid transcranial magnetic stimulation (rTMS) on the mood and dexamethasone suppression test (DST) of a patient with major depressive disorder (DSM-IV). Clinical picture: A36-year-old woman with a past history of prolactinoma and recurrent major depressive disorder presented with major depression on three separate occasions over a 3-month period. DST was positive on each occasion. Treatment: During each episode, a course of rTMS was given. Courses varied from seven to 13 once-daily treatment sessions depending on clinical response. These treatment sessions were 20 trains of 10 Hz for 5 s at 100% of motor threshold. Outcome: Remission was achieved, psychiatric rating scales improved and the DST status converted from positive to negative. There were no side effects. Conclusion: DST status in major depressive disorder can be converted from positive to negative by rTMS. This so far unreported observation increases our knowledge of rTMS.

Cortical excitability of psychiatric disorders: reduced post-exercise facilitation in depression compared to schizophrenia and controls.

Objective: In normal subjects, motor evoked potentials (MEPs) produced by transcranial magnetic stimulation (TMS) from the motor cortex are increased after non-fatiguing exercise of hand muscles. This phenomenon is called post-exercise facilitation. This study aims to test the hypothesis that psychiatric syndromes (major depressive episode, schizophrenia) have different levels of post-exercise facilitation compared to controls. Methods: Patients with DSM-IV major depressive episode (six female, four male), schizophrenia (two female, nine male) and a control group (nine female, four male) participated. MEPs were elicited pre- and post-exercise from the contralateral abductor pollicis brevis by TMS over the primary motor cortex. Results: Post-exercise facilitation expressed as a percentage of baseline was 510% in controls, 110% in depression and 190% in schizophrenia. There were significant differences in patients with depression and schizophrenia compared to controls (p = 0.0001, p = 0.0008). Conclusions: Post-exercise facilitation was reduced in depression and schizophrenia, suggesting impaired cortical excitability in these disorders. Further studies may discriminate between the two groups.

Variability in sea ice cover and climate elicit sex specific responses in an Antarctic predator

Contrasting regional changes in Southern Ocean sea ice have occurred over the last 30 years with distinct regional effects on ecosystem structure and function. Quantifying how Antarctic predators respond to such changes provides the context for predicting how climate variability/change will affect these assemblages into the future. Over an 11-year time-series, we examine how inter-annual variability in sea ice concentration and advance affect the foraging behaviour of a top Antarctic predator, the southern elephant seal. Females foraged longer in pack ice in years with greatest sea ice concentration and earliest sea ice advance, while males foraged longer in polynyas in years of lowest sea ice concentration. There was a positive relationship between near-surface meridional wind anomalies and female foraging effort, but not for males. This study reveals the complexities of foraging responses to climate forcing by a poleward migratory predator through varying sea ice property and dynamic anomalies.

Seasonal climate summary southern hemisphere (spring 2012): warmer and drier across much of Australia, along with a new southern hemisphere sea ice extend record

Atmospheric, oceanic and sea ice conditions in the southern hemisphere are reviewed for the austral spring of 2012, with emphasis given to the Pacific basin climate indicators and Australian rainfall and temperature patterns. The Pacific basin saw a return to neutral ENSO conditions, with slightly warmer than normal equatorial SSTs just east of the date line and neutral SOI and multivariate ENSO indices. The Australian rainfall pattern was indicative of a positive Indian Ocean Dipole, with much of South Australia and other eastern Australian States experiencing much drier than normal conditions. Much of Western Australia, however, had a wetter than normal spring. November 2012 saw much of Australia’s east and south experience one of the most significant spring heatwaves on record which, together with the dry conditions, would leave this area of the continent vulnerable to summer bushfires. Particularly strong cyclonic activity in the Ross Sea and off Queen Maud Land saw southern hemisphere sea ice reach a new record extent in September 2012 of approximately 19.45 million km2.

Spatiotemporal dependence of Antarctic sea ice variability to dynamic and thermodynamic forcing: a coupled ocean–sea ice model study

Satellite-derived Antarctic sea ice extent has displayed a slight upward since 1979, but with strong temporal and regional variability—the drivers of which are poorly understood. Here, we conduct numerical experiments with a circum-Antarctic ocean–sea ice–ice shelf model driven by realistic atmospheric surface boundary conditions to examine the factors responsible for the temporal and spatial patterns in observed Antarctic sea ice variability. The model successfully reproduces observed seasonal and interannual variability in total sea ice extent and the temporal/spatial patterns of sea ice concentration and seasonality (days of advance and retreat and actual ice days) for 1979–2014. Sensitivity experiments are performed, in which the interannual variability in wind stress or thermodynamic surface forcing is ignored, to delineate their contributions to Antarctic sea ice fields. The results demonstrate that: (1) thermodynamic forcing plays a key role in driving interannual variability in sea ice extent and seasonality in most Antarctic sectors; (2) only in the Ross Sea the wind stress does become the main driver of sea ice extent variability; (3) thermodynamic forcing largely regulates interannual variability in the timing of sea ice advance, while wind stress largely controls the timing of the sea ice retreat; and (4) although both wind stress and thermodynamic forcing contribute to variability in total sea ice volume, the wind stress plays a dominant role in regulating sea ice volume variability in the near-coastal zone.

Sea ice extent, concentration, and seasonality [in “State of the Climate in 2017”]

Observed lake surface water temperature anomalies in 2017 are placed in the context of the recent warming observed in global surface air temperature by collating long-term in situ lake surface temperature observations from some of the world’s best-studied lakes and a satellite-derived global lake surface water temperature dataset. The period 1996–2015, 20 years for which satellite-derived lake temperatures are available, is used as the base period for all lake temperature anomaly calculations.Antarctic sea ice performs important roles in the climate system through the formation of dense oxygen rich Antarctic Bottom Water (Johnson 2008) and modulating fluxes across the ocean/atmosphere interface within the high southern latitudes (Bourassa et al. 2013). It also acts as a buffer for ice shelves against ocean processes (Williams and Squire 2007; Massom et al. 2018).