Description: Considerable advances in the global ocean observing system over the last two decades offers an opportunity to provide more quantitative information on changes in heat and freshwater storage. Variations in these storage terms can arise through internal variability and also the response of the ocean to anthropogenic climate change. Disentangling these competing influences on the regional patterns of change and elucidating their governing processes remains an outstanding scientific challenge. This challenge is compounded by instrumental and sampling uncertainties. The combined use of ocean observations and model simulations is the most viable method to assess the forced signal from noise and ascertain the primary drivers of variability and change. Moreover, this approach offers the potential for improved seasonal-to-decadal predictions and the possibility to develop powerful multi-variate constraints on climate model future projections. Regional heat storage changes dominate the steric contribution to sea level rise over most of the ocean and are vital to understanding both global and regional heat budgets. Variations in regional freshwater storage are particularly relevant to our understanding of changes in the hydrological cycle and can potentially be used to verify local ocean mass addition from terrestrial and cryospheric systems associated with contemporary sea level rise. This White Paper will examine the ability of the current ocean observing system to quantify changes in regional heat and freshwater storage. In particular we will seek to answer the question: What time and space scales are currently resolved in different regions of the global oceans? In light of some of the key scientific questions, we will discuss the requirements for measurement accuracy, sampling, and coverage as well as the synergies that can be leveraged by more comprehensively analysing the multi-variable arrays provided by the integrated observing system.

Description: The ice shelf water (ISW) found in the Filchner Trough, located in the southern Weddell Sea, Antarctica, is climatically important; it descends into the deep Weddell Sea contributing to bottom water formation, and it blocks warm off‐shelf waters from accessing the Filchner ice shelf cavity. Yet the circulation of ISW within the Filchner Trough and the processes determining its exchange across the ice shelf front are to a large degree unknown. Here mooring records from the ice shelf front are presented, the longest of which is 4 years long. They show that the coldest (Θ =− 2.3∘C) ISW, which originates from the Ronne Trough in the west, exits the cavity across the western part of the ice shelf front during late austral summer and early autumn. The supercooled ISW escaping the cavity flows northward with a velocity of about 0.03 m/s. During the rest of the year, there is no outflow at the western site: the current is directed eastward, parallel to the ice shelf front, and the temperatures at the mooring site are slightly higher (Θ =− 2.0∘C). The eastern records show a more persistent outflow of ISW.

Description: Time series data of physical oceanography (seawater conductivity, temperature, pressure, salinity) were obtained from mooring M3 on the upper part (750 m isobath) of the continental slope, just east of the Filchner Trough in the southern Weddell Sea in February 2017 - February 2021. The mooring was deployed during the WAPITI expedition on James Clark Ross (JR16004), and recovered during the COSMUS expedition with Polarstern (PS124). The attached archive contains data from 1 RCM7 (21 meters above bottom (mab herafter) and sampling interval (sint hereafter) 2h), 13 SBE56 (22,56,81,106,159,184,6508,260,285,310,335,360,385 mab, sint: 120 s), 4 SBE37 (31, 134, 209, 410 mab, sint: 600 s), 1 SBE39 (435 mab, sint: 900s). Mooring diagrams and information about data processing are provided.

Description: Time series data of ocean current velocities were obtained from mooring M3 on the upper part (750 m isobath) of the continental slope, just east of the Filchner Trough in the southern Weddell Sea in February 2017 - February 2021. The mooring was deployed during the WAPITI expedition on James Clark Ross (JR16004), and recovered during the COSMUS expedition with Polarstern (PS124). The attached archive contains data from 1 RDI ADCP 75 kHz (235 mab, upwardlooking, with sampling intervall: 2h. Mooring diagrams and information about data processing are provided.

Description: Time series data of physical oceanography (seawater conductivity, temperature, pressure, salinity) and ocean current velocities were obtained from mooring M6 on the upper part (500 m isobath) of the continental slope, just east of the Filchner Trough in the southern Weddell Sea in February 2017 - February 2021. The mooring was deployed during the WAPITI expedition on James Clark Ross (JR16004), and recovered during the COSMUS expedition with Polarstern (PS124). The attached archive contains data from 1 RCM7 (24 meters above bottom (mab herafter) and sampling interval (sint hereafter) 2h), 5 SBE56 (25, 59, 74, 126, 202 mab, sint: 120 s), 3 SBE37 (34, 99, 176 mab, sint: 600 s), 1 RDI ADCP 150 kHz (235 mab, upwardlooking, sint: 1h), 1 SBE39 (15 mab, sint: 900s). Mooring diagrams and information about data processing are provided